Ocular penetration of subconjunctivally injected gentamicin, sisomicin and cephaloridine

The intraocular penetration of three current bactericidal broad-spectrum antibiotics, namely, gentamicin sulphate, sisomicin sulphate (Ensamycin) and cephaloridine, following subconjunctival injection was studied in 95 patients undergoing elective cataract surgery. Rapid and high penetration of all three drugs was evidenced by the fact that the first samples assayed by modified disc diffusion technique 15 minutes after injection showed drug levels effective against all susceptible pathogens. Peak levels of gentamicin, sisomicin and cephaloridine attained one hour after injection were 14.913 +/- 0.310, 19.000 +/- 0.408 and 30.830 +/- 1.195 micrograms/ml, respectively. Such high drug titres would provide drug concentrations 6 to 8 times the minimum inhibitory concentration necessary against susceptible organisms. The duration of the effective bioavailability of the drugs studied varied from 12 to 18 hours. We believe our study is the first to document the excellent penetration of sisomicin and the little-studied drug cephaloridine, and hope our results will open an avenue for in vivo studies to evaluate their clinical use.