Preservatives in eye drops. Myths and realities

Preservatives in eye drops are an important ingredient that helps prevent microbial contamination of the drug and allow it to be used in an open bottle for a long time. Quaternary ammonium compounds are most often used for the purposes in question — benzalkonium chloride, cetrimonium chloride, etc. Chlorobutanol, chlorhexidine, thimerosal, methylparaben, sodium perborate, etc. have also found application. Numerous studies indicate the effectiveness and relative safety of eye drops containing a preservative in an acceptable dosage. In addition, there is information about the ability of preservatives to increase the penetration of drugs into the eye. At the same time, a certain toxicity of the listed preservatives serves as a limitation to their widespread use, especially in patients with destructive corneal pathology, when wearing contact lenses, etc. In this regard, preservatives have been developed that have sufficient antimicrobial activity “in a bottle”, in the absence of toxicity for the tissues of the ocular surface, including due to their decay to biologically inert compounds in the conjunctival cavity (under  the influence of physical factors, enzymes of the lacrimal fluid, etc.): polyquad, oxide, purit, ocupur, SofZia, GenAqua, etc. A number of eye drops are now manufactured without preservatives at all (due to the special design of bottles or the use of single use dropper tubes). As clinical practice shows, preservative-free drugs are certainly preferable in the following situations: 1) the presence of dry eye syndrome in the patient or its development against the background of the use of drops with preservatives; 2) dystrophic or other diseases of the cornea or conjunctiva; 3) increased sensitivity of the ocular surface; 4) the need to wear soft contact lenses.