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Internal mouthpiece designs as a future perspective for enhanced aerosol deposition. Comparative results for aerosol chemotherapy and aerosol antibiotics
International Journal of Pharmaceutics 456 (2013) 325–331
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International Journal of Pharmaceutics journal homepage: www.elsevier.com/locate/ijpharm
Personalised medicine
Internal mouthpiece designs as a future perspective for enhanced aerosol deposition. Comparative results for aerosol chemotherapy and aerosol antibiotics Paul Zarogoulidis a,b,∗ , Dimitris Petridis c , Christos Ritzoulis c , Kaid Darwiche b , Ioannis Kioumis a , Konstantinos Porpodis a , Dionysios Spyratos a , Wolfgang Hohenforst-Schmidt d , Lonny Yarmus e , Haidong Huang f , Qiang Li f , Lutz Freitag b , Konstantinos Zarogoulidis a a
Pulmonary Department-Oncology Unit, “G. Papanikolaou” General Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece Department of Interventional Pneumology, Ruhrlandklinik, West German Lung Center, University Hospital, University Duisburg-Essen, Essen, Germany Department of Food Technology, School of Food Technology and Nutrition, Alexander Technological Educational Institute, Thessaloniki, Greece d II Medical Department, “Coburg” Regional Clinic, University of Wuerzburg, Coburg, Germany e Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, USA f Department of Respiratory Diseases Shanghai Hospital, II Military University Hospital, Shanghai, China b c
a r t i c l e
i n f o
Article history: Received 17 August 2013 Received in revised form 3 September 2013 Accepted 5 September 2013 Available online 11 September 2013 Chemical compounds studied in this article: Aztreonam (PubChem CID: 5742832) Gentamycin (PubChem CID: 3467) Tobramycin (PubChem CID: 36294) Ciprofloxacin (PubChem CID: 2764) Cisplatin (PubChem CID: 84093) Carboplatin (PubChem CID: 10339178) Paclitaxel (PubChem CID: 36314) Docetaxel (PubChem CID: 148124) Gemcitabine (PubChem CID: 60750) Doxorubicin (PubChem CID: 31703)
a b s t r a c t Background: In an effort to identify factors producing a finest mist from Jet-Nebulizers we designed 2 mouthpieces with 4 different internal designs and 1–3 compartments. Materials and methods: Ten different drugs previous used with their “ideal” combination of jet-nebulizer, residual-cup and loading were used. For each drug the mass median aerodynamic diameter size had been established along with their “ideal” combination. Results: For both mouthpiece, drug was the most important factor due the high F-values (Flarge = 251.7, p < 0.001 and Fsmall = 60.1, p < 0.001) produced. The design affected the droplet size but only for large mouthpiece (Flarge = 5.99, p = 0.001, Fsmall = 1.72, p = 0.178). Cross designs create the smallest droplets (2.271) so differing from the other designs whose mean droplets were greater and equal ranging between 2.39 and 2.447. The number of compartments in the two devices regarding the 10 drugs was found not statistically significant (p-values 0.768 and 0.532 respectively). Interaction effects between drugs and design were statistically significant for both devices (Flarge = 8.87, p < 0.001, Fsmall = 5.33, p < 0.001). Conclusion: Based on our experiment we conclude that further improvement of the drugs intended for aerosol production is needed. In addition, the mouthpiece design and size play an important role in further enhancing the fine mist production and therefore further experimentation is needed. © 2013 Elsevier B.V. All rights reserved.
Keywords: Aerosol Mouthpiece Designs
1. Introduction Currently the main mode of administration for several therapies is the intravenous route. In the previous years an effort was
∗ Corresponding author at: “G. Papanikolaou” General Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece. Tel.: +49 15779211742; fax: +30 2130992433. E-mail addresses: [email protected], [email protected] (P. Zarogoulidis). 0378-5173/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ijpharm.2013.09.004
made to explore alternative routes of administration in order to enhance the efficiency of therapy and to minimize adverse effects. As it has been observed with several drugs, the adverse effects are directly related to the concentration administered (Miura et al., 2013). In several diseases the target lesion is located to a site which is difficult to approach directly and administer the optimal treatment. Therefore intravenous administration is administered in almost every disease. However; higher concentrations have to be delivered in older to have the desired result. In addition, the discomfort and adverse effects from the intravenous administration is another factor reducing the quality of life of patients (Baron et al.,
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2013; Wynne et al., 2013). The inhaled insulin was one of the first examples where a systematic therapy was redesigned to be administered as aerosol (Zarogoulidis et al., 2011). Inhaled antibiotics followed for patients with cystic fibrosis and patients admitted in the intensive care unit (Geller et al., 2007). Currently experimentation for lung cancer treatment is ongoing as local treatment in the form of intratumoral administration (endobronchial lesions) (Hohenforst-Schmidt et al., 2013), aerosol chemotherapy administration (Zarogoulidis et al., 2012a; Zarogoulidis et al., 2012b) and inhaled gene therapy (Zarogouldis et al., 2012; Zarogoulidis et al., 2013a; Zarogoulidis et al., 2012c). The safety of these novel treatment modalities is under investigation and currently several aerosol production systems are being developed (Darwiche et al., 2013; Zarogoulidis et al., 2013b; Zarogoulidis et al., 2013d). The main concept is to produce treatment administration modalities that are both effective and safe. In our previous work we divided the aerosol production methodology in two clusters: (i) the production system and (ii) the delivery system. We included in the production system the following parameters: (a) jet-nebulizer, (b) residual-cup design, (c) loading of residual-cup and (d) drug. We investigated the interaction of these four parameters between them to identify in what degree one affected the other. We identified for five chemotherapy drugs and five antibiotic drugs the “ideal” combination of these parameters producing the smallest droplets (mass median aerodynamic diameter < 5 m). In our current work we investigated the “delivery system” which is the connection between the residual-cup and upper airways. There are two “delivery systems” that are used nowadays; (a) face mask and (b) mouthpiece. (Fig. 1.) Each one has its advantages and disadvantages which will be analyzed in the discussion section (Lin et al., 2007b; Sangwan et al., 2004). In specific eighteen different mouthpieces were designed in order to evaluate whether this part of the aerosol delivery process affects the mist production and hence the performance. It has been previous investigated that factors such as; turbulence, inlet size, air flow, mouthpiece and
