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Comparative study of in-vitro release and bioavailability of sustained release diclofenac sodium from certain hydrophilic polymers and commercial tablets in beagle dogs
PHAMACEUTICA ACTA HELVETIAE ELSEVIER
Pharmaceutics
Acta Helvetiae 72 (1997) 159-164
Comparative study of in-vitro release and bioavailability of sustained release diclofenac sodium from certain hydrophilic polymers and commercial tablets in beagle dogs Ehab A. Hosny Department
*, Abdel Raheem M. Al-Helw, Mohammad
ofPharmaceutics,
College
A. Al-Dardiri
of Pharmacy, King Saud Unimrsity, P.O. Box 2457, Riyadh 11451, Saudi Arabia Accepted 26 February
1997
Abstract Hydrophilic colloids interact with metallic ions to yield crosslinked insoluble salts. Such principle was utilized in the preparation of diclofenac sodium beads from sodium alginate and sodium carboxymethylcellulose. Hard spherical beads of aluminum alginate and aluminum carboxymethylcellulose with a narrow particle size distribution (1.60 + 0.12 and 3.10 + 0.20 mm) and low friability (0.5 and 1.4%) respectively were obtained with high yield (80-90%) and a drug content approaching 70-80%. The type and concentration of the polymers as well as the pH of the dissolution medium were found to affect the rate of drug release. Beads prepared from Na-alginate showed a non-significantly ( p > 0.05) faster rate of drug release than that prepared from NaCMC. The higher the polymer concentration, the slower was the rate of drug release. Diclofenac sodium did not release in 0.1 N HCl (pH 1.2) for 2 h and released in phosphate buffer solution (pH 6.8) from the two formulations studied and from the commercial Voltaren Retard tablet. The two formulations of the beads resulted in a sustained release action of diclofenac sodium for 24 h. They showed K,, values of 0.02 + 0.0 1 and 0.3 * 0.0 1 h- ’ and these correspond to z,,, of 34.65 and 27.70 for the Na-alginate and NaCMC beads, respectively. They also showed mean residence time (MRT) values of 9.56 + 2.5 and 7.86 * 0.54 h, respectively. They also showed non-significant (p > 0.05) differences with respect to their plasma levels, C,,, T,, and AUC, _ 24h. The relative bioavailability of the two formulations were 59.01 and 47.96%, respectively, relative to that of the commercial Voltaren Retard tablets of Ciba-Geigy which showed a K,, of 0.044 h-’ corresponding to a i,,, of 15.75 h and MRT of 7.45 + 1.10 h. Keywords:
In-vitro release; Bioavailability;
Diclofenac
sodium; Sustained
1. Introduction Sustained are effective
release (SR) delivery systems for oral dosing in achieving ideal therapy with drugs that
have a narrow therapeutic range of blood concentration or eliminate rapidly (Nishihata et al., 1985, 1988; Nishihata, 1987). Reviews of the use of cellulose ethers in SR dosage forms have been published (Alderman, 1984; Langer and Peppas, 1987; Ranga Rao and Padmalatha Devi, 1988; Hogan, 1989). Hydrophilic matrices are becoming popular
* Corresponding
author. Fax: +966-l-4676383.
0031-6865/97/$17.00 Copyright PI! SOO3L6865(97)OOOlO-I
release; Hydrophilic
polymers;
Commercial
tablets; Beagle dogs
in the formulation of controlled-release solid dosage forms. Various types of polymers are used as the gel forming agent in matrices, such as sodium carboxymethylcellulose, hydroxypropyl-methylcellulose, hydroxypropylcellulose and methylcellulose. Sodium carboxymethylcellulose and other aqueous soluble polymers such as sodium alginate (Bodmeier and Paeratakul, 1989; Rubio and Ghaly, 19941, gelatin (Takenaka et al., 1980) and chitosan (Thanoo et al., 1992) have had their water resistance enhanced after interaction with crosslinking agents. Using a similar technique, spherical agglomerates of water-insoluble drugs were prepared by dropping drug dispersions in either chitosan or sodium
0 1997 Elsevier Science B.V. All rights reserved.
E.A. Hosny et al./Phannaceutica
160
Acta Helcetiae 72 (1997) 159-164
alginate solutions into an aqueous solution of the respective counter ions tripolyphosphate or calcium chloride (Bodmeier and Paeratakul, 1989). In pharmaceutical formulation technology, alginates have been used as tablet binders, disintegrants, viscosity-enhancing agents (McGinity et al., 19861, and as sustained-release matrices (Bodmeier and Paeratakul, 1989; Rubio and Ghaly, 1994; Valentina and Gilberto, 199.5). Diclofenac sodium, a non-steroidal anti-inflammatory drug, has an unpleasant taste and causes gastric irritation. As this drug is mainly absorbed from the gastrointestinal tract (Reynolds, 1989), an enteric coating provides sufficient taste masking without negatively affecting the availability of the drug. Furthermore, the formulation of a multiparticulate system is thought to be preferable to a single-unit dosage form because the small particles spread out more uniformly in the gastrointestinal tract. This results in a more reproducible drug absorption and reduces the risk of local irritations. A process had hence to be selected which is applicable to the coating of these small particles. In the present study, a technique was used to prepare sustained-release beads containing diclofenac sodium in an aqueous environment. Sodium alginate and sodium carboxymethyl-cellulose were used in the preparation of the beads. The physical properties of the beads as well as the in-vitro release of the drug from the two matrices were evaluated. The bioavailability of the two experimental formulations in addition to that of the commercial Voltaren Retard tablets of Ciba-Geigy was also studied in beagle dogs.
ous solution (l-3% w/v) through a disposable syringe into a beaker placed on a magnetic stirrer and containing 10 ml of the curing solution (AlC1,6H,O, 5% w/v> dispersed in 20 ml of n-heptan using 0.1 g of Tween 20. Both the stirring rate (500 rpm) and temperature (25°C) were maintained constant throughout the curing time (5 min). The liquid phase was decanted and the formed beads were filtered, washed quickly with acetone and air dried for 24 h.
