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Nasal Tramadol delivery system: A new approach for improved pain therapy
European Journal of Pain Supplements 5 (2011) 449–452
Contents lists available at SciVerse ScienceDirect
European Journal of Pain Supplements journal homepage: www.EuropeanJournalPain.com
Nasal Tramadol delivery system: A new approach for improved pain therapy Shaher Duchi a, Elka Touitou a,⇑, Lorenzo Pradella b, Francesco Marchini b, Denize Ainbinder a a b
Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel Zcube S.r.l., Italy
a r t i c l e
i n f o
Keywords: Tramadol Pain Nasal delivery system Analgesia
a b s t r a c t The present work investigates Tramadol nasal delivery for effective analgesia with a rapid onset of action. The pharmacokinetic and pharmacodynamic behavior of Tramadol, a non-opiate analgesic drug, following its administration to rodents from a nasal delivery system was compared to oral aqueous solution. Following Tramadol nasal administration in animals at a dose of 10 mg/kg, a Cmax value of 2421 ± 651 ng/ml was obtained as compared to a four time lower value after oral delivery (644 ± 349 ng/ml). The high plasma concentration was achieved at 10 min (tmax), indicating a rapid systemic absorption of the drug. Tramadol nasal delivery system treatment in animal Writhing model at a relative low dose of only 5 mg/kg significantly increased the analgesic effect, as compared to the oral administration, both 30 min before and immediately with pain induction. The local safety of Tramadol nasal system was good with no histological or nasal cavity changes. The outcomes of this work are that nasal administration of Tramadol could improve pain therapy and shorten its onset of action. The treatment by the nasal pathway could overcome the side effects associated with parenteral and oral delivery. Furthermore, due to the rapid and efficient delivery of the drug to the blood, nasal administration of Tramadol could be considered for the treatment of breakthrough pain. Ó 2011 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.
1. Introduction One important challenge in pain treatment is the achievement of a short onset of an effective analgesic action (Pinardi et al., 1998; Dursteler et al., 2006). Various strategies have been investigated to improve analgesic drug efficiency. One successful recent approach is the use of the nasal route as a portal for drug delivery. Nasal administration of Fentanyl and Ketorolac tromethamine has been recently approved by the FDA for the treatment of pain. The nasal delivery could enable non-invasive drug self-administration, overcoming the first pass-effect in the liver and increasing drug bioavailability compared to the oral route. Moreover, nasal drug administration provides an attractive needle-free alternative for the currently injectable drugs (Hinchcliffe and Illum, 1999). However, a main limitation of this route of delivery is related to the low doses that could be administered, meaning that in order to achieve efficient treatments, a high absorption of the drug from the nasal cavity is crucial. While some drugs, like Fentanyl, possess
⇑ Corresponding author. Address: Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 91120, Israel. Tel.: +972 2 6758660; fax: +972 2 6757611. E-mail address: [email protected] (E. Touitou).
excellent absorption properties through the nasal mucosa, many other molecules may require the use of appropriate delivery carriers for efficient nasal administration. For such drugs, improving nasal absorption could be a critical request. Tramadol HCl is a cationic hydrophilic molecule, with central analgesic activity. It is a synthetic analogue of codeine that binds to mu-opioid receptor and inhibits norepinephrine and serotonin reuptake (Lewis and Han, 1997). Tramadol is available as drops, capsules and sustained-release formulations for oral use, suppositories for rectal use and solution for intramuscular, intravenous and subcutaneous injection (Grond and Sablotzki, 2004). After oral administration, the drug is rapidly and extensively absorbed and metabolized in the liver. Analgesia begins within 1 h and usually reaches peak blood concentration within 2 h. In patients with moderate postoperative pain, the efficacy of IV or IM administered Tramadol is equal to that of morphine; but by the conventional oral mode of administration it is less effective for severe acute pain (Lewis and Han, 1997). Here, we present results of our investigation on the pharmacokinetic and pharmacodynamic behavior of Tramadol following administration from nasal delivery system as compared to oral aqueous solution. The delivery system was designed to be able to incorporate high concentrations of the drug and is composed of
1754-3207/$36.00 Ó 2011 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.eujps.2011.08.009
450
S. Duchi et al. / European Journal of Pain Supplements 5 (2011) 449–452
FDA approved ingredients for nasal use. The local safety of Tramadol nasal system was also tested.