grid affect the production of the aerosol mist (Jiang et al., 2012). Inhaled insulin is an example again where different mouthpiece designs were investigated in an effort to enhance the aerosol production. Indeed the mouthpiece design was observed to be a key factor affecting the mist production at least for inhaled insulin (Boyd et al., 2004; Coates et al., 2007). The addition of a spacer has presented again favorable results when connected to a metered dose inhaler or jet-nebulizer production system (Silkstone et al., 2002). A third system identified to further influence the deposition of aerosol mist consists of the following geometrical factors; geometrical; mouth, oropharynx, larynx intra-thoracic airways up to six generations. The intra-thoracic airways however; is not a stable systems since the diameter changes due to underlying conditions (e.g. bronchoconstriction, excessive mucus production, viscosity of mucus) and diseases (e.g. chronic obstructive pulmonary disease, cystic fibrosis, asthma) (Lin et al., 2007a). The breathing pattern plays also an important role of aerosol deposition (Foust et al., 1991; Nikander et al., 2000). We will present our results and indicate future investigational directions towards the aerosol production methodology. 2. Materials and methods 2.1. Nebulizers Based on our previous experiments we identified that for chemotherapy drugs (Cisplatin, Paclitaxel, Docetaxel, Gemcitabine and Carboplatin) the “ideal” combination producing the smallest droplets (mass median aerodynamic diameter) was the nebulizer Maxineb® (6 l/min and 35 psi), residual cup D with 8 ml loading (Zarogoulidis et al., 2013d). Regarding the antibiotics the “ideal” combination was for zobactam the residual cup C and G with 6 ml loading, for solvetan residual cup D with 8 ml loading and for maxipine, begalin, meronem residual cup C with 6 ml loading. There was no difference observed between the nebulisers (a) Sunmist®
Fig. 1. (A) ISO-NEB® Filtered Nebulizer System, UP-DRAFT II-HUDSON RCI (TFX Medical Ltd., High Wycombe HP12 3ST U.K.), blue arrow indicates the mouthpiece, yellow arrow indicates the filter, white arrow indicates the residual cup and oxygen connection, red arrow indicates aerosol flow valve; (B) UP-DRAFT II-HUDSON RCI system parts, (C) valve inner design, (D) valve outer design, (E) Respiromed precision nebulizer special medication, Manufacturer: Int’Air Medical, F-01002 BOURG EN BRESSE, blue arrow indicates the mouthpiece, yellow arrow indicates the filter, white arrow indicates inspiratory breath activated valve (the inner structure of this valve is indicated on the upper right of the same figure), red arrow indicates the connection tip for the residual cup and the green arrow indicates the expiratory activated valve (the inner structure is the same as the expiratory valve), (F) Respiromed precision nebulizer special medication, Manufacturer: Int’Air Medical, F-01002 BOURG EN BRESSE parts, (G) facemask, red arrow indicates the connection tip of the residual cup and oxygen supply, yellow arrow indicates the face mask holes. (For interpretation of the references to color in the artwork, the reader is referred to the web version of the article.)
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(6 l/min and 35 psi), (b) Maxineb® (6 l/min and 35 psi) and (c) Invacare® (6 l/min and 35 psi) (Zarogoulidis et al., 2013c). Therefore in all our experiments we chose to use the nebulizer Maxineb® (6 l/min and 35 psi). 2.2. Drugs The chemotherapy drugs were the following; (i) Paxene® (Paclitaxel) 30 mg/5 ml Pharmachemie B.V., (ii) Gemzar® 1000 mg 17.5 mg (<1 mmol) sodium in each 1000 mg vial, (iii) Cisplatin/Hospira® 100 mg/ml ONCO-TAINTM , (iv) Carboplatin® 10 mg/1 ml VIANEX S.A, (v) Taxotere® (Docetaxel) 80 mg/2 ml and Diluent for Taxotere 80 mg. We gave to the chemotherapy drugs for simplicity in our statistical analysis the following names: cisplatin, carboplatin, paclitaxel, docetaxel and gemcitabine. The drugs cisplatin and carboplatin were used as they were in their vial. The drugs paclitaxel and docetaxel were diluted with 20 ml of NaCl 0.9%. In specific 1 vial of paclitaxel or docetaxel was mixed with 20 ml of NaCl 0.9% and vortexed for 15 min until the solution was homogenous. We wanted to replicate the same solution as in our previous experiment. These drugs in specific after the aerosol administration smeared the glasses of the Malvern® 2000 equipment. In any case a thorough cleaning of the chamber was necessary after every administration even with this dilution. The gemcitabine powder was also diluted with 20 ml of NaCl 0/9%, the mixture was vortexed again for 15 min and a homogenous solution was finally produced (Zarogoulidis et al., 2013d). Several repetitions of the experiments were necessary. The following five antibiotics were used in our previous work: (a) Maxipime® (Cefepime) 2gr. Bristol-Myers Squibb, (b) Begalin – P® (Sulbactam 1gr/Ampicillin 2gr), (d) 3gr Meropenem® (Meropenem) 500 mg, 1gr ANFARM, (c) Zobactam® (Piperacilin 4gr/Tazobactam 0,5 mg) 4,5 g VOCATE., (e) Solvetan® (Ceftazidime) 1gr GSK. The drugs were in dry powder formulation and were diluted with 20 ml NaCl 0.9% in a 50 ml glass container. Again a thorough cleaning of the chamber was necessary after every administration even with this dilution (Zarogoulidis et al., 2013c). Based on our previous experiments we identified the “ideal” combinations in order to produce the finest mist. However; there where cases where 2 different residual-cups offered the finest mist production in the antibiotics group. No difference was observed between the jet-nebulizers. We used only one combination as follows: (a) Zobactam® residual-cup C (6 ml loading) and jetnebulizer Maxineb® , (b) Solvetan® residual-cup G (8 ml loading) and jet-nebulizer Maxineb, (c) Begalin® residual-cup C (6 ml loading) and jet-nebulizer Maxineb® , (d) Meronem® residual-cup C (6 ml loading) and jet-nebulizer Maxineb® , (e) Maxipine® residualcup C (6 ml loading) and jet-nebulizer Maxineb® . Regarding the chemotherapy agents the best combination for all drugs was identified to be residual-cup D (8 ml loading) and jet-nebulizer Maxineb® .