2. Experimental
2.2.5. Particle size analysis The particle size distribution was carried out by counting a sample of 100 beads per batch and measuring the projected diameter by a projected microscope (ReichertJung, No. 386522, Austria).
procedures
2. I. Chemicals Diclofenac sodium was supplied as courtesy by SPIMAC0 (Saudi Arabia). Low viscosity sodium carboxymethylcellulose (NaCMC) from BDH Chemicals (England). Sodium alginate MW about 115,000 from Fluka Chemie (Switzerland). Aluminum chloride hexahydrate (AlC1,6H,O) from Carlo Erba (Italy). Polyoxyethylene sorbitan monolaurate (Tween 20) from Atlas Europol (Italy). Votaren Retard tablets were kindly provided by Ciba-Geigy (Saudi Arabia). All the materials were used as supplied by the manufacturers. All other solvents and reagents were of analytical or HPLC grade. 2.2. Methods 2.2.1. Preparation of aluminum-CMC beads The beads were prepared by extruding dropwise a dispersion of diclofenac sodium (3% w/v> in NaCMC aque-
2.2.2. Preparation of aluminum alginate beads Diclofenac sodium (3% w/v) was dispersed into an aqueous solution of sodium alginate (l-3% w/v) in deionized distilled water. The beads were formed by dropping the dispersion through a disposable syringe onto a gently agitated (500 rpm) aqueous solution of aluminum chloride (5% w/v>. The gelled beads were separated after 5 min, rinsed with deionized distilled water and air dried for 24 h. 2.2.3. Drug content The diclofenac sodium content of either beads prepared was determined by powdering 50 mg of the obtained beads in a mortar. The drug was then extracted several times with phosphate buffer solution (pH 7.4). The filtered solutions after completion to 100 ml with phosphate buffer were assayed spectrophotometrically at 276 nm. All the data are the means of three determinations. 2.2.4. Disintegration test of SR products The disintegration time in minutes was determined at 37°C in 900 ml of phosphate buffer pH 7.4 and 0.1 N HCl using Erweka disintegration tester ZT4 (Germany).
2.2.6. Friability test The friability of the prepared beads was determined in an Erweka TA3R friabilator (Erweka Apparatebau, Germany) using 500 mg beads, 25 rpm for 4 min. 2.2.7. In-vitro dissolution studies Dissolution of aluminum alginate and aluminum-CMC beads and Voltaren Retard tablets was carried out using the equivalent of 100 mg diclofenac sodium. The dissolution studies were performed using the USP dissolution apparatus II with 100 rpm paddle rotational speed. The dissolution test was carried out at 37 + 0.5”C in 750 ml of 0.1 N HCl (pH 1.2) for 2 h and continued for another 8 h
E.A. Hosny et al./ Pharnmceutica
at pH 6.8. The change in pH was achieved by the addition of 250 ml of 0.2 M tribasic sodium phosphate. The drug concentration and the percentage released were determined every 30 mitt, at 276 nm using Philips PU 8620 spectrophotometer connected to an IBM computer Model PS 30 using TDS software from Philips (England). The in-vitro release studies were performed in triplicate for each of the prepared beads formulations and for the commercial Voltaren Retard tablets of Ciba-Geigy. 2.2.8. Animal studies Five male beagle dogs weighing 11.80 f 1.55 kg were used in this study. One hundred mg diclofenac sodium in the form of aluminum alginate, aluminum-CMC beads or Voltaren Retard tablets were administered to these dogs on three occasions. Two weeks were allowed between the successive dosings. The dogs remained in good health throughout the entire period of study. The dogs were starved for 18 h prior to the experiment but water was allowed ad libitum. During the experimental period each dog was placed in an upright position in a restrainer stand. The legs were shaven and a cephalic vein was cannulated using an 18 gauge cannula. Five ml blood samples were withdrawn into heparinized vaccutainer tubes before and at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10, 12 and 24 h after oral administration of the encapsulated beads or the commercial Voltaren Retard tablets. The tubes were centrifuged for 10 min, and plasma was aspirated and kept frozen pending analysis. 2.2.9. Assay method of diclofenac sodium The concentrations of diclofenac sodium in plasma samples were assayed using a specific and sensitive HPLC assay method (El-Sayed et al., 1988). The method involved the use of 50 ~1 aliquots of flufenamic acid as the internal standard (500 ng) to be added to plasma samples. After vortexing for 1 min, 5 ml of acetonitrile was added to precipitate the plasma protein. After centrifugation for 5 min at 5000 rev the supematant was transferred to a 10 ml centrifuge tube and evaporated to dryness. The residue was reconstituted in 300 ~1 of HPLC eluent (acetonitrile:water in 50:50 v/v adjusted to pH 3 with glacial acetic acid) and injected into the loop injector. 2.2.10. Pharmacokinetic analysis The maximum plasma concentration (C,,,) and the time to reach that maximum (T,,,) were determined as mean f standard deviation (X k SD) from the plasma concentration-time profiles of each of the five dogs. The area under the plasma concentration-time curve up to the last sampling time (AUC, ~ 24h) and the area under the first moment curve (AUMC, ~ 24h) were determined using the
Acta Helvetiae 72 (1997) 159-164
161
linear trapezoidal rule. The apparent elimination rate constant (K,,) was calculated by the technique of least-squares regression analysis. The mean residence time of diclofenac sodium in the body (MRT) after oral administration of both formulations and the commercial Voltaren Retard tablets was calculated using the following equation: MRT = AUMC/AUC
2.2.11. Statistical analysis The significance of the difference between the pharmacokinetic parameters obtained after oral administration to the five beagle dogs of the aluminum alginate, aluminumCMC beads or the commercial Voltaren Retard tablets was evaluated using the analysis of variance (ANOVA) on a microcomputer statistical package @AS, Statistical Analysis System). The differences were considered significant at p-values of 0.05. Furthermore, the data were analyzed by Fisher’s least significant difference (LSD) method to reveal any significant difference between the formulations. All the pharmacokinetic parameters were expressed as mean k SD.