Table 1 Pharmacokinetic parameters of Tramadol HCl in mice plasma (Mean ± SEM). Tramadol HCl (10 mg/kg) was administered from nasal delivery system or as oral aqueous solution.
2. Results and discussion 2.1. Tramadol levels in plasma following nasal administration in mice
Nasal delivery system
Oral aqueous solution
Cmax tmax AUC0–3h FREL%
2421 ± 651 ng/ml* 10 min 93 ± 4 lg min/ml* 198
644 ± 349 ng/ml 10 min 47 ± 2 lg min/ml
n, 16; for each experimental group. P < 0.05 nasal delivery system vs. oral aqueous solution.
*
F REL % ¼ ½ðAUCIN DOSEPO Þ=½ðAUCPO DOSEIN Þ 100
ð1Þ
These values of AUC and relative bioavailability suggest a highly improved absorption of Tramadol following the nasal delivery. 2.2. Analgesic effect of Tramadol following nasal administration in Writhing mice model The analgesic effect of Tramadol on acute nociception was investigated by using the Writhing test in mice. Tramadol HCl at a relative low drug dose of 5 mg/kg was administered in the nasal delivery system and as oral aqueous solution. The drug administration was made under different regimens: immediately before pain induction or as preventive treatment 30 min before pain induction. Mice in the control group have not received any treatment before pain induction. Immediately and 30 min after the administration, each animal was injected IP with 0.6% v/v acetic acid solution (10 ml/kg) and individually housed in a cage with a smooth flat floor. Anti-nociception was recorded by counting the number of writhes 5 min after the injection of acetic acid, for a period of
A
Oral aqueous solution
45
Control
40 Mean Writhing Episodes
The joint ethics committee (IACUC) of the Hebrew University and Hadassah Medical Center for animal welfare approved all animal study protocols. The Hebrew University is an AAALAC international accredited institute. All animal experiments were conducted in full compliance with the approved protocols. Animals were housed under normal 12-h light/dark cycle and a temperature of 21–22 °C, with food and water freely available. Tramadol HCl at a dose of 10 mg/kg was given to female C57BL/ 6J mice from nasal delivery system and from oral aqueous solution. A total of 32 mice were used; 16 for each experimental group; four mice for each time point. Quantification of Tramadol HCl in plasma samples following liquid–liquid extraction was performed by a modified method described by Gan et al. (2002), using an HPLC apparatus (Hitachi, Japan) equipped with UV variable ultraviolet detector and HSM computerized analysis program. Briefly, Tramadol detection was carried out at 220 nm on an ApolloÒ C18 5u RPC18 (5 lm particles size, 25 cm 4 mm I.D.) column, with a mobile phase containing an Acetonitrile:Phosphate Buffer 0.01 M containing 0.1% v/v Triethylamine, 22:78 v/v, adjusted at pH 3 with Orthophosphoric acid, at a flow-rate of 1 ml/min. Plasma levels of Tramadol plotted in Fig. 1 show that following nasal administration, the blood drug concentration increased rapidly with a peak at 10 min (the first time point sampled) and was much higher for the next 30 min as compared to oral (812 ± 198 and 257 ± 27 ng/ml, respectively). The higher profile was maintained up to 1 h. The pharmacokinetic parameters given in Table 1 indicate that a four time higher Cmax value was obtained by nasal drug administration vs. oral (2421 ± 651 ng/ml vs. 644 ± 349 ng/ml, respectively). This improved Cmax was obtained shortly after the administration, at 10 min (tmax) after the administration, indicating a rapid systemic absorption of the drug. A significantly higher AUC value of 93 ± 4 lg min/ml was calculated for the nasal delivery of Tramadol vs. only 47 ± 2 lg min/ml following oral drug. The relative bioavailability (FREL%) for nasal vs. oral Tramadol administration (calculated by Eq. (1)) was 198%.
Parameters
35 30
Nasal delivery system
25 20
*
15 10 5 0
Nasal delivery system
* 3000
B
Oral aqueous solution
45
Control Oral aqueous solution
40
2500
Mean Writhing Episodes
Tramadol concentration in plasma (ng/ml)
3500
2000 * 1500 1000 500
35 30 25 20
** Nasal delivery system
*
15 10 5
0 0
30
60
90
120
150
180
0
Time (min)
Fig. 1. Mean plasma levels (ng/ml, Mean ± SEM) following Tramadol HCl (10 mg/ kg) administration from: j nasal delivery system or N oral aqueous solution. n, 4; for each time point in each treatment group. ⁄P < 0.05 nasal delivery system vs. oral aqueous solution.
