The Effect of Prostaglandin Ocular Hypertensive Analogue Formulations and Their Components on the Ocular Surface (Corneal and Conjunctival Epithelium)

Abstract

Purpose: : Prostaglandin Ocular Hypertensive Analogues (POHAs) are the most common medical treatment for glaucoma. POHA formulations contain preservatives to limit bacterial contamination. To evaluate the potential toxicity of each of the compounds to the ocular surface, a tissue culture model utilizing immortalized corneal and conjunctival epithelial cells was utilized.

Methods: : Immortalized human conjunctival cells (Chang's P61 Conjunctival Cells) and corneal epithelial cells (CEPI 17) were obtained and seeded at 10³ cells/well and kept at 37^oC, 5% CO₂. At confluency, media in all wells was arbitrarily replaced with 100 uls of the commercially marketed POHA formulations and their major constituents: Lumigan^TM, bimatoprost 0.03%, benzalkonium chloride (BAK) 0.05%, PBS; Xalatan^TM, latanoprost 0.005%, BAK 0.02%, PBS; and Travatan^TM, travaprost 0.004%, BAK 0.015%, Disodium–Ethylene Diamine Tetra–Acetate (EDTA); as well as viable (pure cell media) and dead (formalin) controls. After 1 hour, the solution was removed and 150 uls of MTT (3–[4,5–dimethylthiazol–2–yl]–2,5–diphenyl tetrazonium bromide) was added to each well for 4 hours at 37^oC. After decanting, 100 uls of acid isopropanol was added. The absorbance of each was then determined at 572 nm and equated, relative to the controls, with "viability", and conversely, "toxicity".

Results: : The active agents of all tested commercial POHA formulations were more toxic than controls and buffers [bimatoprost: 44.62% (Chang's: 47.17%±22.08, HCE: 42.07%±32.58); latanoprost: 43.86% (Chang's: 47.55%±19.77, HCE: 40.16%±38.05); travaprost: 36.59% (Chang's: 36.96%±22.00, HCE: 36.21%±32.93)]. The preservative BAK demonstrated the majority of the toxicity exhibited by the commercial POHA formulations (Lumigan^TM: ≈65%, Xalatan^TM: ≈64%, and Travatan^TM: ≈68% of the observed toxicity). All tested preservatives behaved in dose dependent manner and proved more toxic than the active agent and less toxic than the commercial formulations.

Conclusions: : Preservatives proved to exhibit the majority of the toxicity exhibited by the commercial POHAs: Lumigan > Xalatan > Travatan. All tested preservatives behaved in dose dependent manner and proved more toxic than the active agent and less toxic than the commercial formulations. Use of non–preserved POHAs may lead to less surface toxicity.

Keywords: drug toxicity/drug effects • ocular irritancy/toxicity testing • pharmacology