3. Results and discussion In the present study beads of diclofenac sodium were successfully prepared from the two formulations by dropping the drug dispersions of sodium carboxymethylcellulose or sodium alginate onto an aqueous solutions of aluminum chloride. The formed beads were fairly rounded spheres because the droplets instantaneously formed gelled whereas by ionotropic gelation of the polysacharides with the oppositely charged ions (Valentina and Gilberto, 1995). The sodium ions of Na-alginate or NaCMC were replaced by aluminum ions. These would form insoluble polymers entrapping the drug inside the obtained structure and allowing the drug to be released at a slow rate (Bodmeier and Paeratakul, 1989). The gel formation could be visually observed as transparent spherical bodies appeared with a distinct boundary between the gel beads and the bulk phase. The obtained products were rounded in shape and the size of the beads varied. Generally, the shape and the size of the beads were affected mainly by the type and the concentration of the used polymer. It is worth mentioning that higher Na-alginate concentration (3% w/v> yielded massive irregular hard beads with a very low friability value (0.5%). While lower concentrations (1 and 2% w/v) yielded beads with different shapes and a friability of less than 1%. On the other hand, the higher concentrations of NaCMC (3% w/v) produced more uniform and rounded
E.A. Hosny et al. /Pharmaceutics
162
Acta Heluetiae 72 (1997) 159-164
beads than the lower concentrations (1 and 2% w/v>. Within the same concentrations of the used polymers, aluminum-CMC beads showed slightly higher friability values than beads prepared from Na-alginate (0.75 1.40%). This could be attributed to the difference in the binding force of the two polymers. The results obtained in Table 1 show that the particle size of aluminum alginate beads ranges between 1.60-2.40 mm and the particle size of the beads slightly increased with the increase in the polymer level from 1 to 3% w/v. Aluminum carboxymethylcellulose beads showed a larger particle diameter that ranged between 2.10 and 3.10 mm. This could be attributed to the higher viscosity of NaCMC solution (viscosity of 1% solution in water at 20°C according to the British Standard 188, 1957, is 30-70 c/s, U-tube viscometer). The drug content determinations did not show a significant difference between the different batches indicating that the variation in Na-alginate or NaCMC concentrations has no effect on the drug content. The entrapment efficiency of diclofenac sodium within the two used polymers was about 70-80%, indicating high drug loading for all the batches. However, a small amount of the drug was lost from aluminum-CMC beads during the recovery due to its solubility in the external phase. The ionic character of the polysacharides resulted in pH-dependent disintegration of the beads. Both aluminum alginate and aluminum carboxymethylcellulose stayed intact in 0.1 N HCl and did not disintegrate within 24 h, but rapidly disintegrated in phosphate buffer solution (pH 7.4) as shown in Table 1. Air dried beads disintegrated within 25-60 min according to the polymer type and concentration. Aluminum carboxymethylcellulose beads showed longer disintegration times than the corresponding beads prepared from Na-alginate. This could be due to the difference in the solubility of the two polymers in the disintegrating medium (pH 7.4). Beads containing larger amounts of polymer (3% w/v) disintegrated slower than those containing smaller amounts (1 and 2% w/v). This could
Table 1 Evaluation 4-6)
of diclofenac
80
t
60
-
40
-
20
F
0
1
2
3
5 Time
6
7
6
9
10
(h)
Fig. 1. The percent (X +SD) diclofenac sodium released from the commercial Voltaren Retard tablets and the effect of sodium alginate concentration on the release of the drug from beads in 0.1 N HCl and in phosphate buffer solution.
be attributed to the time required for eroding the beads (Simon et al., 1994). Dissolution studies were carried out to study the effect of the type and the concentration of the polymer, and the pH of the dissolution medium on the release of diclofenac sodium from the beads formulations in comparison to the release from the commercial Voltaren Retard tablets of Ciba-Geigy. The obtained results in Figs. 1 and 2 show the release of the drug from aluminum alginate and aluminum carboxymethylcellulose beads, respectively in 0.1 N HCl (pH 1.2) and in phosphate buffer solution (pH 6.8) in comparison to that from the commercial tablets. The figures show that the amount of drug released in 0.1 N HCl was negligible because diclofenac sodium has a limited solubility in the acidic medium (Reynolds, 1989). On the other hand, in alkaline phosphate buffer solution, the drug was rapidly released from the disintegrated aluminum alginate beads due to its high solubility in the alkaline medium. The results also show that the shorter disintegration time of aluminum alginate beads leads to the faster release rate of diclofenac sodium. On the other hand, the
sodium sustained release beads prepared using sodium alginate (batch Nos. l-3)
and sodium carboxymethylcellulose
Batch No.
Mean particle diameter (mm + SD)
No. of beads in 100 mg sample
Drug content in beads
Polymer level
(mg/g
(a w/v)
1 2 3 4 5 6
1.60f0.12 1.90*0.15 2.4OkO.16 2.10i0.13 2.6OkO.12 3.10+0.21
48 36 31 20 16 10
724*3.1 746 f 3.6 791 +4.2 735 + 2.9 634 i 4.2 714il.l
X &SD)
4
1 2 3
I 2 3
Disintegration time (min) 25.20 34.10 40.20 32.30 48.10 60.20
(batch Nos.
Friability (%I 0.85 0.55 0.50
1.40 1.00 0.75
E.A. nosny 100
et al. / Pharmaceutics
r
$
80
-
P!-l 1.2
e s B P
60-
x
40-
i 9 g
20
-
0
2
1
163
Table 2 Mean (X f SD> pharmacokinetic parameters of diclofenac sodium following oral administration of aluminum alginate beads, aluminum-CMC beads and commercial tablets (containing 100 mg diclofenac sodium) to five fasting beagle dogs
m $
Acta Helaetiae 72 (1997) 159-164
3
4
5 Time
0
Na
A
Na CMC
’
NeCMC3%
6
7
CMC
5
1% 2%
9
Parameter
Al-alginate
Al-CMC
Commercial tablets
AUC ( /Lg h/ml)
48.99 f 11.07 7.0 * 1.37 2.0 f 1.35 9.56 + 2.50 0.02 + 0.01 59.01
39.82* 26.61 5.43k2.91 1.70+0.!34 7.86 + 0.54 0.03 i 0.01 47.96
83.29? 18.31 15.98k4.31 3.60& 1.52 7.45 + 1.10 0.044 k 0.004
C,,,( wg/ml) T,,, (h) MRT (h) 10
(h)
K,, (h-l) Rel. bioavailability (%I
Fig. 2. Effect of sodium carboxymethylcellulose concentration on the release of diclofenac sodium (X &SD> from beads in 0.1 N HCl and in phosphate buffer solution.
