Evolution of a physiological pH6.8 bicarbonate buffer system: Application to the dissolution testing of enteric coated products.

Liu, F., Merchant, H.A., Kulkarni, R.P., Alkademi, M. and Basit, A.W. (2011) Evolution of a physiological pH6.8 bicarbonate buffer system: Application to the dissolution testing of enteric coated products. European Journal of Pharmaceutics and Biopharmaceutics, 78 (1). pp. 151-157. 10.1016/j.ejpb.2011.01.001 .

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DOI: 10.1016/j.ejpb.2011.01.001

Abstract

The use of compendial pH6.8 phosphate buffer to assess dissolution of enteric coated products gives rise to poor in vitro-in vivo correlations because of the inadequacy of the buffer to resemble small intestinal fluids. A more representative and physiological medium, pH6.8 bicarbonate buffer, was developed to evaluate the dissolution behaviour of enteric coatings. The bicarbonate system was evolved from pH7.4 Hanks balanced salt solution to produce a pH6.8 bicarbonate buffer (modified Hanks buffer, mHanks), which resembles the ionic composition and buffer capacity of intestinal milieu. Prednisolone tablets were coated with a range of enteric polymers: hypromellose phthalate (HP-50 and HP-55), cellulose acetate phthalate (CAP), hypromellose acetate succinate (HPMCAS-LF and HPMCAS-MF), methacrylic acid copolymers (EUDRAGIT® L100-55, EUDRAGIT® L30D-55 and EUDRAGIT® L100) and polyvinyl acetate phthalate (PVAP). Dissolution of coated tablets was carried out using USP-II apparatus in 0.1M HCl for 2h followed by pH6.8 phosphate buffer or pH6.8 mHanks bicarbonate buffer. In pH6.8 phosphate buffer, the various enteric polymer coated products displayed rapid and comparable dissolution profiles. In pH6.8 mHanks buffer, drug release was delayed and marked differences were observed between the various coated tablets, which is comparable to the delayed disintegration times reported in the literature for enteric coated products in the human small intestine. In summary, the use of pH6.8 physiological bicarbonate buffer (mHanks) provides more realistic and discriminative in vitro release assessment of enteric coated formulations compared to compendial phosphate buffer.

Item Type:Article
Departments, units and centres:Department of Pharmaceutics > Department of Pharmaceutics
ID Code:1822
Journal or Publication Title:European Journal of Pharmaceutics and Biopharmaceutics
Deposited By:Library Staff
Deposited On:27 Feb 2011 18:03
Last Modified:19 May 2011 11:06

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