Fig. 2. Small inlets designs and compartments; Red arrow indicates the side where mouth is fitted, Yellow arrow indicates ports for introduction of wires for the inner inlet design. (For interpretation of the references to color in the artwork, the reader is referred to the web version of the article.)
diameter (MMAD) of the produced droplets from the Maxineb® (6 l/min and 35 psi) jet nebulizer. We used the “ideal” combination (residual cup, loading and jet-nebulizer) for each of the drug used identified from our previous work (described in the previous section) (Zarogoulidis et al., 2013c; Zarogoulidis et al., 2013d). (Figs. 2–4.) 2.4. Method of aerosol droplet determination The determination of the d3.2 mean droplet diameter using a laser light scattering apparatus (Malvern Mastersizer 2000, Malvern, Worcestershire, UK) equipped with a Scirocco dry accessory module (Malvern, Worcestershire, UK). This set-up was modified as for the user to be able to spray directly the produced droplets at the sample cell (at a level vertical to the laser beam). The refractive index used for the droplets was 1.33. Light scattering was preferred over a cascade impactor, as the latter is, by design, limited to the number of discriminated size populations up to the number of its filters. The light scattering set-up used in
2.3. Mouthpiece design Best on previous published designs 18 different mouthpieces were engineered. There were two major groups; (a) large with three compartments (A, B, C) and (b) small with two compartments (A, B). We decided to incorporate four different inner grid designs which we named X, V, Dash and Cross. These structures acted as a “filter” for aerosol that passed through the mouthpiece. These designs are used by many commercial aerosol systems, however; we wanted to elicit the effect of the additional compartments and length of mouthpiece in clinical practice. We investigated how the geometry, size, inner grid designs and number of grids (compartments) affect the produced mass median aerodynamic
Fig. 3. Large inlets designs and compartments; Red arrow indicates the side where mouth is fitted, Yellow arrow indicates ports for introduction of wires for the inner inlet design. (For interpretation of the references to color in the artwork, the reader is referred to the web version of the article.)
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2.5. Statistics In both devices the droplet size (dependent variable) produced by three different factors acting interactively was investigated: Drug with 10 levels Inlet Design with 4 levels 3 compartments per large device 2 compartments per small device Thus a two factor analysis of variance (ANOVA fixed effects) was employed for each device type, drug and compartment levels and furthermore drug and inlet design. The droplet size was transformed to its reciprocal 1/MMAD in order to conform to the normality of data for both devices measured. After transformation, derived means were extracted to bring the values to the conventional scale. Statistically differences between factor levels were checked using the Tukey’s pair-wise comparison of means. Fig. 4. Inner mouthpiece designs (only the first compartment is demonstrated in this figure for simplicity reasons). (A) Cross, (B) X, (C) Dash, (D) V.
3. Results
this work measures the light scattering intensity at a very large number of angles, hence a very large number of droplet populations, leading to droplet size distribution plot of a very large points count and this is the reason why light scattering was preferred over other methods. In addition, light scattering as a measurement method is non-invasive to the particles, and being measured. Several repetitions were performed by the team in order to evaluate this technique. (Fig. 5.) We continued using this low concentration of NaCl 0.9% (only 20 ml and without any use of filter) as we wanted to simulate a future mode of administration where a patient would have a fast treatment administration. This can only be pursued when the volume of the drug is low ≤ 20 ml, otherwise the time of administration is very extended. The medical staff that performed the measurements had a protective mask on during the aerosolization (TY 0839V FFP 3, EN 149:2001) (Mansour and Smaldone, 2013).
The number of compartments in the two devices regarding the 10 drugs was found not statistically significant (p-values 0.768 and 0.532 respectively). Therefore another two factor ANOVA was conducted included drug and design this time. For both mouthpiece, drug was the most important factor due the high F-values (Flarge = 251.7, p < 0.001 and Fsmall = 60.1, p < 0.001) produced by the test. Table 1 shows the pattern of drug mean changes. It appears that for the large device the pattern is more clear showing a distinct ranked mean difference among PACLITAXEL, GEMCITABINE and CISPLATIN. Next come three drugs with higher and equal mean values (ZOBACTAM, DOCETATEL, CARBOPLATIN) two drugs with even higher but equal mean values (MERONEM, BAGALIN) and finally two drugs with maximum mean droplet size (SOLVETAN, MAXIPINE). Obviously, PACLITAXEL produces the lowest and most desirable droplet size (1.501). A uniform ranking pattern exists for the first four drugs in the small device. However, clear mean differences are described only by PACLITAXEL, BAGALIN and MAXIPINE, the other drugs showing
Fig. 5. Figure from Department of Food Technology, School of Food Technology and Nutrition, Alexander Technological Educational Institute, Thessaloniki, Greece. Demonstrates the Mastersizer® 2000 and the three Jet-Nebulizers during aerosol droplet measurement.
P. Zarogoulidis et al. / International Journal of Pharmaceutics 456 (2013) 325–331 Table 1 Grouping information using Tukey method of drug mean comparisons for large and small devices. Means that do not share a letter are significantly different. Large inlet DRUG
N
Mean
Grouping
PACLITAXEL GEMCITABINE CISPLATIN ZOBACTAM DOCETAXEL CARBOPLATIN MERONEM BAGALIN SOLVETAN MAXIPINE
12 12 12 11 12 12 12 12 12 12
1.501 1.709 1.908 2.211 2.409 2.431 2.852 3.202 3,987 4.181
A
DRUG
N
Mean
Grouping
PACLITAXEL GEMCITABINE CISPLATIN ZOBACTAM SOLVETAN CARBOPLATIN DOCETAXEL MERONAM BAGALIN MAXIPINE
8 8 8 8 8 8 8 8 8 8
1.572 1.851 2.095 2.151 2.317 2.413 2.625 2.713 3.517 6.398
A
B C D D D E E F F
Small inlet
B B B
C C C C
D D D D E F
overlapping mean values. Again the same drug, PACLITAXEL, comes first with mean value a little higher than that for large device (1.572 > 1.501) and MAXIPINE produces the highest values (6.398 and 4.181) for both devices. The design affected the droplet size but only for large mouthpiece (Flarge = 5.99, p = 0.001, Fsmall = 1.72, p = 0.178). Cross designs create the smallest droplets (2.271) so differing from the other designs whose mean droplets were greater and equal ranging between 2.39 and 2.447 (Table 2). Interaction effects between drugs and design were statistically significant for both devices (Flarge = 8.87, p < 0.001, Fsmall = 5.33, p < 0.001). In both cases the combination PACLITAXELxCross (Table 1 Sup.) was the most beneficial for producing small droplet sizes since the mean values were too low: 1.407 (large) and 1.525 (small). These mean interactive values are smaller than the corresponding ones for the drug PACLITAXEL for both devices so stressing the superiority of that combination. 4. Discussion The factors affecting the aerosol production from jet-nebulizers have been previously identified; (i) salts of the chemical compound (Davis and Bubb, 1978), (ii) design of the residual cup (Clay et al., 1983; Smith et al., 1995; Zarogoulidis et al., 2013c; Zarogoulidis et al., 2013d), (iii) residual cup initial filling (Kendrick et al., 1995), (iv) flow rate (nebulizer capability) (Kendrick et al., 1997), (v) tapping of the nebulizer chamber during nebulization (Kendrick et al., 1997) and (vi) tension-viscosity and drug concentration (Newman et al., 1985). The higher the flow rate and volume in the residual Table 2 Grouping information using Tukey method of design mean comparisons for large devices. Means that do not share a letter are significantly different. DESIGN