drug was slowly released from aluminum carboxymethylcellulose beads due to their slow disintegration (Table 1). The release of diclofenac sodium from the commercial Voltaren Retard tablets was the slowest as it released about 72% of the drug content in 10 h of dissolution. The concentration of the polymer used in the preparation of beads was found to affect the drug release. The dissolution results in Figs. 1 and 2 show that the higher the polymer concentration, the slower was the rate of drug release. Fig. 3 shows the mean (X + SEM) plasma-concentration time profiles of diclofenac sodium that resulted after oral administration of either aluminum-CMC beads, aluminum alginate beads or the commercial Voltaren Retard tablets to each of the five beagle dogs. The results show that the absorption of diclofenac sodium was fast as it appears in plasma samples withdrawn after 0.5 h in all
0
4
8
12
16
20
24
Time fh)
Fig. 3. Plasma concentration (X &SEMI of diclofenac sodium after oral administration of aluminum-CMC and aluminum alginate beads and the commercial Voltaren Retard tablets to five beagle dogs.
dogs from both formulations and the commercial tablets. It reaches C,,, within l-4 h in case of aluminum alginate beads with a mean T,,, of 2.0 + 1.35 h and a C,,, of 7.0 If: 1.37 pug/ml. While after administration of aluminum-CMC beads the C,,, was reached within l-3 h with a mean T,,, of 1.7 + 0.84 h and a C,,, of 5.43 + 2.91 pg/ml. While the commercial Voltaren Retard tablets showed a C,,, of 15.98 f 4.31 pg/ml within 2-6 h after administration with a mean T,,, of 3.6 + 1.52 h. The two beads formulations were non-significantly different (P > 0.05) with regards to C,,, , T,,, , AUC and plasma concentrations. Table 2 shows that the two formulations were also bioequivalent to each other where the aluminum alginate beads gave an area under the plasma concentration-time curve up to the last measurable concentration (AUC, _ 24h) of 48.99 + 11.07 pg h/ml compared to aluminum-CMC beads that gave an AUC0_24b of 39.82 + 26.61 pg h/ml. The two formulations showed a sustained plasma levels for the time of study i.e. for 24 h. The variations in AUCs were greater between dogs on administration of the aluminum-CMC beads than after administration of the alginate ones, showing coefficient of variations of 65.14 and 19.57%, respectively. While the coefficient of variations after administration of Voltaren tablets was 22.06%. The apparent elimination rate constants calculated by the least-squares regression analysis were 0.02 + 0.01, 0.03 + 0.01 and 0.04 + 0.00 h-’ for the aluminum alginate beads, aluminum-CMC-beads and commercial Voltaren Retard tablets, respectively. These formulations resulted in an MRT of 9.56 + 2.50, 7.86 & 0.54 and 7.45 f 1.10 h, respectively. These values show that the prepared beads are non-significantly different ( p > 0.05) from the commercial tablets with respect to their residence time of the drug in the body and even producing a non-significantly prolonged effect more than that of the commercial tablets.
164
E.A. Hosny et al./Pharmaceutica
In conclusion, based on both the in-vitro and in-vivo data the two polymers (NaCMC and Na-alginate) were able to form S.R. beads, and the resulting S.R. formulations of diclofenac sodium in the form of aluminum alginate or aluminum-CMC beads showed a relative bioavailability of 59.01 and 47.96%, respectively, compared to that of the commercial Voltaren Retard tablets of Ciba-Geigy which showed an AUC of 83.02 k 18.31 Fg h/ml.
References Alderman, D.A., 1984. A Review of cellulose ethers in hydrophilic matrices for oral controlled-release dosage forms. Int. J. Pharm. Tech. Prod. Manufact. 5, l-9. Bodmeier, R., Paeratakul, O., 1989. Spherical agglomerates of water-insoluble drugs. J. Pharm. Sci. 78, 964-967. El-Sayed, Y.M., Abdel-Hamid, M.E., Suleiman, M.S., Najib, N.M., 1988. A rapid and sensitive high-performance liquid chromatographic method for the determination of diclofenac sodium in serum and its use in pharmacokinetic studies. J. Pharm. Pharmacol. 40, 727-729. Hogan, J.E., 1989. Hydroxypropylmethylcellulose sustained-release technology Drug Dev. Ind. Pharm. 15, 975-1000. Langer, R.S., Peppas, N.A., 1987. Present and future applications of biomaterials in controlled drug delivery. Biomaterials 2, 201-214. McGinity, J.W., Harris, M.R., Dusch, R., 1986. In: Handbook of Pharmaceutical Excipients. American Pharmaceutical Association, Washington, DC, p. 5.
Acta Helvetiae 72 (1997) 159-164 Nishihata, T., 1987. Simple formulation of sustained-release tablets of sodium diclofenac and examination in humans. Int. J. Pharm. 40, 1255128. Nishihata, T., Wada, H., Kamada, A., 1985. Sustained-release of sodium diclofenac from suppository. Int. Pharm. 27, 245-253. Nishihata, T., Hirotani, Y., Yamazi, A., Takahashi, K., Yoshitomo, H., 1988. Preliminary study on sustained-release particles prepared with hydrogenated soya phospholipid and cholesterol. Int. J. Pharm. 42, 257-260. Ranga Rao, K.V., Padmalatha Devi, K., 1988. Swelling controlled-release systems: Recent development and applicants. Int. J. Pharm. 48, 1- 13. Reynolds, R.H.F., ‘Martindale’ The Extra Pharmacopoeia, 29th ed. The Pharmaceutical Press, London, 1989, p. 250. Rubio, M.R., Ghaly, ES., 1994. In-vitro release of acetaminophen from sodium alginate controlled release pellets. Drug Dev. Ind. Pharm. 20, 1239-1251. Simon, L.D., Ruiz-Cardona, L., Topp, E.M., Stella, V.J., 1994. Effect of pH on theophylline release from partially esterified alginic acid matrices. Drug Dev. Ind. Pharm. 20, 2341-2351. Takenaka, H., Kamashima, Y., Lin, S.Y., 1980. Micromeritic properties of sulfamethoxazole microcapsules prepared by gelatin acacia coacervation. J. Pharm. Sci. 69, 513-516. Thanoo, C.B., Sunny, C.M., Jayakrishnan, A., 1992. Cross-linked chitosan microspheres: Preparation and evaluation as a matrix for the controlled release of pharmaceuticals. J. Pharm. Pharmacol. 44, 283286. Valentina, I., Gilberto, G., 1995. Bead coating process via an excess of crosslinking agent. Drug Dev. Ind. Pharm. 21, 2307-2322.
