Quality control of capsules

The evaluation of capsules, in general, follows the line for compressed tablets and tests like the weight variations test, content uniformity test, disintegration and dissolution time.

Weight variation : 

This test is done by taking 20 capsules individually, determining average weight per capsule and finding out weight variation of each capsule against the average value(± 10% variations are permitted). However, if the variations are beyond this limit net weight of contents of each capsule should be determined, and compared with average net weight. This will remove any doubt about the possible variation in the weights of individual shells. As per standards specified in some Pharmacopoeias net weight of not more than two capsules should differ by more than ± 10% from the average net weight and no capsule should differ by more than ± 25%. If the average net weights of 2 to 6 capsules deviate by ± 10 to 25%, net weights of 40 more capsules should be determined. In a total of 60 capsules not more than six should deviate from average by more than ± 10% and none by more than ±25%.

Disintegration and dissolution time :

 Capsules are not normally tested for disintegration as their shells are known to dissolve rapidly in the gastric fluids. However, capsules which are designed to be enteric, by treatment of their shells with formaldehyde, should be tested thus to ensure than they do not disintegrate in simulated gastric juice under simulated conditions. Dissolution time tests are run on the lines of compressed tablets. Any of the standard apparatus available for dissolution tests can be employed. The determination of dissolution time is important since absorption of drugs depends upon their dissolution times.

Drug content uniformity :

 In solid dosage forms uniform distribution of medicaments remains a problem. The problem becomes more acute with potent medicaments administered in low doses. Hence, a number of capsules should be selected and assayed for drug content individually. Pharmacopoeias specify 30 capsules out of which 10 should be assayed individually in the first instance. Out of these at least 9 should be within ±15% of average and none should be beyond ±25. If 1 to 3 capsules out of the 10 assayed originally fall outside ±15% the remaining 20 should be assayed. Out of the total 30 capsules at least 27 should be within ±15% and no capsule should be beyond ±25%.