Hypokalemia associated with topical administration of dorzolamide 2% ophthalmic solution in cats.

Abstract

OBJECTIVE: To evaluate the effect of dorzolamide 2% ophthalmic solution on serum potassium and other hematologic parameters in cats. MATERIALS AND METHODS: Part I: Medical records from a single institution were retrospectively reviewed. Inclusion criteria consisted of cats diagnosed with glaucoma for which appropriate clinicopathological data were available both prior to and after the initiation of therapy with dorzolamide 2% ophthalmic solution. Part II: Healthy adult cats were enrolled in a prospective double-masked, randomized, cross-over study. Either dorzolamide 2% ophthalmic solution or placebo was administered OU t.i.d. for 6 weeks. Serum potassium, sodium, chloride, glucose, ALP, and ALT levels were assessed every 2 weeks. After a 2-week washout period, each cat was given the opposite topical preparation, and the study process was repeated. RESULTS: Part I: Of the twenty-seven eligible cases, hypokalemia developed in 29.6% (n = 8). While female spayed cats were significantly more likely to become hypokalemic, serum potassium was not significantly affected by age, weight, dosing frequency, or number of eyes treated. Part II: Ten cats participated in the study. Potassium values were significantly lower in cats receiving dorzolamide 2% ophthalmic solution compared to placebo at each time point throughout the 6-week study period. Additionally, chloride values were significantly greater in the treatment group at week two and four compared to the placebo group. CONCLUSIONS: Administration of dorzolamide 2% ophthalmic solution has a measurable effect on serum potassium level in cats and may result in clinical hypokalemia. Therefore, routine electrolyte monitoring is advised for feline patients receiving this medication.