Pharmaceutics
Acta Helvetiae 72 (1997) 159-164
Comparative study of in-vitro release and bioavailability of sustained release diclofenac sodium from certain hydrophilic polymers and commercial tablets in beagle dogs Ehab A. Hosny Department
*, Abdel Raheem M. Al-Helw, Mohammad
ofPharmaceutics,
College
A. Al-Dardiri
of Pharmacy, King Saud Unimrsity, P.O. Box 2457, Riyadh 11451, Saudi Arabia Accepted 26 February
1997
Abstract Hydrophilic colloids interact with metallic ions to yield crosslinked insoluble salts. Such principle was utilized in the preparation of diclofenac sodium beads from sodium alginate and sodium carboxymethylcellulose. Hard spherical beads of aluminum alginate and aluminum carboxymethylcellulose with a narrow particle size distribution (1.60 + 0.12 and 3.10 + 0.20 mm) and low friability (0.5 and 1.4%) respectively were obtained with high yield (80-90%) and a drug content approaching 70-80%. The type and concentration of the polymers as well as the pH of the dissolution medium were found to affect the rate of drug release. Beads prepared from Na-alginate showed a non-significantly ( p > 0.05) faster rate of drug release than that prepared from NaCMC. The higher the polymer concentration, the slower was the rate of drug release. Diclofenac sodium did not release in 0.1 N HCl (pH 1.2) for 2 h and released in phosphate buffer solution (pH 6.8) from the two formulations studied and from the commercial Voltaren Retard tablet. The two formulations of the beads resulted in a sustained release action of diclofenac sodium for 24 h. They showed K,, values of 0.02 + 0.0 1 and 0.3 * 0.0 1 h- ’ and these correspond to z,,, of 34.65 and 27.70 for the Na-alginate and NaCMC beads, respectively. They also showed mean residence time (MRT) values of 9.56 + 2.5 and 7.86 * 0.54 h, respectively. They also showed non-significant (p > 0.05) differences with respect to their plasma levels, C,,, T,, and AUC, _ 24h. The relative bioavailability of the two formulations were 59.01 and 47.96%, respectively, relative to that of the commercial Voltaren Retard tablets of Ciba-Geigy which showed a K,, of 0.044 h-’ corresponding to a i,,, of 15.75 h and MRT of 7.45 + 1.10 h. Keywords:
In-vitro release; Bioavailability;
Diclofenac
sodium; Sustained
1. Introduction Sustained are effective
release (SR) delivery systems for oral dosing in achieving ideal therapy with drugs that
have a narrow therapeutic range of blood concentration or eliminate rapidly (Nishihata et al., 1985, 1988; Nishihata, 1987). Reviews of the use of cellulose ethers in SR dosage forms have been published (Alderman, 1984; Langer and Peppas, 1987; Ranga Rao and Padmalatha Devi, 1988; Hogan, 1989). Hydrophilic matrices are becoming popular
* Corresponding
author. Fax: +966-l-4676383.
0031-6865/97/$17.00 Copyright PI! SOO3L6865(97)OOOlO-I
release; Hydrophilic
polymers;
Commercial
tablets; Beagle dogs
in the formulation of controlled-release solid dosage forms. Various types of polymers are used as the gel forming agent in matrices, such as sodium carboxymethylcellulose, hydroxypropyl-methylcellulose, hydroxypropylcellulose and methylcellulose. Sodium carboxymethylcellulose and other aqueous soluble polymers such as sodium alginate (Bodmeier and Paeratakul, 1989; Rubio and Ghaly, 19941, gelatin (Takenaka et al., 1980) and chitosan (Thanoo et al., 1992) have had their water resistance enhanced after interaction with crosslinking agents. Using a similar technique, spherical agglomerates of water-insoluble drugs were prepared by dropping drug dispersions in either chitosan or sodium
0 1997 Elsevier Science B.V. All rights reserved.
E.A. Hosny et al./Phannaceutica
160
Acta Helcetiae 72 (1997) 159-164
alginate solutions into an aqueous solution of the respective counter ions tripolyphosphate or calcium chloride (Bodmeier and Paeratakul, 1989). In pharmaceutical formulation technology, alginates have been used as tablet binders, disintegrants, viscosity-enhancing agents (McGinity et al., 19861, and as sustained-release matrices (Bodmeier and Paeratakul, 1989; Rubio and Ghaly, 1994; Valentina and Gilberto, 199.5). Diclofenac sodium, a non-steroidal anti-inflammatory drug, has an unpleasant taste and causes gastric irritation. As this drug is mainly absorbed from the gastrointestinal tract (Reynolds, 1989), an enteric coating provides sufficient taste masking without negatively affecting the availability of the drug. Furthermore, the formulation of a multiparticulate system is thought to be preferable to a single-unit dosage form because the small particles spread out more uniformly in the gastrointestinal tract. This results in a more reproducible drug absorption and reduces the risk of local irritations. A process had hence to be selected which is applicable to the coating of these small particles. In the present study, a technique was used to prepare sustained-release beads containing diclofenac sodium in an aqueous environment. Sodium alginate and sodium carboxymethyl-cellulose were used in the preparation of the beads. The physical properties of the beads as well as the in-vitro release of the drug from the two matrices were evaluated. The bioavailability of the two experimental formulations in addition to that of the commercial Voltaren Retard tablets of Ciba-Geigy was also studied in beagle dogs.
ous solution (l-3% w/v) through a disposable syringe into a beaker placed on a magnetic stirrer and containing 10 ml of the curing solution (AlC1,6H,O, 5% w/v> dispersed in 20 ml of n-heptan using 0.1 g of Tween 20. Both the stirring rate (500 rpm) and temperature (25°C) were maintained constant throughout the curing time (5 min). The liquid phase was decanted and the formed beads were filtered, washed quickly with acetone and air dried for 24 h.