N
Mean
Grouping
Cross V X Dash
30 29 30 30
2.271 2.390 2.407 2.447
A B B B
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cup, the smaller the mass median aerodynamic diameter (Clay et al., 1983). The factors affecting the deposition are summarized to: (i) MMAD < 5 m and (ii) humidity and temperature in the airways, since these factors are known to increase the droplet size (Labiris and Dolovich, 2003a). The time of nebulisation is another factor that is not usually included in several experimental therapies upon evaluation (Kendrick et al., 1995; Smith et al., 1995). However; this is also a key parameter to for efficiency and superiority of a new therapy. In the case of inhaled insulin additional aerosol production systems were designed to deliver the drug formulation in short time (Zarogoulidis et al., 2011). Our team identified the “delivery system” as the intermediate stage between production of aerosol and deposition. The face masks and mouthpieces are the two major equipment used, each one with its advantages and disadvantages. The face mask does not need breath synchronization and it can provide the mist of drug to the mouth and nose. It can be used by patients in distress, or in normal status. However; the main disadvantage is the leaking aerosol to the eyes and face skin. The deposition of the drug concentration has been found to be approximately the same to that of the lung on the skin surface (Sangwan et al., 2004). Moreover, depending on the drug several adverse effects could be observed to the eyes (e.g. corticosteroids) or skin (e.g. rash (Mayercik et al., 2011). The face mask design has been found to influence the produced MMAD. In specific the fish mask was observed to have higher inhaled mass than the standard mask or dragon mask at least for albuterol (Lin et al., 2007b). The face mask aerosol administration has been found also to be responsible for influenza particle dispersion. In specific it was presented that the medical personal has to be at least 0.8 m away from hospitilised patients with influenza or suspicious of infectious disease (Hui et al., 2009). Mouthpiece designs have been previously examined to investigate differences between males and females for inhaled insoulin (Boyd et al., 2004). However; no differences were found. There are currently several mouthpiece designs with and without valves. Theoretically mouthpieces with valves (inspiratory and expiratory activated) can control more efficient the drug inhalation pattern and no aerosol is wasted to the environment. There are also several designs were a filter absorbs the aerosol that is exhaled from the mouth and therefore we can measure the concentration that is not inhaled. (Fig. 1.) Previous studies have presented a model where different breathing patterns were used and a filter which was added between the mouthpiece and breathing simulator was used to measure the administered aerosol (Berg and Picard, 2009). This study presented an evaluation system for jet-nebulizers for home care treatment. In the study by Nikander et. al. (Nikander et al., 2000) it was presented that breath synchronization administration using mouthpieces with valves was more efficient than constant aerosol administration with mouthpiece without valves or face mask. In the study by Silkstone et. al. (Silkstone et al., 2002) it was presented that the addition of a spacer to a metered dose inhaler delivers up to five times more drug concentration to the lungs than conventional jet-nebulizer administration. Moreover; it has been previously observed that the mouthpiece geometry affects the amount of throat deposition by controlling the axial component of the exit air flow velocity (Coates et al., 2007). Regarding the mechanically ventilated patients or non-invasive mechanically ventilated the major factors affecting the deposition is the inspiratory flow rate, the flow rate (we need high flow rate), tidal volume, respiratory rate and aerosol production generator (Ari et al., 2010; Everard et al., 1992; Harris et al., 2007). A high flow rate was used to produce and deliver efficiently aerosol iloprost in mechanically ventilated patients (Harris et al., 2007). Computational fluid dynamics display can be used to evaluate future mouthpiece designs and deposition in the respiratory system (Smits and Desmet, 2013). The drift flux model displays the aerosol flow dynamics in the upper
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tracheobronchial airways and can be used to simulate the transport and deposition of submicrometer respiratory aerosols (Xi and Longest, 2008). The different inner mouthpiece designs affect the MMAD of the larger droplets produced. The different grid designs present different patterns of droplet impaction upon them. The major findings were that the cross design produces the smallest droplets only for large mouthpiece with one compartment. This observation can be explained by the higher velocity, turbulence and spin that a droplet obtains inside the larger mouthpiece. At the end of the tube the droplet hits the grid structure with high force and breaks into smaller size droplets. The several compartments (number of grids) > 2 act as “net” after some time of continuous aerosol production which was not identified in the current work. In specific drops of the aerosolized drug can be observed on the different inner grids when > 2 compartments are used. Therefore one compartment at the point of the mouth-mouthpiece connection was observed to be more efficient in producing smaller droplets. In addition, another very important observation was the influence of the solution (drug powder/saline) to the produced aerosol, as it has been previously observed with dry powder (Heng et al., 2013; Park et al., 2013). In our study the antibiotics in specific they were in powder and were diluted in 20 ml of NaCl 0.9%. However; the 20 ml were not sufficient for all antibiotics, therefore we had to reproduce our experiments several times until the smallest possible MMAD was obtain for each one. We have to state that we wanted to have a small volume of solution with high concentration simulating a future antibiotic drug, where the nebulisation time would be short and the minimum inhibitory concentration (MIC50 ) efficient delivered. It is our belief that our results were affected by the large particles within the solutions of the antibiotics (a filter