P9 Mucoadhesive polymers polycarbophil and chitosan enhance peptide absorption

389 inhibit trypsin. Furthermore, under the same conditions, Carbopol@ 934P seems to be more potent than PolycarboPhil. The minimum inhibiting concentration is 0.1% (w/v). Additionally, it has been shown that the activity of the serine protease trypsin is Ca’+dependent [ 41. Because of the Ca’+-complexing properties of Polycarbophil and Carbopal@ 934P, degradation studies at pH 6.7 under addition of Ca*+ at different times were also performed. After addition of 14.3 mmol/l Ca*+ to both polymers before trypsin incubation, trypsin activity was not inhibited. The trypsin activity was partly recovered when CaZ+ was added after lo-min incubation, but not when Ca2+ was added after 240 min. The observation that the recovery of degradation activity is timedependent for Ca *+ addition, suggests that irreversible denaturation of trypsin occurs under the depletion of Ca*+ by the polymers with time. Moreover, other bioadhesive polymers, like chitosan-lactate, chitosan-glutamate, Gantrez” 119 AN and methylcellulose, were also investigated, but none of these compounds showed an inhibitory effect on trypsin activity. To exclude the possibility that the enzyme inhibition may contribute to an immobilization effect, due to the viscous properties of the polymer preparations, rheological measurements at 37°C were performed. From these results it was evident that no correlation exists between degradation activity of trypsin and viscosity. In contrast, in some preparations with a relatively high viscosity, like methylcellulose ( II w/v, 29.68 mPas) and chitosan-lactate (0.5% w/v, 11.86 mPas), compared to blank (Mes/KOH buffer, pH 6.7, 0.7 mPas), the degradation velocity had even increased. From these studies it is concluded that the two poly (acrylic acid) derivatives Polycarbophil and Carbopol” 934P are able to protect peptide drugs against proteolytic degradation by trypsin. The complex mechanism of action still remains to be investigated.

University,P.O. Box 9502, 2300 RA Leiden, The Netherlands As previously reported [ 1] the transport of small peptides across the rat intestinal tissue in vitro and in vivo was significantly increased under the influence of the mucoadhesive polymer polycarbophil (PCP ) . The aim of this study was to evaluate the potential of another, positively charged mucoadhesive polymer, such as chitosan ( l-4)-2-amino-2-deoxy-&D-glucan) to enhance the intestinal absorption of peptide drugs under the same experimental conditions in vitro. In an in vitro experiment with isolated gut of male Wistar rats, administration of 5.0 ml of a lo/o (m/V) PCP-suspension containing lO,~g DGAVP led to significantly higher concentrations in the acceptor compartment in comparison to the same dose without PCP. The same held also for the 1% (m/V) chitosan and chitosan glutamate suspensions. The 0.4% (m/V) chitosan glutamate dispersion showed an effect comparable with the 1% dispersions of free chitosan or PCP respectively. In contrast, a 0.4W preparation of chitosan did not enhance intestinal absorption in comparison to the control experiment. Chitosan (glutamate) concentrations of 2% (m/V) and higher could not be investigated in this model due to their extremely high viscosity. The viscosity data are not correlated to the observed enhanced peptide absorption, suggesting that the effects are not simply explicable by increased viscosity. In contrast to polycarbophil, which is a potent enzyme inhibitor [ 2 1, the enzyme activity kinetics of trypsin showed no inhibition by chitosan glutamate. Conclusion: Chitosan and chitosan glutamate enhanced the intestinal absorption of a peptide drug in vitro. In comparison to chitosan, chitosan glutamate was found to be more potent. The penetration enhancement by chitosan glutamate cannot be ascribed to enzyme inhibition or increased viscosity.

References References 1 C.-M. Lehr, J.A. Bouwstra, W. Kok, A.G. de Boer, J.J. Tukker, J.C. Verhoef, D.D. Breimer, H.E. Junginger, Effects of the mucoadhesive polymer polycarbophil on the intestinal absorption of a peptide drug in the rat, J. Pharm. Pharmacol., 44 ( 1992) 402-407. 2 C.-M. Lehr, Bioadhesive drug delivery systems for oral application, thesis, Leiden, 199 1. 3 H.L. LueDen, J.C. Verhoef, A.G. de Boer, H.E. Junginger, Studies of trypsin inhibition by pharmaceutical excipients with bioadhesive properties, Pharm. Weekbl., Sci. Edn., Suppl. F, 14 (1992) 69. 4 R.J. Beynon, J.S. Bond, Proteolytic enzymes, IRL Press, Oxford, 1990. P!J Mucoadhesive polymers polycarbophil and cbitosan enhance peptide absorption. C.-O. Rentel, C.-M. Lehr, J.A. Bouwstra, H.L. LueBen and H.E. Junginger, Leiden/Amsterdam Center for Drug Research, Division of Pharmaceutical Technology, Center for Bio-Pharmaceutical Sciences, Leiden

1 C.-M. Lehr, J.A. Bouwstra, W. Kok, A.G. de Boer, J.J. Tukker, J.C. Verhoef, D.D. Breimer and H.E. Junginger, J. Pharm. Pharmacol., 44 ( 1992) 402-407. 2 H.L. LueBen, C.-M. Lehr, J.C. Verhoef A.G. de Boer and H.E. Junginger, Derivatives of poly(acrylic acid) influence the degradation activity of the proteolytic enzyme trypsin, Proc. Int. Symp. Controlled Release Bioact. Mater., 20 (1993) 268-269. PI0 Effects of experimentally induced colitis on rat intestinal permeability to ovalbumin and “Cr-EDTA in vitro. B.R. Westroma, N. Pantzal-8, Q. Wang”, G. Ekstriimb, P. Lundin” and B. Karlsson”, “Lund University,Department ofAnimal Physiology, Helgonaviigen 3B, S-223 62 Lund, Sweden; bAstra Draco, Box 34, S-221 00 Lund, Sweden Background: The effect of an experimentally induced colitic inflammation on the intestinal permeability was studied in different parts of the gut, by incubating intestinal segments