The stability of famotidine in an extemporaneously prepared oral liquid stored at 4 and 24 degrees C for 30 days was studied. Famotidine liquid was prepared by pulverizing and suspending 12 40-mg tablets in distilled water. This mixture was diluted with cherry syrup to a total volume of 60 mL, resulting in a famotidine concentration of 8 mg/mL. The liquid was divided into two 30-mL amber glass bottles and stored at 4 degrees C and at room temperature (24 degrees C). Samples from each of the two bottles were assayed for famotidine content by high-performance liquid chromatography. Each sample was assayed in duplicate at time 0 and on days 2, 5, 10, 15, 20, 25 and 30. The concentration of famotidine remained above 90% of original concentration for 20 days at 4 degrees C and for 15 days at room temperature. After 30 days, famotidine concentration was reduced by 15% and 24% at 4 degrees C and room temperature respectively. Famotidine liquid 8 mg/mL compounded extemporaneously from tablets was stable for 20 days at 4 degrees C and for 15 days at 24 degrees C.