Release Studies of Neomycin From Different Ophthalmic Ointment Bases

Abstract

The release of neomycin from ten different ointment bases for possible ophthalmic use was monitored using a microbiological agar plate method. An obvious difference in antibiotic release from the various bases was observed. The effect of benzalkonium chloride, as preservative, on the antimicrobial activity of neomycin was studied and found to be dependent on the base used. From the whole set of results for release and stability, after shelf storage for 24 months, Bases No. 9 (containing castor oil, hydrogenated castor oil and cetyl alcohol) and No. 10 (containing liquid paraffin, hard paraffin, glyceryl monostearate and wool fat) were found to be the bases of choice for neomycin ophthalmic ointments.