STABILITY OF CEFAZOLIN SODIUM EYE DROPS

Objective: Assessing the stability of cefazolin sodium in preservative -free and preservative-containing eye drops. Method: Extemporaneous fo rmulations of eye drops were prepared from a commercially-available pa renteral product of cefazolin sodium: eye drops 'A' contained 50 mg/ml of cefazolin sodium in 0.45% w/v sodium chloride solution, and eye dr ops 'B' contained 50 mg/ml, 0.005% w/v thiomersal and 1% w/v glycerol in water-for-injection. Cefazolin sodium concentrations in these eye d rops were monitored by a stability-indicating HPLC assay method. Measu rements of pH and osmolality, as well as tests for microbial contamina tion, were conducted. Results: The eye drops stored at 4 degrees C wer e stable for 42 days with minimal changes in pH and osmolality, but ey e drops stored at room temperature were only stable for a few days wit h greater increments in pH and osmolality. None of the samples culture d had bacterial or fungal growth after 7 days of incubation. Conclusio n: Extemporaneously prepared formulations of cefazolin are unstable at room temperature and should be stored in a refrigerator.