BACKGROUND: Lisinopril is used in pediatric patients with hypertension. It is not commercially available as a liquid. Little is known about the stability of lisinopril in extemporaneously prepared liquid dosage forms. OBJECTIVE: To determine the stability of lisinopril in 2 oral suspensions stored at 4 and 25 degrees C in plastic prescription bottles. METHODS: Five bottles contained methylcellulose 1%:simple syrup NF (1:13) and the other 5 bottles had Ora Plus-Ora Sweet (1:1) at a lisinopril concentration of 1 mg/mL. Three samples were collected from each bottle at 0, 7, 14, 28, 42, 56, 70, and 91 days and analyzed by stability-indicating HPLC analytical method (n = 15). RESULTS: At 4 degrees C, the mean +/- SD concentration of lisinopril remained >95.1 +/- 1.8% of the initial concentration in the methylcellulose formulation and 95.1 +/- 3.2% of the initial concentration in the Ora Plus-Ora Sweet formulation throughout the 91-day study period. At 25 degrees C, the mean concentration of lisinopril remained >92.4 +/- 2.2% of the initial concentration in the methylcellulose formulation for 8 weeks and 95.8 +/- 2.3% of the initial concentration in the Ora Plus-Ora Sweet formulation throughout the 91-day study period. No changes in physical appearance in any samples were seen during this period. CONCLUSIONS: Lisinopril can be prepared in either of 2 liquid dosage forms and stored for at least 13 weeks under refrigeration and 8 weeks at room temperature.