Apparent Respiration Rate of the Human Corneal Epithelium with Tetracaine HCI and Benoxinate HCI

Local anesthetics may have a cytotoxic effect which causes a depression in the apparent epithelial oxygen uptake rate (AEOR) of the cornea. We measured the AEOR of human corneas in vivo before and after applying 1% tetracaine (amethocaine) HCI and 0.4% benoxinate HCI. These drugs had no effect on AEOR. In human corneas that had been subjected to a period of hypoxia, AEOR was slightly higher after administration of benoxinate, a result in the opposite direction to that expected on the grounds of toxicity. The increase was not statistically significant. We conclude that clinical doses of tetracaine HCI and benoxinate HCI normally have a minimal cytotoxic effect, and that this is similarly true when benoxinate is applied to the cornea after contact lens wear.