2. Experimental
2.2.5. Particle size analysis The particle size distribution was carried out by counting a sample of 100 beads per batch and measuring the projected diameter by a projected microscope (ReichertJung, No. 386522, Austria).
procedures
2. I. Chemicals Diclofenac sodium was supplied as courtesy by SPIMAC0 (Saudi Arabia). Low viscosity sodium carboxymethylcellulose (NaCMC) from BDH Chemicals (England). Sodium alginate MW about 115,000 from Fluka Chemie (Switzerland). Aluminum chloride hexahydrate (AlC1,6H,O) from Carlo Erba (Italy). Polyoxyethylene sorbitan monolaurate (Tween 20) from Atlas Europol (Italy). Votaren Retard tablets were kindly provided by Ciba-Geigy (Saudi Arabia). All the materials were used as supplied by the manufacturers. All other solvents and reagents were of analytical or HPLC grade. 2.2. Methods 2.2.1. Preparation of aluminum-CMC beads The beads were prepared by extruding dropwise a dispersion of diclofenac sodium (3% w/v> in NaCMC aque-
2.2.2. Preparation of aluminum alginate beads Diclofenac sodium (3% w/v) was dispersed into an aqueous solution of sodium alginate (l-3% w/v) in deionized distilled water. The beads were formed by dropping the dispersion through a disposable syringe onto a gently agitated (500 rpm) aqueous solution of aluminum chloride (5% w/v>. The gelled beads were separated after 5 min, rinsed with deionized distilled water and air dried for 24 h. 2.2.3. Drug content The diclofenac sodium content of either beads prepared was determined by powdering 50 mg of the obtained beads in a mortar. The drug was then extracted several times with phosphate buffer solution (pH 7.4). The filtered solutions after completion to 100 ml with phosphate buffer were assayed spectrophotometrically at 276 nm. All the data are the means of three determinations. 2.2.4. Disintegration test of SR products The disintegration time in minutes was determined at 37°C in 900 ml of phosphate buffer pH 7.4 and 0.1 N HCl using Erweka disintegration tester ZT4 (Germany).
2.2.6. Friability test The friability of the prepared beads was determined in an Erweka TA3R friabilator (Erweka Apparatebau, Germany) using 500 mg beads, 25 rpm for 4 min. 2.2.7. In-vitro dissolution studies Dissolution of aluminum alginate and aluminum-CMC beads and Voltaren Retard tablets was carried out using the equivalent of 100 mg diclofenac sodium. The dissolution studies were performed using the USP dissolution apparatus II with 100 rpm paddle rotational speed. The dissolution test was carried out at 37 + 0.5”C in 750 ml of 0.1 N HCl (pH 1.2) for 2 h and continued for another 8 h
E.A. Hosny et al./ Pharnmceutica
at pH 6.8. The change in pH was achieved by the addition of 250 ml of 0.2 M tribasic sodium phosphate. The drug concentration and the percentage released were determined every 30 mitt, at 276 nm using Philips PU 8620 spectrophotometer connected to an IBM computer Model PS 30 using TDS software from Philips (England). The in-vitro release studies were performed in triplicate for each of the prepared beads formulations and for the commercial Voltaren Retard tablets of Ciba-Geigy. 2.2.8. Animal studies Five male beagle dogs weighing 11.80 f 1.55 kg were used in this study. One hundred mg diclofenac sodium in the form of aluminum alginate, aluminum-CMC beads or Voltaren Retard tablets were administered to these dogs on three occasions. Two weeks were allowed between the successive dosings. The dogs remained in good health throughout the entire period of study. The dogs were starved for 18 h prior to the experiment but water was allowed ad libitum. During the experimental period each dog was placed in an upright position in a restrainer stand. The legs were shaven and a cephalic vein was cannulated using an 18 gauge cannula. Five ml blood samples were withdrawn into heparinized vaccutainer tubes before and at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10, 12 and 24 h after oral administration of the encapsulated beads or the commercial Voltaren Retard tablets. The tubes were centrifuged for 10 min, and plasma was aspirated and kept frozen pending analysis. 2.2.9. Assay method of diclofenac sodium The concentrations of diclofenac sodium in plasma samples were assayed using a specific and sensitive HPLC assay method (El-Sayed et al., 1988). The method involved the use of 50 ~1 aliquots of flufenamic acid as the internal standard (500 ng) to be added to plasma samples. After vortexing for 1 min, 5 ml of acetonitrile was added to precipitate the plasma protein. After centrifugation for 5 min at 5000 rev the supematant was transferred to a 10 ml centrifuge tube and evaporated to dryness. The residue was reconstituted in 300 ~1 of HPLC eluent (acetonitrile:water in 50:50 v/v adjusted to pH 3 with glacial acetic acid) and injected into the loop injector. 2.2.10. Pharmacokinetic analysis The maximum plasma concentration (C,,,) and the time to reach that maximum (T,,,) were determined as mean f standard deviation (X k SD) from the plasma concentration-time profiles of each of the five dogs. The area under the plasma concentration-time curve up to the last sampling time (AUC, ~ 24h) and the area under the first moment curve (AUMC, ~ 24h) were determined using the
Acta Helvetiae 72 (1997) 159-164
161
linear trapezoidal rule. The apparent elimination rate constant (K,,) was calculated by the technique of least-squares regression analysis. The mean residence time of diclofenac sodium in the body (MRT) after oral administration of both formulations and the commercial Voltaren Retard tablets was calculated using the following equation: MRT = AUMC/AUC
2.2.11. Statistical analysis The significance of the difference between the pharmacokinetic parameters obtained after oral administration to the five beagle dogs of the aluminum alginate, aluminumCMC beads or the commercial Voltaren Retard tablets was evaluated using the analysis of variance (ANOVA) on a microcomputer statistical package @AS, Statistical Analysis System). The differences were considered significant at p-values of 0.05. Furthermore, the data were analyzed by Fisher’s least significant difference (LSD) method to reveal any significant difference between the formulations. All the pharmacokinetic parameters were expressed as mean k SD.