Fig. 2. Tramadol HCl (5 mg/kg) analgesic activity (Mean ± SD, Writhing episodes during 10 min observation) following administration from nasal delivery system or oral aqueous solution, (A) immediately or (B) 30 min before pain induction. n, 7; for each experimental group. ⁄P < 0.05 nasal delivery system vs. all groups, ⁄⁄P < 0.05 oral aqueous solution vs. untreated control group.
S. Duchi et al. / European Journal of Pain Supplements 5 (2011) 449–452
451
Fig. 3. Photomicrographs of nasal cavities excised from mice treated two times a day for 10 days with empty or Tramadol containing nasal delivery system or saline (H&E, 4000).
10 min. A writhe was indicated by abdominal constriction and stretching of at least one hind limb (Pinardi et al., 1998; Dursteler et al., 2006; Collier et al., 1968). The maximum possible effect (MPE%) of the treatments on the Writhing test was expressed as the inhibition percent of the number of writhes in a drug-treated animal, when compared to the mean number of writhes measured in a group of untreated mice (control) according to Eq. (2):
MPE% ¼ ½Mean of writhes in control group —Mean of writhes in treated group =½Mean of writhes in control group 100
ð2Þ
Results given in Fig. 2A show that oral administration of Tramadol at 5 mg/kg immediately before pain induction had no analgesic effect (no reduction in the number of writhes was observed as compared to untreated animals). On the other hand, under the same treatment regimen, Tramadol administration from nasal delivery system resulted in a significant anti-nociceptive activity and a high efficiency in suppressing the pain episodes. The maximum possible effect (MPE) value for this treatment was 67.7%. The analgesic activity of the same drug dose administered 30 min before pain induction from the nasal delivery system and after oral administration were both statistically significant as compared to the control untreated animals. However the nasal drug administration had a statistically significantly higher effect (P < 0.05), as compared to both oral and control animal groups (Fig. 2B). The nasal MPE value was more than twice higher, the values being 67.2% and 32.3% for nasal delivery and oral administration, respectively. From the above results, it can be clearly seen, that even at a low drug dose of 5 mg/kg, the effect measured following drug administration immediately before pain induction was significantly higher for the nasal delivery system as compared to oral administration. Furthermore, the nasal results indicate not only a rapid onset of the effect, but also a higher anti-nociceptive activity over time in comparison to the oral solution. It is noteworthy, that in experiments comparing the analgesic effect of Tramadol nasal delivery system to a nasal aqueous solution at the same dose, the aqueous solution had a much inferior effect at all administration regimens tested (immediately, 30 and 60 min before pain induction). Results of further experiments carried out by us (results not presented here) in larger animals, rat and sheep, sustain the efficient delivery behavior observed in this work. 2.3. Safety of Tramadol nasal delivery system administration In order to evaluate whether the Tramadol delivery system has any damaging effect on the nasal cavity and mucosa, an experiment was carried out in which three systems were nasally administrated to six mice twice a day for 10 days: saline, empty delivery
system carrier and Tramadol delivery system. At the end of the administration period, the animals were sacrificed, decapitated and the nasal cavity was removed. Samples embedded in paraffin, sectioned and stained with Hematoxylin & Eosin (H&E) were observed with a light microscope (Zeiss™, Axioskop 2 plus) for changes in appearance and structure of the nasal cavity and mucosa. Local toxicity was assessed by evaluating the histopathological alterations in the different regions of the nasal cavity (cartilage and turbinate bone, lamina propria and submucosa, mucosal epithelium and lumen). Examination of the nasal cavities excised from treated mice at the end of the experimental period showed mucosa with normal histology (intact and normal epithelium) and no inflammatory cells infiltration. Only limited and minimal non-cellular homogeneous material was observed in the lumen for all treatments (Fig. 3). 3. Conclusions Nasal administration of Tramadol in animals demonstrates that when given in a delivery system by this pathway, the drug systemic absorption could be significantly improved. Results of experiments in animal Writhing model, evaluating the drug antinociceptive effect, indicate that Tramadol nasal delivery system treatment significantly increased the analgesic effect, as compared to oral administration, both 30 min before and immediately with pain induction. The significance of these results is that nasal administration of the drug was able to increase the analgesic effect and provide a rapid onset of action, improving the pain therapy. The local safety of Tramadol nasal system was good with no histological or nasal cavity changes. The findings of this work suggest that treatment with Tramadol nasal delivery system could enhance the efficiency of the drug and shorten its onset of action relative to oral treatment, without damaging the nasal mucosal membrane. Relative to parenteral treatment, the nasal pathway administration could prevent side effects and decrease the need of patient hospitalization. Moreover, due to the rapid and efficient delivery of the drug to the blood, nasal administration of Tramadol could be considered for the treatment of breakthrough pain. 4. Conflict of interest None. References Collier HO, Dinneen LC, Johnson CA, Schneider C. The abdominal constriction response and its suppression by analgesic drugs in the mouse. Br J Pharmacol Chemother 1968;32:295–310. Dursteler C, Mases A, Fernandez V, Pol O, Puig MM. Interaction between tramadol and two anti-emetics on nociception and gastrointestinal transit in mice. Eur J Pain 2006;10:629–38.
