'The insertion cell': A novel approach to monitor drug release from semi-solid dosage forms

The flow-through cell for use in dissolution rate testing of solid dosage forms has recently become an additional compendial method in both the British Pharmacopoeia (Apparatus 3) and in the United States Pharmacopeia (Apparatus 4). Although none of the official dissolution methods have been specified for use with semi-solid dosage forms, their utility for assessing release rates of drugs from semi-solid dosage forms has become a topic of considerable interest. A custom-made insertion cell was constructed such that its dimensions permitted this cell to be used with the compendial flow-through cell. The release of acyclovir from two semi-solid dosage forms was monitored using this 'insertion cell' and the rank order of release was found to be in total agreement with previous data on the identical semi-solid dosage forms using previously described diffusion cells (Chattaraj et al., 1995; Chattaraj and Kanfer, 1995). The variability in the replicate data was, however, slightly greater when the %RSD values were compared to those previously obtained. These values, nevertheless, compare favourably with the results obtained using Franz diffusion cells. The 'insertion cell' offers distinct advantages compared to the Franz cells in that it is easier to use and readily adaptable for use with the compendial flow-through apparatus and does not suffer from the problem of having to remove air bubbles at the membrane/liquid interface, which commonly occurs when using Franz cells.