3. Results and discussion In the present study beads of diclofenac sodium were successfully prepared from the two formulations by dropping the drug dispersions of sodium carboxymethylcellulose or sodium alginate onto an aqueous solutions of aluminum chloride. The formed beads were fairly rounded spheres because the droplets instantaneously formed gelled whereas by ionotropic gelation of the polysacharides with the oppositely charged ions (Valentina and Gilberto, 1995). The sodium ions of Na-alginate or NaCMC were replaced by aluminum ions. These would form insoluble polymers entrapping the drug inside the obtained structure and allowing the drug to be released at a slow rate (Bodmeier and Paeratakul, 1989). The gel formation could be visually observed as transparent spherical bodies appeared with a distinct boundary between the gel beads and the bulk phase. The obtained products were rounded in shape and the size of the beads varied. Generally, the shape and the size of the beads were affected mainly by the type and the concentration of the used polymer. It is worth mentioning that higher Na-alginate concentration (3% w/v> yielded massive irregular hard beads with a very low friability value (0.5%). While lower concentrations (1 and 2% w/v) yielded beads with different shapes and a friability of less than 1%. On the other hand, the higher concentrations of NaCMC (3% w/v) produced more uniform and rounded
E.A. Hosny et al. /Pharmaceutics
162
Acta Heluetiae 72 (1997) 159-164
beads than the lower concentrations (1 and 2% w/v>. Within the same concentrations of the used polymers, aluminum-CMC beads showed slightly higher friability values than beads prepared from Na-alginate (0.75 1.40%). This could be attributed to the difference in the binding force of the two polymers. The results obtained in Table 1 show that the particle size of aluminum alginate beads ranges between 1.60-2.40 mm and the particle size of the beads slightly increased with the increase in the polymer level from 1 to 3% w/v. Aluminum carboxymethylcellulose beads showed a larger particle diameter that ranged between 2.10 and 3.10 mm. This could be attributed to the higher viscosity of NaCMC solution (viscosity of 1% solution in water at 20°C according to the British Standard 188, 1957, is 30-70 c/s, U-tube viscometer). The drug content determinations did not show a significant difference between the different batches indicating that the variation in Na-alginate or NaCMC concentrations has no effect on the drug content. The entrapment efficiency of diclofenac sodium within the two used polymers was about 70-80%, indicating high drug loading for all the batches. However, a small amount of the drug was lost from aluminum-CMC beads during the recovery due to its solubility in the external phase. The ionic character of the polysacharides resulted in pH-dependent disintegration of the beads. Both aluminum alginate and aluminum carboxymethylcellulose stayed intact in 0.1 N HCl and did not disintegrate within 24 h, but rapidly disintegrated in phosphate buffer solution (pH 7.4) as shown in Table 1. Air dried beads disintegrated within 25-60 min according to the polymer type and concentration. Aluminum carboxymethylcellulose beads showed longer disintegration times than the corresponding beads prepared from Na-alginate. This could be due to the difference in the solubility of the two polymers in the disintegrating medium (pH 7.4). Beads containing larger amounts of polymer (3% w/v) disintegrated slower than those containing smaller amounts (1 and 2% w/v). This could
Table 1 Evaluation 4-6)
of diclofenac
80
t
60
-
40
-
20
F
0
1
2
3
5 Time
6
7
6
9
10
(h)
Fig. 1. The percent (X +SD) diclofenac sodium released from the commercial Voltaren Retard tablets and the effect of sodium alginate concentration on the release of the drug from beads in 0.1 N HCl and in phosphate buffer solution.
be attributed to the time required for eroding the beads (Simon et al., 1994). Dissolution studies were carried out to study the effect of the type and the concentration of the polymer, and the pH of the dissolution medium on the release of diclofenac sodium from the beads formulations in comparison to the release from the commercial Voltaren Retard tablets of Ciba-Geigy. The obtained results in Figs. 1 and 2 show the release of the drug from aluminum alginate and aluminum carboxymethylcellulose beads, respectively in 0.1 N HCl (pH 1.2) and in phosphate buffer solution (pH 6.8) in comparison to that from the commercial tablets. The figures show that the amount of drug released in 0.1 N HCl was negligible because diclofenac sodium has a limited solubility in the acidic medium (Reynolds, 1989). On the other hand, in alkaline phosphate buffer solution, the drug was rapidly released from the disintegrated aluminum alginate beads due to its high solubility in the alkaline medium. The results also show that the shorter disintegration time of aluminum alginate beads leads to the faster release rate of diclofenac sodium. On the other hand, the
sodium sustained release beads prepared using sodium alginate (batch Nos. l-3)
and sodium carboxymethylcellulose
Batch No.
Mean particle diameter (mm + SD)
No. of beads in 100 mg sample
Drug content in beads
Polymer level
(mg/g
(a w/v)
1 2 3 4 5 6
1.60f0.12 1.90*0.15 2.4OkO.16 2.10i0.13 2.6OkO.12 3.10+0.21
48 36 31 20 16 10
724*3.1 746 f 3.6 791 +4.2 735 + 2.9 634 i 4.2 714il.l
X &SD)
4
1 2 3
I 2 3
Disintegration time (min) 25.20 34.10 40.20 32.30 48.10 60.20
(batch Nos.
Friability (%I 0.85 0.55 0.50
1.40 1.00 0.75
E.A. nosny 100
et al. / Pharmaceutics
r
$
80
-
P!-l 1.2
e s B P
60-
x
40-
i 9 g
20
-
0
2
1
163
Table 2 Mean (X f SD> pharmacokinetic parameters of diclofenac sodium following oral administration of aluminum alginate beads, aluminum-CMC beads and commercial tablets (containing 100 mg diclofenac sodium) to five fasting beagle dogs
m $
Acta Helaetiae 72 (1997) 159-164
3
4
5 Time
0
Na
A
Na CMC
’
NeCMC3%
6
7
CMC
5
1% 2%
9
Parameter
Al-alginate
Al-CMC
Commercial tablets
AUC ( /Lg h/ml)
48.99 f 11.07 7.0 * 1.37 2.0 f 1.35 9.56 + 2.50 0.02 + 0.01 59.01
39.82* 26.61 5.43k2.91 1.70+0.!34 7.86 + 0.54 0.03 i 0.01 47.96
83.29? 18.31 15.98k4.31 3.60& 1.52 7.45 + 1.10 0.044 k 0.004
C,,,( wg/ml) T,,, (h) MRT (h) 10
(h)
K,, (h-l) Rel. bioavailability (%I
Fig. 2. Effect of sodium carboxymethylcellulose concentration on the release of diclofenac sodium (X &SD> from beads in 0.1 N HCl and in phosphate buffer solution.