was never used to clear these particles). In any case further development in drug design is needed since the airways have different transporters while descending from the upper to the lower airways (Bosquillon, 2010). Future development of aerosol deposition enhancement should focus not only in the investigation of novel mouthpiece designs but also in production systems and modification of aerosolized particles. Regarding Jet-Nebulizer systems we would like to have as future concept molecules that are produced with high velocity, however; light enough to change trajectory within their route from the mouthpiece to the alveoli. Dry powder inhaler administration could be further enhanced by novel inner designs, however; further experimentation is needed. Identifying which patient is fit (respiratory capability, condition) for each device should be the first step for future experimentation. Moreover, as previously described the defense mechanisms and environment of the airways need novel molecules to be designed in order to bypass them (Labiris and Dolovich, 2003b). Finally, we should choose to use in the clinical practice face masks or mouthpiece designs based on the need of the patient and intended treatment. Conflict of interest None to declare. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j. ijpharm.2013.09.004. References Ari, A., Atalay, O.T., Harwood, R., Sheard, M.M., Aljamhan, E.A., Fink, J.B., 2010. Influence of nebulizer type, position, and bias flow on aerosol drug delivery
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Contents lists available at ScienceDirect
International Journal of Pharmaceutics journal homepage: www.elsevier.com/locate/ijpharm
Personalised medicine
Internal mouthpiece designs as a future perspective for enhanced aerosol deposition. Comparative results for aerosol chemotherapy and aerosol antibiotics Paul Zarogoulidis a,b,∗ , Dimitris Petridis c , Christos Ritzoulis c , Kaid Darwiche b , Ioannis Kioumis a , Konstantinos Porpodis a , Dionysios Spyratos a , Wolfgang Hohenforst-Schmidt d , Lonny Yarmus e , Haidong Huang f , Qiang Li f , Lutz Freitag b , Konstantinos Zarogoulidis a a
Pulmonary Department-Oncology Unit, “G. Papanikolaou” General Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece Department of Interventional Pneumology, Ruhrlandklinik, West German Lung Center, University Hospital, University Duisburg-Essen, Essen, Germany Department of Food Technology, School of Food Technology and Nutrition, Alexander Technological Educational Institute, Thessaloniki, Greece d II Medical Department, “Coburg” Regional Clinic, University of Wuerzburg, Coburg, Germany e Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, USA f Department of Respiratory Diseases Shanghai Hospital, II Military University Hospital, Shanghai, China b c
a r t i c l e
i n f o
Article history: Received 17 August 2013 Received in revised form 3 September 2013 Accepted 5 September 2013 Available online 11 September 2013 Chemical compounds studied in this article: Aztreonam (PubChem CID: 5742832) Gentamycin (PubChem CID: 3467) Tobramycin (PubChem CID: 36294) Ciprofloxacin (PubChem CID: 2764) Cisplatin (PubChem CID: 84093) Carboplatin (PubChem CID: 10339178) Paclitaxel (PubChem CID: 36314) Docetaxel (PubChem CID: 148124) Gemcitabine (PubChem CID: 60750) Doxorubicin (PubChem CID: 31703)
a b s t r a c t Background: In an effort to identify factors producing a finest mist from Jet-Nebulizers we designed 2 mouthpieces with 4 different internal designs and 1–3 compartments. Materials and methods: Ten different drugs previous used with their “ideal” combination of jet-nebulizer, residual-cup and loading were used. For each drug the mass median aerodynamic diameter size had been established along with their “ideal” combination. Results: For both mouthpiece, drug was the most important factor due the high F-values (Flarge = 251.7, p < 0.001 and Fsmall = 60.1, p < 0.001) produced. The design affected the droplet size but only for large mouthpiece (Flarge = 5.99, p = 0.001, Fsmall = 1.72, p = 0.178). Cross designs create the smallest droplets (2.271) so differing from the other designs whose mean droplets were greater and equal ranging between 2.39 and 2.447. The number of compartments in the two devices regarding the 10 drugs was found not statistically significant (p-values 0.768 and 0.532 respectively). Interaction effects between drugs and design were statistically significant for both devices (Flarge = 8.87, p < 0.001, Fsmall = 5.33, p < 0.001). Conclusion: Based on our experiment we conclude that further improvement of the drugs intended for aerosol production is needed. In addition, the mouthpiece design and size play an important role in further enhancing the fine mist production and therefore further experimentation is needed. © 2013 Elsevier B.V. All rights reserved.
Keywords: Aerosol Mouthpiece Designs
1. Introduction Currently the main mode of administration for several therapies is the intravenous route. In the previous years an effort was
∗ Corresponding author at: “G. Papanikolaou” General Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece. Tel.: +49 15779211742; fax: +30 2130992433. E-mail addresses: [email protected], [email protected] (P. Zarogoulidis). 0378-5173/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ijpharm.2013.09.004
made to explore alternative routes of administration in order to enhance the efficiency of therapy and to minimize adverse effects. As it has been observed with several drugs, the adverse effects are directly related to the concentration administered (Miura et al., 2013). In several diseases the target lesion is located to a site which is difficult to approach directly and administer the optimal treatment. Therefore intravenous administration is administered in almost every disease. However; higher concentrations have to be delivered in older to have the desired result. In addition, the discomfort and adverse effects from the intravenous administration is another factor reducing the quality of life of patients (Baron et al.,
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2013; Wynne et al., 2013). The inhaled insulin was one of the first examples where a systematic therapy was redesigned to be administered as aerosol (Zarogoulidis et al., 2011). Inhaled antibiotics followed for patients with cystic fibrosis and patients admitted in the intensive care unit (Geller et al., 2007). Currently experimentation for lung cancer treatment is ongoing as local treatment in the form of intratumoral administration (endobronchial lesions) (Hohenforst-Schmidt et al., 2013), aerosol chemotherapy administration (Zarogoulidis et al., 2012a; Zarogoulidis et al., 2012b) and inhaled gene therapy (Zarogouldis et al., 2012; Zarogoulidis et al., 2013a; Zarogoulidis et al., 2012c). The safety of these novel treatment modalities is under investigation and currently several aerosol production systems are being developed (Darwiche et al., 2013; Zarogoulidis et al., 2013b; Zarogoulidis et al., 2013d). The main concept is to produce treatment administration modalities that are both effective and safe. In our previous work we divided the aerosol production methodology in two clusters: (i) the production system and (ii) the delivery system. We