Drugs and the Eye

Abstract

It is possible to achieve a high concentration of many drugs in the eye by applying them as eye drops. In this way, a high local concentration can be reached with minimal risk of systemic side-effects. The systemic side-effects of drops can be underestimated. For example, one drop of timolol can slow the pulse rate and pilocarpine drops can cause sweating and nausea. The action of local applications may be prolonged by incorporating them in an ointment but for most purposes drops are supplied in 5 or 10 ml containers. After the container has been opened it should not be kept for longer than a month. In order to avoid undue stinging, drops may be buffered to near the pH of tears and they contain a preservative such as phenyl mercuric nitrate or benzalconium chloride. It must be kept in mind that patients who develop an allergic reaction to drops may be reacting to the preservative. Single application containers are also used which do not contain a preservative.