Cyclosporine pharmacokinetics in cats following topical ocular administration

Topical ocular administration of two forms of cyclosporine were studied in the cat. Both forms were able to produce measurable whole-blood levels capable of suppressing in vitro lymphocyte stimulation. The kinetics of cyclosporine following administration of either oral solution or cyclosporine in olive oil were variable, with peak concentrations ranging from 450 to 1033 ng/ml and 288 to 648 ng/ml, respectively. Absorption lag time ranged from 0 to 1.34 hr for oral solution, and 0.27 to 1.2 hr for cyclosporine in olive oil. The half-life of elimination ranged from 2.41 to 10.04 hr, and 3.09 to 15.75 hr, respectively. When compared with the commercially available oral solution, cyclosporine dissolved in olive oil was better tolerated during administration. Topical ocular administration of cyclosporine in cats offers a possible alternative method of treatment for individuals intolerant of oral administration. Topical ocular administration might also replace the need for intravenous administration of cyclosporine during perioperative periods or during periods of vomiting and nausea associated with rejection or other illnesses. Due to individual variation in absorption and elimination of topically applied cyclosporine, dosages in each cat must be determined by monitoring blood, plasma, or serum levels.