STABILITY OF ENALAPRIL MALEATE IN 3 EXTEMPORANEOUSLY PREPARED ORAL LIQUIDS

The stability of enalapril 1 mg/mL (as the maleate) in deionized water , citrate buffer solution, and a sweetened suspending agent at two tem peratures was studied. Twenty enalapril 10-mg tablets were crushed to a powder. Deionized water, citrate buffer solution, or sweetened vehic le was added to produce three 200-mL batches of each liquid; the expec ted final concentration of enalapril in each was 1 mg/mL. Each formula tion was stored in 10 60-mL, bottles, 5 of which were stored at 4 degr ees C and 5 at 25 degrees C. Samples were collected on days 0, 7, 14, 28, 42, 56, 70, and 91 for visual inspection and analysis by high-perf ormance liquid chromatography; pH was measured at each sampling time a s well. The mean concentration of enalapril in the three liquids at 4 degrees C was >94% of the initial concentration throughout the 91-day study period. At 25 degrees C, the mean concentration of enalapril was >90% for 56 days and >92% for 91 days in both citrate buffer solution and sweetened vehicle. The pH of the liquid prepared with deionized w ater and stored at 25 degrees C decreased by 2.0 pH units: Enalapril 1 mg/mL (as the maleate) in three extemporaneously compounded oral liqu ids was stable for 91 days at 4 and 25 degrees C with the exception of enalapril in deionized water, which was stable for only 56 days at 25 degrees C.