Preservatives in topical ophthalmic medications: historical and clinical perspectives

Patients may be subject to a variety of different topical medications when undergoing treatment for ocular disease. Preservatives are added to multidose medication bottles to inhibit microbial contamination. An assortment of different preservative formulations has been used in ophthalmic medicines and many of these preservatives have been linked to unwanted ocular surface side effects. Benzalkonium chloride in particular has been linked to a number of different adverse effects, such as disruption of the tear film as well as damage to ocular surface epithelial cells. As a result, the manufacturers of ocular medications have developed innovative new preservative systems in an attempt to limit these toxic side effects. This article reviews the different ophthalmic preservative formulations, their benefits, detriments, mechanisms of action and historical aspects. Future prospects and clinical objectives with regard to ophthalmic preservatives are also discussed.