Stability of ceftazidime in a viscous eye drop formulation

To assess the stability of an extemporaneously prepared ceftazidime eye-drop.

Ceftazidime was formulated at a concentration of 5% w/v as an eye drop, using Sno Tears, an artificial tear solution containing polyvinyl alcohol, as a vehicle. Two batches of the formulation were stored in 10 ml eye drop bottles at 7 and 25 degrees C for up to 14 days. Ceftazidime and pyridine, its degradation product, were determined at intervals by HPLC.

A yellow coloration was evident after 7 days at 7 degrees C and after 24 h at 25 degrees C. Ceftazidime lost approximately 35% after 7 days storage at 25 degrees C. At 7 degrees C, the mean time to 10% degradation, determined by linear regression, was 11 and 8 days for the two batches. However, the lower 95% confidence limits were 8 and 5 days, respectively. Pyridine levels increased during storage. The mass balance between ceftazidime remaining and pyridine formed was close to 100% during the early part of storage. By the end of storage, the balance had reduced to around 95% at 7 degrees C and 80% at 25 degrees C. This discrepancy may be due to sorption of pyridine to the butyl rubber bottle closure. The pH remained in the range 6-7 throughout the storage period.

The formulation may be stored for 5 days in the refrigerator.