Effects of benzalkonium chloride- and polyquad-preserved combination glaucoma medications on cultured human ocular surface cells

The aim of this study is to investigate potential adverse effects of fixed combination glaucoma medications preserved with either benzalkonium chloride (BAK) or PolyquadA (R) (PQ; Alcon Research Ltd., Fort Worth, TX, USA) on cultured ocular epithelial cells. Confluent cultures of human cornea and conjunctival cell lines were exposed for 25 minutes to different glaucoma medications as well as a range of concentrations of BAK (0.001%-0.050%). Balanced salt solution was used as the live control and a solution containing 70% methanol and 0.2% saponin was used as a dead control. The number of dead and live cells were determined via ethidium homodimer (Eth-1) and calcein acetoxymethyl ester (AM) fluorescence, respectively. The toxicity of the prostaglandin analog with beta-blocker timolol fixed-combination formulations preserved with BAK was different from that observed in the respective BAK concentrations. Travoprost plus timolol fixed combination with BAK performed better than its respective BAK concentration alone, while the latanoprost plus timolol fixed combination performed worse than its respective BAK concentration. Travoprost plus timolol fixed combination preserved with PQ had greater corneal and conjunctival cell survival than either the travoprost plus timolol fixed combination preserved with BAK or the latanoprost plus timolol fixed combination. Ocular surface side effects have previously been demonstrated with chronic, long-term exposure to intraocular-pressure-lowering medications containing the common preservative BAK. BAK alone has significant in-vitro cytotoxicity to cultured ocular epithelial cells. Substitution of BAK with PQ resulted in significantly higher percentages of live conjunctival and corneal cells. Further studies are needed to understand the clinical implications of these findings.