On the Maintenance of Sterility in Eye-Drops

Abstract

Conclusion and Summary A number of substances were tested against Ps. pyocyanea (Ps. œruginosa) and their bactericidal concentration determined. The quaternary ammonium compounds, although bactericidal, are not recommended because of their effect on the cornea. The mercurial compounds:—thiomersalate 0·005 per cent, and phenylmercuric acetate and nitrate 0·005 per cent., are safe, and are recommended for eserine and sodium fluorescein, which are the most liable to pyocyanea contamination, also for methylcellulose eye-drops, which are liable to contamination by moulds. These compounds are not only powerful bactericides but are also fungicides. Chlorbutol in saturated solution (about 0·8 per cent.) is safe and recommended, but owing to the fact that the solution cannot be heated without detriment to the preservative its use needs great care. Chlorcresol 0·1 per cent, is safe, but in that concentration it causes smarting, and 0·03 per cent, kills pyocyanea within 24 hours. The p-hydroxybenzoates in 0·1 per cent, solution are reliable for most of the eye-drops used except fluorescein. Phenylethyl alcohol is safe in 0·5 per cent, concentration but much quicker in its action at 0·6 per cent., and further clinical trials are needed with this promising preservative. For cortisone eye-drops 0·9 per cent, of benzyl alcohol, the one used in the original solution, is recommended. Eye-drops used in hospital wards, outpatient departments and factory medical rooms, should be prepared with bactericidal preservatives, but for eye-drops used by individual patients, a bacteriostatic agent may be permissible. However, for reasons of safety and to make it as foolproof as possible a uniform procedure using a bactericidal preservative is recommended. Up to now the National Formulary has recommended the use of bacteriostatic agents only. In view of the increasing incidence of eye infections reported by different authorities from many parts of the world, more stringent standards seem desirable.