Enteral suspension of nifedipine for neonates. Part 2. Stability of an extemporaneously compounded nifedipine suspension

Objective: To investigate the chemical, microbiological and physical stability of an extemporaneously prepared nifedipine oral suspension, packaged in disposable syringes and prepared in a hospital pharmacy for paediatric use. Methods: Two different suspensions were prepared, from nifedipine tablets and drug powder, by using an autoclaved 1.0% solution of hypromellose as the vehicle. The final theoretical drug concentration was 1 mg/mL. Doses of 1.0 ml were packaged into a 2 ml syringe with a cap. Nifedipine suspensions were stored under three conditions: at room temperature (22 degreesC), in a refrigerator (6 degreesC) protected from light, and at room temperature (22 degreesC) exposed to artificial daylight (400 lux) under controlled circumstances. The nifedipine concentration was measured in suspensions protected from light on days 0, 1, 3, 5, 7, 14, 21 and 28, and in suspensions exposed to light at 0, 3, 6, 18 and 24 h, and on days 2, 3, 5 and 7 after preparation. Nifedipine was analysed by a reproducible and validated stability-indicating HPLC-method. Microbiological and physical stability of the nifedipine suspension samples protected from light were examined for 28 days. Results: Mean nifedipine concentration remained over 90% of the initial concentration throughout the 4-week study period in light-protected unit-dose suspensions, prepared from either crushed tablets or drug powder with hypromellose 1.0%. When exposed to light, however, nifedipine decomposed rapidly. Photodegradation of nifedipine exceeded 25% within 3 h and was essentially complete within 7 days. Conclusion: In the University Hospital of Kuopio, newborns have been treated with nifedipine suspension prepared from tablets, and preliminary experiences with administration of suspension have been encouraging. It may also be possible to apply this methodology to other medicines used in paediatrics.