Stability of pediatric liquid dosage forms of ethacrynic acid, indomethacin, methyldopate hydrochloride, prednisone and spironolactone

The stability of liquid dosage forms of ethacrynic acid (1 mg/ml), indomethacin (2 mg/ml), methyldopate hydrochloride (25 mg/ml), prednisone (0.5 mg/ml) and spironolactone (2 mg/ml), which often are compounded extemporaneously, was studied. One or two liquid dosage forms of each of the five drugs was prepared with the pure drug or the powder from a commercial dosage form using aqueous sorbitol or simple syrup alone or with a 10% (v/v) solution of alcohol in water. The dosage forms were stored at 24 C in amber-colored bottles for 21-224 days and assayed by various methods. All solutions studied were stable for at least 84 days. A solution was considered stable if it retained 90% of its drug concentration. Except for the prednisone solution, all solutions were stable for at least 164 days; however, the solution of methyldopate hydrochloride prepared from the pure drug became discolored after 98 days. The liquid dosage forms studied have limited stability but can be used by the pharmacist when extemporaneous oral solutions of these drugs are needed.