Plasma Pharmacokinetics of Topical 0.1% Diclofenac Sodium and 0.5% Ketorolac Tromethamine in Dogs.

Topical ketorolac achieves six times greater systemic exposure than diclofenac in dogs.

This prospective, randomized, crossover study evaluated plasma pharmacokinetics of two topical ophthalmic nonsteroidal anti-inflammatory drugs in eight healthy Beagles. Dogs received 0.05 mL of either 0.1% diclofenac sodium or 0.5% ketorolac tromethamine instilled into both eyes four times daily for five days. Plasma samples were collected at multiple timepoints on days 1 and 5 following the final dose. Both drugs demonstrated rapid systemic absorption after topical ocular administration. Diclofenac achieved peak plasma concentrations of 0.12 ± 0.05 μg/mL at 3.08 ± 0.9 hours with an AUC of 8.97 ± 3.73 μg/mL*h. Ketorolac reached higher peak concentrations of 1.8 ± 1.7 μg/mL, though delayed to 18.5 ± 14.6 hours, with significantly higher AUC of 98.2 ± 43.3 μg/mL*h. Both drugs exhibited similar half-lives of approximately 121 hours. These findings indicate that ketorolac achieves substantially greater systemic exposure than diclofenac when administered topically, with potential clinical implications for drug selection and dosing intervals in veterinary ophthalmology.

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