Aqueous humor and serum penetration of tacrolimus after topical and oral administration in rats: an absorption study

PURPOSE: To investigate the penetration of tacrolimus to the aqueous and serum after topical and oral administration. METHODS: Thirty Wistar rats were divided into three groups. In the first group (n = 12), a single dose of 0.3 % isotonic tacrolimus solution was applied topically to the rat eyes. The second group (n = 12), received 0.1 mg/kg/day tacrolimus for three days. In control group (n = 6), the rats were administered a single drop of 0.3% salin solution topically. Following collection of samples, the amounts of tacrolimus in aqueous and serum samples were compared with each other. RESULTS: In group I, the mean concentration of tacrolimus was 35.16 ng/ml in aqueous and 2.22 ng/ml in serum. In group II, the mean concentration of tacrolimus was 13.08 ng/ml in aqueous and 13.45 ng/ml in serum. There was no significant difference in the serum concentration levels of tacrolimus between group I and control group. However there was a significant difference of the drug concentrations in aqueous between the groups (p < 0.001). The mean aqueous and serum concentrations of tacrolimus in group II, differed significantly from the mean concentrations in group I (p < 0.001) and the control group (p < 0.001). CONCLUSION: Tacrolimus may be a promising treatment modality in intraocular inflammation by topical application besides systemic administration.