Stability of Amlodipine Besylate in Two Liquid Dosage Forms

To determine the stability of amlodipine besylate in two liquid dosage forms under refrigeration and at room temperature. Commercially available amlodipine tablets (Norvasc-Pfizer) were used to prepare two suspensions: one in extemporaneously prepared 1% methylcellulose in syrup (1:1), and another in equal volumes of commercially available OraPlus/OraSweet. Each suspension containing amlodipine 1 mg/mL was stored in 10 plastic prescription bottles; 5 were stored at 4°C and 5 at 25°C. Samples were collected immediately after preparation (day 0) and on days 7, 14,28,42,56,70, and 91. Amlodipine concentration was measured by stability-indicating HPLC method (n = 15). Research laboratory at Children's Hospital. Physical and chemical stability (> 90% of the initial concentration) of amlodipine in the two extemporaneously prepared suspensions during storage in plastic prescription bottles at 4°C and 25°C. Observed mean concentrations exceeded 90% of the initial concentrations in both suspensions for 91 days at 4°C and 56 days at 25°C. No noticeable change in physical appearance or odor was observed; pH changed slightly in the methylcellulose-containing formulation stored at 25°C. Amlodipine was stable in two suspensions when stored in plastic prescription bottles for 91 days at 4°C or 56 days at 25°C. These formulations may be considered for pediatric or elderly patients who are unable to swallow tablets. The liquid dosage form would also permit accurate administration of amlodipine doses to infants and young children based on their body weight.