452
S. Duchi et al. / European Journal of Pain Supplements 5 (2011) 449–452
Gan SH, Ismail R, Wan Adnan WA, Wan Z. Method development and validation of a high-performance liquid chromatographic method for tramadol in human plasma using liquid–liquid extraction. J Chromatogr B Anal Technol Biomed Life Sci 2002;772:123–9. Grond S, Sablotzki A. Clinical pharmacology of tramadol. Clin Pharmacokinet 2004;43:879–923.
Hinchcliffe M, Illum L. Intranasal insulin delivery and therapy. Adv Drug Deliv Rev 1999;35:199–234. Lewis KS, Han NH. Tramadol: a new centrally acting analgesic. Am J Health Syst Pharm 1997;54:643–52. Pinardi G, Pelissier T, Miranda HF. Interactions in the antinociceptive effect of tramadol in mice: an isobolographic analysis. Eur J Pain 1998;2:343–50.
Contents lists available at SciVerse ScienceDirect
European Journal of Pain Supplements journal homepage: www.EuropeanJournalPain.com
Nasal Tramadol delivery system: A new approach for improved pain therapy Shaher Duchi a, Elka Touitou a,⇑, Lorenzo Pradella b, Francesco Marchini b, Denize Ainbinder a a b
Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel Zcube S.r.l., Italy
a r t i c l e
i n f o
Keywords: Tramadol Pain Nasal delivery system Analgesia
a b s t r a c t The present work investigates Tramadol nasal delivery for effective analgesia with a rapid onset of action. The pharmacokinetic and pharmacodynamic behavior of Tramadol, a non-opiate analgesic drug, following its administration to rodents from a nasal delivery system was compared to oral aqueous solution. Following Tramadol nasal administration in animals at a dose of 10 mg/kg, a Cmax value of 2421 ± 651 ng/ml was obtained as compared to a four time lower value after oral delivery (644 ± 349 ng/ml). The high plasma concentration was achieved at 10 min (tmax), indicating a rapid systemic absorption of the drug. Tramadol nasal delivery system treatment in animal Writhing model at a relative low dose of only 5 mg/kg significantly increased the analgesic effect, as compared to the oral administration, both 30 min before and immediately with pain induction. The local safety of Tramadol nasal system was good with no histological or nasal cavity changes. The outcomes of this work are that nasal administration of Tramadol could improve pain therapy and shorten its onset of action. The treatment by the nasal pathway could overcome the side effects associated with parenteral and oral delivery. Furthermore, due to the rapid and efficient delivery of the drug to the blood, nasal administration of Tramadol could be considered for the treatment of breakthrough pain. Ó 2011 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.