included in the production system the following parameters: (a) jet-nebulizer, (b) residual-cup design, (c) loading of residual-cup and (d) drug. We investigated the interaction of these four parameters between them to identify in what degree one affected the other. We identified for five chemotherapy drugs and five antibiotic drugs the “ideal” combination of these parameters producing the smallest droplets (mass median aerodynamic diameter < 5 m). In our current work we investigated the “delivery system” which is the connection between the residual-cup and upper airways. There are two “delivery systems” that are used nowadays; (a) face mask and (b) mouthpiece. (Fig. 1.) Each one has its advantages and disadvantages which will be analyzed in the discussion section (Lin et al., 2007b; Sangwan et al., 2004). In specific eighteen different mouthpieces were designed in order to evaluate whether this part of the aerosol delivery process affects the mist production and hence the performance. It has been previous investigated that factors such as; turbulence, inlet size, air flow, mouthpiece and
grid affect the production of the aerosol mist (Jiang et al., 2012). Inhaled insulin is an example again where different mouthpiece designs were investigated in an effort to enhance the aerosol production. Indeed the mouthpiece design was observed to be a key factor affecting the mist production at least for inhaled insulin (Boyd et al., 2004; Coates et al., 2007). The addition of a spacer has presented again favorable results when connected to a metered dose inhaler or jet-nebulizer production system (Silkstone et al., 2002). A third system identified to further influence the deposition of aerosol mist consists of the following geometrical factors; geometrical; mouth, oropharynx, larynx intra-thoracic airways up to six generations. The intra-thoracic airways however; is not a stable systems since the diameter changes due to underlying conditions (e.g. bronchoconstriction, excessive mucus production, viscosity of mucus) and diseases (e.g. chronic obstructive pulmonary disease, cystic fibrosis, asthma) (Lin et al., 2007a). The breathing pattern plays also an important role of aerosol deposition (Foust et al., 1991; Nikander et al., 2000). We will present our results and indicate future investigational directions towards the aerosol production methodology. 2. Materials and methods 2.1. Nebulizers Based on our previous experiments we identified that for chemotherapy drugs (Cisplatin, Paclitaxel, Docetaxel, Gemcitabine and Carboplatin) the “ideal” combination producing the smallest droplets (mass median aerodynamic diameter) was the nebulizer Maxineb® (6 l/min and 35 psi), residual cup D with 8 ml loading (Zarogoulidis et al., 2013d). Regarding the antibiotics the “ideal” combination was for zobactam the residual cup C and G with 6 ml loading, for solvetan residual cup D with 8 ml loading and for maxipine, begalin, meronem residual cup C with 6 ml loading. There was no difference observed between the nebulisers (a) Sunmist®
Fig. 1. (A) ISO-NEB® Filtered Nebulizer System, UP-DRAFT II-HUDSON RCI (TFX Medical Ltd., High Wycombe HP12 3ST U.K.), blue arrow indicates the mouthpiece, yellow arrow indicates the filter, white arrow indicates the residual cup and oxygen connection, red arrow indicates aerosol flow valve; (B) UP-DRAFT II-HUDSON RCI system parts, (C) valve inner design, (D) valve outer design, (E) Respiromed precision nebulizer special medication, Manufacturer: Int’Air Medical, F-01002 BOURG EN BRESSE, blue arrow indicates the mouthpiece, yellow arrow indicates the filter, white arrow indicates inspiratory breath activated valve (the inner structure of this valve is indicated on the upper right of the same figure), red arrow indicates the connection tip for the residual cup and the green arrow indicates the expiratory activated valve (the inner structure is the same as the expiratory valve), (F) Respiromed precision nebulizer special medication, Manufacturer: Int’Air Medical, F-01002 BOURG EN BRESSE parts, (G) facemask, red arrow indicates the connection tip of the residual cup and oxygen supply, yellow arrow indicates the face mask holes. (For interpretation of the references to color in the artwork, the reader is referred to the web version of the article.)
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(6 l/min and 35 psi), (b) Maxineb® (6 l/min and 35 psi) and (c) Invacare® (6 l/min and 35 psi) (Zarogoulidis et al., 2013c). Therefore in all our experiments we chose to use the nebulizer Maxineb® (6 l/min and 35 psi). 2.2. Drugs The chemotherapy drugs were the following; (i) Paxene® (Paclitaxel) 30 mg/5 ml Pharmachemie B.V., (ii) Gemzar® 1000 mg 17.5 mg (<1 mmol) sodium in each 1000 mg vial, (iii) Cisplatin/Hospira® 100 mg/ml ONCO-TAINTM , (iv) Carboplatin® 10 mg/1 ml VIANEX S.A, (v) Taxotere® (Docetaxel) 80 mg/2 ml and Diluent for Taxotere 80 mg. We gave to the chemotherapy drugs for simplicity in our statistical analysis the following names: cisplatin, carboplatin, paclitaxel, docetaxel and gemcitabine. The drugs cisplatin and carboplatin were used as they were in their vial. The drugs paclitaxel and docetaxel were diluted with 20 ml of NaCl 0.9%. In specific 1 vial of paclitaxel or docetaxel was mixed with 20 ml of NaCl 0.9% and vortexed for 15 min until the solution was homogenous. We wanted to replicate the same solution as in our previous experiment. These drugs in specific after the aerosol administration smeared the glasses of the Malvern® 2000 equipment. In any case a thorough cleaning of the chamber was necessary after every administration even with this dilution. The gemcitabine powder was also diluted with 20 ml of NaCl 0/9%, the mixture was vortexed again for 15 min and a homogenous solution was finally produced (Zarogoulidis et al., 2013d). Several repetitions of the experiments were necessary. The following five antibiotics were used in our previous work: (a) Maxipime® (Cefepime) 2gr. Bristol-Myers Squibb, (b) Begalin – P® (Sulbactam 1gr/Ampicillin 2gr), (d) 3gr Meropenem® (Meropenem) 500 mg, 1gr ANFARM, (c) Zobactam® (Piperacilin 4gr/Tazobactam 0,5 mg) 4,5 g VOCATE., (e) Solvetan® (Ceftazidime) 1gr GSK. The drugs were in dry powder formulation and were diluted with 20 ml NaCl 0.9% in a 50 ml glass container. Again a thorough cleaning of the chamber was necessary after every administration even with this dilution (Zarogoulidis et al., 2013c). Based on our previous experiments we identified the “ideal” combinations in order to produce the finest mist. However; there where cases where 2 different residual-cups offered the finest mist production in the antibiotics group. No difference was observed between the jet-nebulizers. We used only one combination as follows: (a) Zobactam® residual-cup C (6 ml loading) and jetnebulizer Maxineb® , (b) Solvetan® residual-cup G (8 ml loading) and jet-nebulizer Maxineb, (c) Begalin® residual-cup C (6 ml loading) and jet-nebulizer Maxineb® , (d) Meronem® residual-cup C (6 ml loading) and jet-nebulizer Maxineb® , (e) Maxipine® residualcup C (6 ml loading) and jet-nebulizer Maxineb® . Regarding the chemotherapy agents the best combination for all drugs was identified to be residual-cup D (8 ml loading) and jet-nebulizer Maxineb® .
