Ocular and Systemic Pharmacokinetics of Lotilaner Ophthalmic Solution, 0.25%, Following a Single Dose or Repeated Doses in Dutch-Belted Rabbits

<b><i>Purpose:</i></b> To evaluate the ocular and systemic pharmacokinetics of lotilaner ophthalmic solution, 0.25%, following bilateral topical ocular administration of single and repeated doses in rabbits. <b><i>Methods:</i></b> Dutch-belted rabbits (<i>n</i> = 34) were administered lotilaner ophthalmic solution, 0.25%, eye drops, either in a single bilateral dose (Group 1) or twice a day bilaterally for 7 days and once on Day 8 (Group 2). The pharmacokinetics and tissue distribution levels of lotilaner were assessed following the single dose in Group 1 and the last dose in Group 2. The drug levels were examined in various ocular tissues and whole blood. The maximal concentration of the drug (Cmax), time to maximal concentration, the terminal phase elimination half-life, the area under the concentration-time curve (AUC), and total clearance of the drug were determined. <b><i>Results:</i></b> In the eyelid margins, lotilaner exhibited the highest observed concentrations at 0.25 hour (h), presenting a mean Cmax of 14,600 ng/mL in Group 1 and 20,100 ng/mL in Group 2. The highest AUC was in the eyelid margin at 242,000 h×ng/mL in Group 1 and 535,000 h×ng/mL in Group 2. In the eyelid margin, the observed clearance rate (0.634 mL/h in single dose, 0.288 mL/h in repeat dose) was the slowest among all ocular tissues in both groups, with the longest half-life of 152 h (∼6.3 days) observed in the repeat dose group. <b><i>Conclusions:</i></b> Lotilaner ophthalmic solution, 0.25%, demonstrated rapid ocular tissue absorption into the eyelid margin tissue with a long half-life of almost a week. No adverse effects were observed following topical ocular administration in Dutch-belted rabbits.