Stability of bendrofluazide in a low-dose extemporaneously prepared capsule

The stability of bendrofluazide 1.25 mg in capsules was studied. The formulation is intended to provide a unit dose powder for administration by dispersing the contents in liquid. The capsules were prepared from ground bendrofluazide tablets 5 mg from two different manufacturers, diluted with lactose and packed manually by weight into hard gelatin capsule shells. The capsules were stored at ambient temperature exposed to light or 75% relative humidity, and at 45 or 60C. The ambient temperature and 60C conditions were studied for up to 1 year. Bendrofluazide was determined by a stability-indicating HPLC method. The capsule contents remained easy to disperse in liquid by the end of the study. The weight of contents which could be extracted from the capsules also remained satisfactory. A 7-month storage life at ambient temperature would be feasible, based on the lower 95% confidence limits of the time to 5% degradation.