In-vitro Dissolution Study of Pharmaceutical Products with USP Apparatus- IV

The objective of the present article is to review various aspects of dissolution studies of dosage forms performed with the flow-through apparatus (USP type-IV apparatus). USP type-IV apparatus is comprised of a pump that compels the dissolution media upwards via the flow-through cell. A reservoir of dissolution medium is attached to the cell that is mounted vertically with a filter system to restrain the escape of un-dissolved particles. The apparatus is specially designed for powders, microparticles, pellets and tablets. In this type of in vitro dissolution method, the test sample is placed in the bottom of the small-volume flow-through cell; the solvent passes through it at a temperature of 37°C. This study is very important to build up the in-vivo and in-vitro relationship. Likewise, this study is used to distinguish the extent of medication released from the tested sample so as to foresee its in vivo viability in actual patient population. The flow-through cell is used to determine the dissolution of micro-particulate, suppositories, implants, controlled-release formulations with drugs that have very low aqueous solubility. The drugs with small particle size and large surface area are dissolved at a faster rate as compared to other existing and compendial dissolution apparatuses. The article also highlights some of the in vitro dissolution studies carried out with the USP type-IV apparatus.