Fig. 2. Small inlets designs and compartments; Red arrow indicates the side where mouth is fitted, Yellow arrow indicates ports for introduction of wires for the inner inlet design. (For interpretation of the references to color in the artwork, the reader is referred to the web version of the article.)
diameter (MMAD) of the produced droplets from the Maxineb® (6 l/min and 35 psi) jet nebulizer. We used the “ideal” combination (residual cup, loading and jet-nebulizer) for each of the drug used identified from our previous work (described in the previous section) (Zarogoulidis et al., 2013c; Zarogoulidis et al., 2013d). (Figs. 2–4.) 2.4. Method of aerosol droplet determination The determination of the d3.2 mean droplet diameter using a laser light scattering apparatus (Malvern Mastersizer 2000, Malvern, Worcestershire, UK) equipped with a Scirocco dry accessory module (Malvern, Worcestershire, UK). This set-up was modified as for the user to be able to spray directly the produced droplets at the sample cell (at a level vertical to the laser beam). The refractive index used for the droplets was 1.33. Light scattering was preferred over a cascade impactor, as the latter is, by design, limited to the number of discriminated size populations up to the number of its filters. The light scattering set-up used in
2.3. Mouthpiece design Best on previous published designs 18 different mouthpieces were engineered. There were two major groups; (a) large with three compartments (A, B, C) and (b) small with two compartments (A, B). We decided to incorporate four different inner grid designs which we named X, V, Dash and Cross. These structures acted as a “filter” for aerosol that passed through the mouthpiece. These designs are used by many commercial aerosol systems, however; we wanted to elicit the effect of the additional compartments and length of mouthpiece in clinical practice. We investigated how the geometry, size, inner grid designs and number of grids (compartments) affect the produced mass median aerodynamic
Fig. 3. Large inlets designs and compartments; Red arrow indicates the side where mouth is fitted, Yellow arrow indicates ports for introduction of wires for the inner inlet design. (For interpretation of the references to color in the artwork, the reader is referred to the web version of the article.)
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2.5. Statistics In both devices the droplet size (dependent variable) produced by three different factors acting interactively was investigated: Drug with 10 levels Inlet Design with 4 levels 3 compartments per large device 2 compartments per small device Thus a two factor analysis of variance (ANOVA fixed effects) was employed for each device type, drug and compartment levels and furthermore drug and inlet design. The droplet size was transformed to its reciprocal 1/MMAD in order to conform to the normality of data for both devices measured. After transformation, derived means were extracted to bring the values to the conventional scale. Statistically differences between factor levels were checked using the Tukey’s pair-wise comparison of means. Fig. 4. Inner mouthpiece designs (only the first compartment is demonstrated in this figure for simplicity reasons). (A) Cross, (B) X, (C) Dash, (D) V.
3. Results
this work measures the light scattering intensity at a very large number of angles, hence a very large number of droplet populations, leading to droplet size distribution plot of a very large points count and this is the reason why light scattering was preferred over other methods. In addition, light scattering as a measurement method is non-invasive to the particles, and being measured. Several repetitions were performed by the team in order to evaluate this technique. (Fig. 5.) We continued using this low concentration of NaCl 0.9% (only 20 ml and without any use of filter) as we wanted to simulate a future mode of administration where a patient would have a fast treatment administration. This can only be pursued when the volume of the drug is low ≤ 20 ml, otherwise the time of administration is very extended. The medical staff that performed the measurements had a protective mask on during the aerosolization (TY 0839V FFP 3, EN 149:2001) (Mansour and Smaldone, 2013).
The number of compartments in the two devices regarding the 10 drugs was found not statistically significant (p-values 0.768 and 0.532 respectively). Therefore another two factor ANOVA was conducted included drug and design this time. For both mouthpiece, drug was the most important factor due the high F-values (Flarge = 251.7, p < 0.001 and Fsmall = 60.1, p < 0.001) produced by the test. Table 1 shows the pattern of drug mean changes. It appears that for the large device the pattern is more clear showing a distinct ranked mean difference among PACLITAXEL, GEMCITABINE and CISPLATIN. Next come three drugs with higher and equal mean values (ZOBACTAM, DOCETATEL, CARBOPLATIN) two drugs with even higher but equal mean values (MERONEM, BAGALIN) and finally two drugs with maximum mean droplet size (SOLVETAN, MAXIPINE). Obviously, PACLITAXEL produces the lowest and most desirable droplet size (1.501). A uniform ranking pattern exists for the first four drugs in the small device. However, clear mean differences are described only by PACLITAXEL, BAGALIN and MAXIPINE, the other drugs showing
Fig. 5. Figure from Department of Food Technology, School of Food Technology and Nutrition, Alexander Technological Educational Institute, Thessaloniki, Greece. Demonstrates the Mastersizer® 2000 and the three Jet-Nebulizers during aerosol droplet measurement.
P. Zarogoulidis et al. / International Journal of Pharmaceutics 456 (2013) 325–331 Table 1 Grouping information using Tukey method of drug mean comparisons for large and small devices. Means that do not share a letter are significantly different. Large inlet DRUG
N
Mean
Grouping
PACLITAXEL GEMCITABINE CISPLATIN ZOBACTAM DOCETAXEL CARBOPLATIN MERONEM BAGALIN SOLVETAN MAXIPINE
12 12 12 11 12 12 12 12 12 12
1.501 1.709 1.908 2.211 2.409 2.431 2.852 3.202 3,987 4.181
A
DRUG
N
Mean
Grouping
PACLITAXEL GEMCITABINE CISPLATIN ZOBACTAM SOLVETAN CARBOPLATIN DOCETAXEL MERONAM BAGALIN MAXIPINE
8 8 8 8 8 8 8 8 8 8
1.572 1.851 2.095 2.151 2.317 2.413 2.625 2.713 3.517 6.398
A
B C D D D E E F F
Small inlet
B B B
C C C C
D D D D E F
overlapping mean values. Again the same drug, PACLITAXEL, comes first with mean value a little higher than that for large device (1.572 > 1.501) and MAXIPINE produces the highest values (6.398 and 4.181) for both devices. The design affected the droplet size but only for large mouthpiece (Flarge = 5.99, p = 0.001, Fsmall = 1.72, p = 0.178). Cross designs create the smallest droplets (2.271) so differing from the other designs whose mean droplets were greater and equal ranging between 2.39 and 2.447 (Table 2). Interaction effects between drugs and design were statistically significant for both devices (Flarge = 8.87, p < 0.001, Fsmall = 5.33, p < 0.001). In both cases the combination PACLITAXELxCross (Table 1 Sup.) was the most beneficial for producing small droplet sizes since the mean values were too low: 1.407 (large) and 1.525 (small). These mean interactive values are smaller than the corresponding ones for the drug PACLITAXEL for both devices so stressing the superiority of that combination. 4. Discussion The factors affecting the aerosol production from jet-nebulizers have been previously identified; (i) salts of the chemical compound (Davis and Bubb, 1978), (ii) design of the residual cup (Clay et al., 1983; Smith et al., 1995; Zarogoulidis et al., 2013c; Zarogoulidis et al., 2013d), (iii) residual cup initial filling (Kendrick et al., 1995), (iv) flow rate (nebulizer capability) (Kendrick et al., 1997), (v) tapping of the nebulizer chamber during nebulization (Kendrick et al., 1997) and (vi) tension-viscosity and drug concentration (Newman et al., 1985). The higher the flow rate and volume in the residual Table 2 Grouping information using Tukey method of design mean comparisons for large devices. Means that do not share a letter are significantly different. DESIGN
