The Effects on Porcine Isolated Corneas of the Addition of Various Preservatives to Befunolol-HCl Solutions

Abstract

The opacity which develops in intact porcine isolated corneas during incubation for a period of four hours at 35°C with solutions of befunolol-HCl (5 x 10-4M, 5 x 10 -3M, 5 x 10-2M) is increased by the presence of benzalkonium chloride (BC; 0.005%) or a mixture of chlorobutanol (0.2%), methyl p-hydroxybenzoate (MPB; 0.026%) and propyl- p-hydroxybenzoate (PPB; 0.014%). The addition of BC had a greater effect than the addition of the chlorobutanol/ MPB/PPB mixture, when solutions were applied only to the epithelial surface, only to the endothelial surface, or to both surfaces simultaneously. However, when the individual constituents of the mixture were added separately to more-concentrated befunolol solutions (5 x 10-2M), chlorobutanol, MPB and PPB each increased opacity when solutions were applied only to the epithelial surface; MPB and PPB increased, but chlorobutanol decreased, opacity when solutions were applied only to the endothelial surface; and chlorobutanol increased, but MPB and PPB each decreased, opacity when solutions were applied to both surfaces. Assuming that BC and the mixture of chlorobutanol/MPB/PPB are equally effective as preservatives, the results suggest that the latter mixture may be preferable to BC in eye-drops intended for long-term use.