Dissolution testing of soft shell capsules-acetaminophen and nifedipine

The problem of pelliculation of soft gelatin capsules on aging has been studied. Pelliculation frequently differs in soft shell capsules from hard shell capsules because of the larger mass of gelatin in the softshell dosage form. Two batches of nifedipine soft shell capsules are described. One batch failed in vivo testing and the other batch did not, after storage at 25 degrees C, yet both batches failed dissolution testing by the USP apparatus II method. The USP dissolution apparatus III-method, however, distinguished correctly between the batches. The study reported here was carried out with acetaminophen and was set up to establish whether the USP apparatus III testing method would be more suitable, and if so, what the most desirable dissolution medium should be. To create controlled pelliculation, samples were made with 0, 20, and 80 ppm of formaldehyde. The resulting capsules were subjected to ambient and accelerated storage and dissolution testing was carried out. It was found that the USP apparatus III method best reflected distinction between acceptable and substandard capsules.