Topical versus intravenous administration of tranexamic acid: A comparison of intraocular and serum concentrations in the rabbit

Background: Tranexamic acid has been shown to greatly reduce the incidence of secondary hemorrhage when administered orally or intravenously. Topical administration of the drug should result in much lower serum concentrations, with fewer adverse effects. We performed a study to determine whether topical application of tranexamic acid would yield higher intraocular concentrations and lower serum concentrations of drug than intravenous administration. Methods: Ten New Zealand white rabbits received 25 mg/kg of tranexamic acid intravenously every 8 hours for 3 days. Another group of 10 rabbits received one drop (0.05 mL) of commercially available tranexamic acid solution (100 ng/mL) every 8 hours for 3 days to one eye. Tranexamic acid levels in the aqueous humour, vitreous humour and serum I hour after administration of the last dose of drug were determined. Results: Analysis of variance showed that aqueous concentrations of tranexamic acid were significantly higher with topical delivery than with intravenous administration (15 vs. 9 μg/mL) (p < 0.05). Serum concentrations were significantly lower following topical administration (9 vs. 19 μg/mL) (p < 0.01). The drug was not detected in the vitreous humour in either group. Interpretation: Topical delivery of tranexamic acid may prove to be valiable in yielding therapeutic intraocular concentrations of drug in patients with hyphema while minimizing systemic toxicity.