drug was slowly released from aluminum carboxymethylcellulose beads due to their slow disintegration (Table 1). The release of diclofenac sodium from the commercial Voltaren Retard tablets was the slowest as it released about 72% of the drug content in 10 h of dissolution. The concentration of the polymer used in the preparation of beads was found to affect the drug release. The dissolution results in Figs. 1 and 2 show that the higher the polymer concentration, the slower was the rate of drug release. Fig. 3 shows the mean (X + SEM) plasma-concentration time profiles of diclofenac sodium that resulted after oral administration of either aluminum-CMC beads, aluminum alginate beads or the commercial Voltaren Retard tablets to each of the five beagle dogs. The results show that the absorption of diclofenac sodium was fast as it appears in plasma samples withdrawn after 0.5 h in all
0
4
8
12
16
20
24
Time fh)
Fig. 3. Plasma concentration (X &SEMI of diclofenac sodium after oral administration of aluminum-CMC and aluminum alginate beads and the commercial Voltaren Retard tablets to five beagle dogs.
dogs from both formulations and the commercial tablets. It reaches C,,, within l-4 h in case of aluminum alginate beads with a mean T,,, of 2.0 + 1.35 h and a C,,, of 7.0 If: 1.37 pug/ml. While after administration of aluminum-CMC beads the C,,, was reached within l-3 h with a mean T,,, of 1.7 + 0.84 h and a C,,, of 5.43 + 2.91 pg/ml. While the commercial Voltaren Retard tablets showed a C,,, of 15.98 f 4.31 pg/ml within 2-6 h after administration with a mean T,,, of 3.6 + 1.52 h. The two beads formulations were non-significantly different (P > 0.05) with regards to C,,, , T,,, , AUC and plasma concentrations. Table 2 shows that the two formulations were also bioequivalent to each other where the aluminum alginate beads gave an area under the plasma concentration-time curve up to the last measurable concentration (AUC, _ 24h) of 48.99 + 11.07 pg h/ml compared to aluminum-CMC beads that gave an AUC0_24b of 39.82 + 26.61 pg h/ml. The two formulations showed a sustained plasma levels for the time of study i.e. for 24 h. The variations in AUCs were greater between dogs on administration of the aluminum-CMC beads than after administration of the alginate ones, showing coefficient of variations of 65.14 and 19.57%, respectively. While the coefficient of variations after administration of Voltaren tablets was 22.06%. The apparent elimination rate constants calculated by the least-squares regression analysis were 0.02 + 0.01, 0.03 + 0.01 and 0.04 + 0.00 h-’ for the aluminum alginate beads, aluminum-CMC-beads and commercial Voltaren Retard tablets, respectively. These formulations resulted in an MRT of 9.56 + 2.50, 7.86 & 0.54 and 7.45 f 1.10 h, respectively. These values show that the prepared beads are non-significantly different ( p > 0.05) from the commercial tablets with respect to their residence time of the drug in the body and even producing a non-significantly prolonged effect more than that of the commercial tablets.
164
E.A. Hosny et al./Pharmaceutica
In conclusion, based on both the in-vitro and in-vivo data the two polymers (NaCMC and Na-alginate) were able to form S.R. beads, and the resulting S.R. formulations of diclofenac sodium in the form of aluminum alginate or aluminum-CMC beads showed a relative bioavailability of 59.01 and 47.96%, respectively, compared to that of the commercial Voltaren Retard tablets of Ciba-Geigy which showed an AUC of 83.02 k 18.31 Fg h/ml.
References Alderman, D.A., 1984. A Review of cellulose ethers in hydrophilic matrices for oral controlled-release dosage forms. Int. J. Pharm. Tech. Prod. Manufact. 5, l-9. Bodmeier, R., Paeratakul, O., 1989. Spherical agglomerates of water-insoluble drugs. J. Pharm. Sci. 78, 964-967. El-Sayed, Y.M., Abdel-Hamid, M.E., Suleiman, M.S., Najib, N.M., 1988. A rapid and sensitive high-performance liquid chromatographic method for the determination of diclofenac sodium in serum and its use in pharmacokinetic studies. J. Pharm. Pharmacol. 40, 727-729. Hogan, J.E., 1989. Hydroxypropylmethylcellulose sustained-release technology Drug Dev. Ind. Pharm. 15, 975-1000. Langer, R.S., Peppas, N.A., 1987. Present and future applications of biomaterials in controlled drug delivery. Biomaterials 2, 201-214. McGinity, J.W., Harris, M.R., Dusch, R., 1986. In: Handbook of Pharmaceutical Excipients. American Pharmaceutical Association, Washington, DC, p. 5.
Acta Helvetiae 72 (1997) 159-164 Nishihata, T., 1987. Simple formulation of sustained-release tablets of sodium diclofenac and examination in humans. Int. J. Pharm. 40, 1255128. Nishihata, T., Wada, H., Kamada, A., 1985. Sustained-release of sodium diclofenac from suppository. Int. Pharm. 27, 245-253. Nishihata, T., Hirotani, Y., Yamazi, A., Takahashi, K., Yoshitomo, H., 1988. Preliminary study on sustained-release particles prepared with hydrogenated soya phospholipid and cholesterol. Int. J. Pharm. 42, 257-260. Ranga Rao, K.V., Padmalatha Devi, K., 1988. Swelling controlled-release systems: Recent development and applicants. Int. J. Pharm. 48, 1- 13. Reynolds, R.H.F., ‘Martindale’ The Extra Pharmacopoeia, 29th ed. The Pharmaceutical Press, London, 1989, p. 250. Rubio, M.R., Ghaly, ES., 1994. In-vitro release of acetaminophen from sodium alginate controlled release pellets. Drug Dev. Ind. Pharm. 20, 1239-1251. Simon, L.D., Ruiz-Cardona, L., Topp, E.M., Stella, V.J., 1994. Effect of pH on theophylline release from partially esterified alginic acid matrices. Drug Dev. Ind. Pharm. 20, 2341-2351. Takenaka, H., Kamashima, Y., Lin, S.Y., 1980. Micromeritic properties of sulfamethoxazole microcapsules prepared by gelatin acacia coacervation. J. Pharm. Sci. 69, 513-516. Thanoo, C.B., Sunny, C.M., Jayakrishnan, A., 1992. Cross-linked chitosan microspheres: Preparation and evaluation as a matrix for the controlled release of pharmaceuticals. J. Pharm. Pharmacol. 44, 283286. Valentina, I., Gilberto, G., 1995. Bead coating process via an excess of crosslinking agent. Drug Dev. Ind. Pharm. 21, 2307-2322.