Phillips, D. J., Pygall, Samuel R., Cooper, V. Brett and Mann, James C.. (2012) Overcoming sink limitations in dissolution testing : a review of traditional methods and the potential utility of biphasic systems. Journal of Pharmacy and Pharmacology, Vol.64 (No.11). pp. 1549-1559. ISSN 0022-3573

Abstract

Objectives The conventional dissolution test, particularly the USP apparatus I and II, remains an important tool in the armory of the pharmaceutical development scientist. For realistic dissolution characterization, sink conditions, where saturation solubility of a drug in the dissolution medium is at least three times more than the drug concentration, are critical. These conditions can be problematic to maintain with formulations containing poorly-soluble actives. This review summarizes the role of the dissolution test in the pharmaceutical industry, together with some traditional techniques/additives used to enhance solubility and facilitate the achievement of sink conditions. The biphasic dissolution system, an innovative model for the treatment of poorly-soluble species, will also be discussed. Key findings The biphasic dissolution model utilizes media comprising immiscible aqueous and organic layers whereby the drug, following initial aqueous dissolution, partitions into the organic layer. This step, which acts to remove all dissolved species from the aqueous layer, enables further aqueous dissolution to occur and hence the dissolution-partition cycle continues. Crucially, the aqueous layer does not saturate allowing sink conditions to be maintained and hence the experiment will, in theory, yield complete dissolution. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

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