To compare the in vitro toxicity of commercial olopatadine anti-allergic ophthalmic agents on cultured rabbit's conjunctival cells according to concentrations and exposure times. Methods

Rabbit conjunctival cells were exposed to anti-allergic olopatadine ophthalmic agents, (Patanol® [0.1% olopatadine hydrochloride; Alcon, Fort Worth, TX, USA], Pataday® [0.2% olopatadine hydrochloride; Alcon], and Pazeo® [0.7% olopatadine hydrochloride; Alcon]) at concentrations of 5%, 10%, and 15% for periods of 30 minutes, 1, 2, 3, and 6 hours, respectively. Cell proliferation and injury assays were performed using the methylthiazoltetrazolium and lactate dehydrogenase (LDH) leakage assays. We checked the composition of the three anti-allergic agents, and performed light and transmission electron microscopy to compare the morphological changes in cells. Results

The conjunctival cell proliferation was inhibited after 1 hour exposure to each olopatadine ophthalmic agent, with significant cell proliferation inhibited using 15% of each drug. The proliferation of conjunctival cells was inhibited during 6 hours of drug exposure at all concentrations of Pataday® and Pazeo®. The titer of LDH increased from 3 hours after drug exposure, but 15% Pazeo® significantly increased the LDH titer at 2 hours after drug exposure. As the concentration of the drug increased, the LDH titer also significantly increased. The cellular morphological changes of conjunctival cells were in the increasing order of Pazeo®, Pataday®, and Patanol® with a high concentration of olopatadine hydrochloride. Conclusions

Among the anti-allergic olopatidine ophthalmic agents, higher olopatadine concentrations in the increasing order of Pazeo®, Pataday®, and Patanol® resulted in cytoplasmic damage of conjunctival cells, but there was no severe damage to the cytoplasmic or the nuclear membranes.