1. Introduction One important challenge in pain treatment is the achievement of a short onset of an effective analgesic action (Pinardi et al., 1998; Dursteler et al., 2006). Various strategies have been investigated to improve analgesic drug efficiency. One successful recent approach is the use of the nasal route as a portal for drug delivery. Nasal administration of Fentanyl and Ketorolac tromethamine has been recently approved by the FDA for the treatment of pain. The nasal delivery could enable non-invasive drug self-administration, overcoming the first pass-effect in the liver and increasing drug bioavailability compared to the oral route. Moreover, nasal drug administration provides an attractive needle-free alternative for the currently injectable drugs (Hinchcliffe and Illum, 1999). However, a main limitation of this route of delivery is related to the low doses that could be administered, meaning that in order to achieve efficient treatments, a high absorption of the drug from the nasal cavity is crucial. While some drugs, like Fentanyl, possess
⇑ Corresponding author. Address: Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 91120, Israel. Tel.: +972 2 6758660; fax: +972 2 6757611. E-mail address: [email protected] (E. Touitou).
excellent absorption properties through the nasal mucosa, many other molecules may require the use of appropriate delivery carriers for efficient nasal administration. For such drugs, improving nasal absorption could be a critical request. Tramadol HCl is a cationic hydrophilic molecule, with central analgesic activity. It is a synthetic analogue of codeine that binds to mu-opioid receptor and inhibits norepinephrine and serotonin reuptake (Lewis and Han, 1997). Tramadol is available as drops, capsules and sustained-release formulations for oral use, suppositories for rectal use and solution for intramuscular, intravenous and subcutaneous injection (Grond and Sablotzki, 2004). After oral administration, the drug is rapidly and extensively absorbed and metabolized in the liver. Analgesia begins within 1 h and usually reaches peak blood concentration within 2 h. In patients with moderate postoperative pain, the efficacy of IV or IM administered Tramadol is equal to that of morphine; but by the conventional oral mode of administration it is less effective for severe acute pain (Lewis and Han, 1997). Here, we present results of our investigation on the pharmacokinetic and pharmacodynamic behavior of Tramadol following administration from nasal delivery system as compared to oral aqueous solution. The delivery system was designed to be able to incorporate high concentrations of the drug and is composed of
1754-3207/$36.00 Ó 2011 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.eujps.2011.08.009
450
S. Duchi et al. / European Journal of Pain Supplements 5 (2011) 449–452
FDA approved ingredients for nasal use. The local safety of Tramadol nasal system was also tested.
Table 1 Pharmacokinetic parameters of Tramadol HCl in mice plasma (Mean ± SEM). Tramadol HCl (10 mg/kg) was administered from nasal delivery system or as oral aqueous solution.
2. Results and discussion 2.1. Tramadol levels in plasma following nasal administration in mice
Nasal delivery system
Oral aqueous solution
Cmax tmax AUC0–3h FREL%
2421 ± 651 ng/ml* 10 min 93 ± 4 lg min/ml* 198
644 ± 349 ng/ml 10 min 47 ± 2 lg min/ml
n, 16; for each experimental group. P < 0.05 nasal delivery system vs. oral aqueous solution.
*
F REL % ¼ ½ðAUCIN DOSEPO Þ=½ðAUCPO DOSEIN Þ 100
ð1Þ
