Antiglaucoma drugs: The role of preservative-free formulations

Hypersensitive reactions to eyedrops are a common finding in clinical practice and represent a frequent cause of discontinuation of the therapy. Moreover, experimental and clinical studies show that long term use of topical drugs may induce ocular surface changes causing discomfort and potentially negatively affecting the compliance to the treatment as well as the success rate of filtering procedures. The exact mechanism involved and the roles of the active compound and the preservatives in inducing such detrimental effects of ophthalmic solutions are unclear. During the last years several antiglaucoma agents have been marketed as either preservative-free or benzalkonium chloride-free formulations in an attempt to reduce the adverse effects related to preservatives. This paper summarizes the body of evidence from existing studies about preservatives in antiglaucoma eyedrops, focusing on the latest compounds commercially available. A systematic review of the literature was performed. Current research is focusing not only on the efficacy of the drugs but also on their tolerability. Based on the existing data, there is a rationale to support the use of benzalkonium-free solutions whenever possible, especially in patients suffering from concomitant ocular surface diseases, experiencing local side effects and in those expected to need multiple and prolonged topical treatments.