Stability of amiodarone in an oral suspension stored under refrigeration and at room temperature

OBJECTIVE: Amiodarone is currently available in a tablet dosage form, which cannot be used in young pediatric patients. The objective of our study was to determine the stability of amiodarone in an oral suspension stored at two temperatures. METHODS: Commercially available amiodarone tablets (200 mg each) were dissolved in purified water and a suspension prepared in methylcellulose 1% and syrup to yield a concentration of 5 mg/mL. The dosage form was stored in 10 glass and 10 plastic prescription bottles. One-half of the bottles were stored at 4 degrees C and the others at 25 degrees C. Three samples were taken from each bottle at 0, 7, 14, 28, 42, 56, 70, and 91 days (n = 15). Amiodarone concentrations were measured by a validated and stability-indicating HPLC method; the pH was also determined in each sample. The drug was considered stable if its concentration exceeded 90% of the original concentration. RESULTS: The mean concentration of amiodarone was 90% or more at 4 degrees C for 91 days and at 25 degrees C for 42 days. The concentration was not affected by the type of storage container. Over 91 days, the pH did not change at 4 degrees C; it decreased slightly from 4.4 to 4.3 at 25 degrees C. CONCLUSIONS: Amiodarone was stable in an oral suspension for 3 months under refrigeration and for 6 weeks at room temperature.