In vitro biphasic dissolution tests and their suitability for establishing in vitro-in vivo correlations: A historical review

For many decades, one of the most critical issues in the pharmaceutical industry has been the poor solubility of some drugs. Indeed, a prerequisite for drug absorption is the presence of dissolved drug at the absorption site and this can be challenging for compounds with low aqueous solubility such as BCS class II (low solubility, high permeability) and IV (low solubility, low permeability) compounds. If the development of oral delivery formulations of these compounds is frequently challenging to formulation scientists in the pharmaceutical industry, the in vitro evaluation of these new formulations is also a great challenge. One alternative approach to overcome the problems encountered with conventional dissolution methods is the use of biphasic dissolution systems. This review provides an overview of the origin and the evolution over time of the biphasic systems and the growing interest among scientists regarding their suitability for establishing in vitro-in vivo correlations. The evolution of these systems and their applications from the 1960s to the present day, such as in system variants and improvements, analysis of complex formulations, discriminatory power, bio-relevance, precipitation and supersaturation visualization, etc. will be discussed