N
Mean
Grouping
Cross V X Dash
30 29 30 30
2.271 2.390 2.407 2.447
A B B B
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cup, the smaller the mass median aerodynamic diameter (Clay et al., 1983). The factors affecting the deposition are summarized to: (i) MMAD < 5 m and (ii) humidity and temperature in the airways, since these factors are known to increase the droplet size (Labiris and Dolovich, 2003a). The time of nebulisation is another factor that is not usually included in several experimental therapies upon evaluation (Kendrick et al., 1995; Smith et al., 1995). However; this is also a key parameter to for efficiency and superiority of a new therapy. In the case of inhaled insulin additional aerosol production systems were designed to deliver the drug formulation in short time (Zarogoulidis et al., 2011). Our team identified the “delivery system” as the intermediate stage between production of aerosol and deposition. The face masks and mouthpieces are the two major equipment used, each one with its advantages and disadvantages. The face mask does not need breath synchronization and it can provide the mist of drug to the mouth and nose. It can be used by patients in distress, or in normal status. However; the main disadvantage is the leaking aerosol to the eyes and face skin. The deposition of the drug concentration has been found to be approximately the same to that of the lung on the skin surface (Sangwan et al., 2004). Moreover, depending on the drug several adverse effects could be observed to the eyes (e.g. corticosteroids) or skin (e.g. rash (Mayercik et al., 2011). The face mask design has been found to influence the produced MMAD. In specific the fish mask was observed to have higher inhaled mass than the standard mask or dragon mask at least for albuterol (Lin et al., 2007b). The face mask aerosol administration has been found also to be responsible for influenza particle dispersion. In specific it was presented that the medical personal has to be at least 0.8 m away from hospitilised patients with influenza or suspicious of infectious disease (Hui et al., 2009). Mouthpiece designs have been previously examined to investigate differences between males and females for inhaled insoulin (Boyd et al., 2004). However; no differences were found. There are currently several mouthpiece designs with and without valves. Theoretically mouthpieces with valves (inspiratory and expiratory activated) can control more efficient the drug inhalation pattern and no aerosol is wasted to the environment. There are also several designs were a filter absorbs the aerosol that is exhaled from the mouth and therefore we can measure the concentration that is not inhaled. (Fig. 1.) Previous studies have presented a model where different breathing patterns were used and a filter which was added between the mouthpiece and breathing simulator was used to measure the administered aerosol (Berg and Picard, 2009). This study presented an evaluation system for jet-nebulizers for home care treatment. In the study by Nikander et. al. (Nikander et al., 2000) it was presented that breath synchronization administration using mouthpieces with valves was more efficient than constant aerosol administration with mouthpiece without valves or face mask. In the study by Silkstone et. al. (Silkstone et al., 2002) it was presented that the addition of a spacer to a metered dose inhaler delivers up to five times more drug concentration to the lungs than conventional jet-nebulizer administration. Moreover; it has been previously observed that the mouthpiece geometry affects the amount of throat deposition by controlling the axial component of the exit air flow velocity (Coates et al., 2007). Regarding the mechanically ventilated patients or non-invasive mechanically ventilated the major factors affecting the deposition is the inspiratory flow rate, the flow rate (we need high flow rate), tidal volume, respiratory rate and aerosol production generator (Ari et al., 2010; Everard et al., 1992; Harris et al., 2007). A high flow rate was used to produce and deliver efficiently aerosol iloprost in mechanically ventilated patients (Harris et al., 2007). Computational fluid dynamics display can be used to evaluate future mouthpiece designs and deposition in the respiratory system (Smits and Desmet, 2013). The drift flux model displays the aerosol flow dynamics in the upper
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tracheobronchial airways and can be used to simulate the transport and deposition of submicrometer respiratory aerosols (Xi and Longest, 2008). The different inner mouthpiece designs affect the MMAD of the larger droplets produced. The different grid designs present different patterns of droplet impaction upon them. The major findings were that the cross design produces the smallest droplets only for large mouthpiece with one compartment. This observation can be explained by the higher velocity, turbulence and spin that a droplet obtains inside the larger mouthpiece. At the end of the tube the droplet hits the grid structure with high force and breaks into smaller size droplets. The several compartments (number of grids) > 2 act as “net” after some time of continuous aerosol production which was not identified in the current work. In specific drops of the aerosolized drug can be observed on the different inner grids when > 2 compartments are used. Therefore one compartment at the point of the mouth-mouthpiece connection was observed to be more efficient in producing smaller droplets. In addition, another very important observation was the influence of the solution (drug powder/saline) to the produced aerosol, as it has been previously observed with dry powder (Heng et al., 2013; Park et al., 2013). In our study the antibiotics in specific they were in powder and were diluted in 20 ml of NaCl 0.9%. However; the 20 ml were not sufficient for all antibiotics, therefore we had to reproduce our experiments several times until the smallest possible MMAD was obtain for each one. We have to state that we wanted to have a small volume of solution with high concentration simulating a future antibiotic drug, where the nebulisation time would be short and the minimum inhibitory concentration (MIC50 ) efficient delivered. It is our belief that our results were affected by the large particles within the solutions of the antibiotics (a filter was never used to clear these particles). In any case further development in drug design is needed since the airways have different transporters while descending from the upper to the lower airways (Bosquillon, 2010). Future development of aerosol deposition enhancement should focus not only in the investigation of novel mouthpiece designs but also in production systems and modification of aerosolized particles. Regarding Jet-Nebulizer systems we would like to have as future concept molecules that are produced with high velocity, however; light enough to change trajectory within their route from the mouthpiece to the alveoli. Dry powder inhaler administration could be further enhanced by novel inner designs, however; further experimentation is needed. Identifying which patient is fit (respiratory capability, condition) for each device should be the first step for future experimentation. Moreover, as previously described the defense mechanisms and environment of the airways need novel molecules to be designed in order to bypass them (Labiris and Dolovich, 2003b). Finally, we should choose to use in the clinical practice face masks or mouthpiece designs based on the need of the patient and intended treatment. Conflict of interest None to declare. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j. ijpharm.2013.09.004. References Ari, A., Atalay, O.T., Harwood, R., Sheard, M.M., Aljamhan, E.A., Fink, J.B., 2010. Influence of nebulizer type, position, and bias flow on aerosol drug delivery
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