Purpose:
The purpose of this study is to characterize the toxicity of non-preserved anti-glaucoma medications (latanoprost 0.005% and travoprost 0.004%; not commercially available), as well as the preservatives benzalkonium chloride (BAK) and boric acid (a major component of Sofzia) on human corneal epithelial (HCE) cells. Because the corneal epithelial cell line model is still in development, a pilot study was performed in a line of human retinal pigment epithelium (RPE) cells to validate the study techniques, which will be confirmed in the HCE cells.
Methods:
The hTERT-RPE line of human-derived RPE cells were grown in 96-well plates using standard culture methods. For testing the agents, the plate was divided into 9 groups of wells. One group (16 wells) served as a dead-cell control (70% ethanol). Two groups (8 wells each) served as live-cell controls (hydroxypropyl (HP)-Guar lubricant eyedrops 1:5 and 1:10). The other groups (n = #wells) were treated with travaprost 0.004% (16), latanoprost 0.005% (16), BAK 0.02% (8), BAK 0.005% (8), boric acid 0.1% (8), and boric acid 0.8% (8). Agents were diluted in culture media, and 200 µl were added to each well. Cells were incubated for 25 minutes at 37° C. The MTT cell viability assay was used to measure the effects of travaprost, latanoprost, BAK, and boric acid on the cells, compared to 70% ethanol and lubricant eyedrops.
Results:
Non-preserved latanoprost and travaprost showed no toxicity on the cells. BAK at 0.02% and 0.005%, and boric acid at 0.8% resulted in less than 5% viable cells. Boric acid at 0.1% resulted in ~60% viable cells. All of the preservatives significantly reduced viability compared to the non-preserved drugs (p<.001, Bonferroni multiple comparison).
Conclusions:
The toxic effects of glaucoma medications containing preservatives can be attributed solely to preservatives, as opposed to the medication's active ingredient. Medications preserved with boric acid may cause as much toxicity, depending on the concentration, as those preserved with BAK. Preservative-free glaucoma medications would be ideal for chronic topical use.
Keywords: ocular irritancy/toxicity testing • cell survival • cornea: epithelium