These values of AUC and relative bioavailability suggest a highly improved absorption of Tramadol following the nasal delivery. 2.2. Analgesic effect of Tramadol following nasal administration in Writhing mice model The analgesic effect of Tramadol on acute nociception was investigated by using the Writhing test in mice. Tramadol HCl at a relative low drug dose of 5 mg/kg was administered in the nasal delivery system and as oral aqueous solution. The drug administration was made under different regimens: immediately before pain induction or as preventive treatment 30 min before pain induction. Mice in the control group have not received any treatment before pain induction. Immediately and 30 min after the administration, each animal was injected IP with 0.6% v/v acetic acid solution (10 ml/kg) and individually housed in a cage with a smooth flat floor. Anti-nociception was recorded by counting the number of writhes 5 min after the injection of acetic acid, for a period of
A
Oral aqueous solution
45
Control
40 Mean Writhing Episodes
The joint ethics committee (IACUC) of the Hebrew University and Hadassah Medical Center for animal welfare approved all animal study protocols. The Hebrew University is an AAALAC international accredited institute. All animal experiments were conducted in full compliance with the approved protocols. Animals were housed under normal 12-h light/dark cycle and a temperature of 21–22 °C, with food and water freely available. Tramadol HCl at a dose of 10 mg/kg was given to female C57BL/ 6J mice from nasal delivery system and from oral aqueous solution. A total of 32 mice were used; 16 for each experimental group; four mice for each time point. Quantification of Tramadol HCl in plasma samples following liquid–liquid extraction was performed by a modified method described by Gan et al. (2002), using an HPLC apparatus (Hitachi, Japan) equipped with UV variable ultraviolet detector and HSM computerized analysis program. Briefly, Tramadol detection was carried out at 220 nm on an ApolloÒ C18 5u RPC18 (5 lm particles size, 25 cm 4 mm I.D.) column, with a mobile phase containing an Acetonitrile:Phosphate Buffer 0.01 M containing 0.1% v/v Triethylamine, 22:78 v/v, adjusted at pH 3 with Orthophosphoric acid, at a flow-rate of 1 ml/min. Plasma levels of Tramadol plotted in Fig. 1 show that following nasal administration, the blood drug concentration increased rapidly with a peak at 10 min (the first time point sampled) and was much higher for the next 30 min as compared to oral (812 ± 198 and 257 ± 27 ng/ml, respectively). The higher profile was maintained up to 1 h. The pharmacokinetic parameters given in Table 1 indicate that a four time higher Cmax value was obtained by nasal drug administration vs. oral (2421 ± 651 ng/ml vs. 644 ± 349 ng/ml, respectively). This improved Cmax was obtained shortly after the administration, at 10 min (tmax) after the administration, indicating a rapid systemic absorption of the drug. A significantly higher AUC value of 93 ± 4 lg min/ml was calculated for the nasal delivery of Tramadol vs. only 47 ± 2 lg min/ml following oral drug. The relative bioavailability (FREL%) for nasal vs. oral Tramadol administration (calculated by Eq. (1)) was 198%.
Parameters
35 30
Nasal delivery system
25 20
*
15 10 5 0
Nasal delivery system
* 3000
B
Oral aqueous solution
45
Control Oral aqueous solution
40
2500
Mean Writhing Episodes
Tramadol concentration in plasma (ng/ml)
3500
2000 * 1500 1000 500
35 30 25 20
** Nasal delivery system
*
15 10 5
0 0
30
60
90
120
150
180
0
Time (min)
Fig. 1. Mean plasma levels (ng/ml, Mean ± SEM) following Tramadol HCl (10 mg/ kg) administration from: j nasal delivery system or N oral aqueous solution. n, 4; for each time point in each treatment group. ⁄P < 0.05 nasal delivery system vs. oral aqueous solution.
Fig. 2. Tramadol HCl (5 mg/kg) analgesic activity (Mean ± SD, Writhing episodes during 10 min observation) following administration from nasal delivery system or oral aqueous solution, (A) immediately or (B) 30 min before pain induction. n, 7; for each experimental group. ⁄P < 0.05 nasal delivery system vs. all groups, ⁄⁄P < 0.05 oral aqueous solution vs. untreated control group.
S. Duchi et al. / European Journal of Pain Supplements 5 (2011) 449–452
451
Fig. 3. Photomicrographs of nasal cavities excised from mice treated two times a day for 10 days with empty or Tramadol containing nasal delivery system or saline (H&E, 4000).
