Benzalkonium chloride in glaucoma medications.

Benzalkonium chloride (BAK) is the preservative used most commonly in eye drops. Although it is effective as an antimicrobial and antifungal agent, both in vitro and in vivo studies have demonstrated adverse effects on surface epithelial cell populations. This is of particular concern with regard to topical medications used over long periods for chronic conditions, such as glaucoma. Newer non-BAK-containing drops are becoming increasingly available, providing an alternative for patients needing long-term eye drop therapy.