10 min. A writhe was indicated by abdominal constriction and stretching of at least one hind limb (Pinardi et al., 1998; Dursteler et al., 2006; Collier et al., 1968). The maximum possible effect (MPE%) of the treatments on the Writhing test was expressed as the inhibition percent of the number of writhes in a drug-treated animal, when compared to the mean number of writhes measured in a group of untreated mice (control) according to Eq. (2):
MPE% ¼ ½Mean of writhes in control group —Mean of writhes in treated group =½Mean of writhes in control group 100
ð2Þ
Results given in Fig. 2A show that oral administration of Tramadol at 5 mg/kg immediately before pain induction had no analgesic effect (no reduction in the number of writhes was observed as compared to untreated animals). On the other hand, under the same treatment regimen, Tramadol administration from nasal delivery system resulted in a significant anti-nociceptive activity and a high efficiency in suppressing the pain episodes. The maximum possible effect (MPE) value for this treatment was 67.7%. The analgesic activity of the same drug dose administered 30 min before pain induction from the nasal delivery system and after oral administration were both statistically significant as compared to the control untreated animals. However the nasal drug administration had a statistically significantly higher effect (P < 0.05), as compared to both oral and control animal groups (Fig. 2B). The nasal MPE value was more than twice higher, the values being 67.2% and 32.3% for nasal delivery and oral administration, respectively. From the above results, it can be clearly seen, that even at a low drug dose of 5 mg/kg, the effect measured following drug administration immediately before pain induction was significantly higher for the nasal delivery system as compared to oral administration. Furthermore, the nasal results indicate not only a rapid onset of the effect, but also a higher anti-nociceptive activity over time in comparison to the oral solution. It is noteworthy, that in experiments comparing the analgesic effect of Tramadol nasal delivery system to a nasal aqueous solution at the same dose, the aqueous solution had a much inferior effect at all administration regimens tested (immediately, 30 and 60 min before pain induction). Results of further experiments carried out by us (results not presented here) in larger animals, rat and sheep, sustain the efficient delivery behavior observed in this work. 2.3. Safety of Tramadol nasal delivery system administration In order to evaluate whether the Tramadol delivery system has any damaging effect on the nasal cavity and mucosa, an experiment was carried out in which three systems were nasally administrated to six mice twice a day for 10 days: saline, empty delivery
system carrier and Tramadol delivery system. At the end of the administration period, the animals were sacrificed, decapitated and the nasal cavity was removed. Samples embedded in paraffin, sectioned and stained with Hematoxylin & Eosin (H&E) were observed with a light microscope (Zeiss™, Axioskop 2 plus) for changes in appearance and structure of the nasal cavity and mucosa. Local toxicity was assessed by evaluating the histopathological alterations in the different regions of the nasal cavity (cartilage and turbinate bone, lamina propria and submucosa, mucosal epithelium and lumen). Examination of the nasal cavities excised from treated mice at the end of the experimental period showed mucosa with normal histology (intact and normal epithelium) and no inflammatory cells infiltration. Only limited and minimal non-cellular homogeneous material was observed in the lumen for all treatments (Fig. 3). 3. Conclusions Nasal administration of Tramadol in animals demonstrates that when given in a delivery system by this pathway, the drug systemic absorption could be significantly improved. Results of experiments in animal Writhing model, evaluating the drug antinociceptive effect, indicate that Tramadol nasal delivery system treatment significantly increased the analgesic effect, as compared to oral administration, both 30 min before and immediately with pain induction. The significance of these results is that nasal administration of the drug was able to increase the analgesic effect and provide a rapid onset of action, improving the pain therapy. The local safety of Tramadol nasal system was good with no histological or nasal cavity changes. The findings of this work suggest that treatment with Tramadol nasal delivery system could enhance the efficiency of the drug and shorten its onset of action relative to oral treatment, without damaging the nasal mucosal membrane. Relative to parenteral treatment, the nasal pathway administration could prevent side effects and decrease the need of patient hospitalization. Moreover, due to the rapid and efficient delivery of the drug to the blood, nasal administration of Tramadol could be considered for the treatment of breakthrough pain. 4. Conflict of interest None. References Collier HO, Dinneen LC, Johnson CA, Schneider C. The abdominal constriction response and its suppression by analgesic drugs in the mouse. Br J Pharmacol Chemother 1968;32:295–310. Dursteler C, Mases A, Fernandez V, Pol O, Puig MM. Interaction between tramadol and two anti-emetics on nociception and gastrointestinal transit in mice. Eur J Pain 2006;10:629–38.
452
S. Duchi et al. / European Journal of Pain Supplements 5 (2011) 449–452
Gan SH, Ismail R, Wan Adnan WA, Wan Z. Method development and validation of a high-performance liquid chromatographic method for tramadol in human plasma using liquid–liquid extraction. J Chromatogr B Anal Technol Biomed Life Sci 2002;772:123–9. Grond S, Sablotzki A. Clinical pharmacology of tramadol. Clin Pharmacokinet 2004;43:879–923.
Hinchcliffe M, Illum L. Intranasal insulin delivery and therapy. Adv Drug Deliv Rev 1999;35:199–234. Lewis KS, Han NH. Tramadol: a new centrally acting analgesic. Am J Health Syst Pharm 1997;54:643–52. Pinardi G, Pelissier T, Miranda HF. Interactions in the antinociceptive effect of tramadol in mice: an isobolographic analysis. Eur J Pain 1998;2:343–50.