Keratoconjunctivitis sicca (KCS) is prevalent in dogs. Depending on the severity and duration of disease, it causes a wide range of clinical signs. Canine KCS has numerous causes, but the most common is probably immune-mediated dacryoadenitis. Topical cyclosporine A (CsA) is efficacious in the treatment of KCS, but a significant number of dogs do not respond to it. A new ascomycin derivative, pimecrolimus, with the same molecular mechanism of action as CsA has significant activity in animal models of immune-mediated inflammatory diseases, especially canine KCS. A multicenter outpatient clinical trial was performed to confirm the efficacy of this drug and compare it with the veterinary form of CsA. Forty-four dogs diagnosed with KCS and previously untreated with CsA were randomly assigned to receive treatment with 1% pimecrolimus ophthalmic formulation (n = 24) or 0.2% CsA (n = 20). Treatments were administered Q 12 H in both eyes for 8 weeks. Complete physical and ophthalmic examinations were performed on weeks 2, 4, and 8 of the study. Mean baseline values on a Schirmer’s tear test (STT) for the pimecrolimus and CsA groups (± standard deviation) were 3.8 ± 0.7 mm/min and 4.6 ± 0.7 mm/min, respectively. The mean increase in STT values for the pimecrolimus and CsA groups was 9.2 ± 1.6 mm/min and 5.8 ± 1.1 mm/min, respectively. Approximately 60% of the pimecrolimus-treated dogs and 50% of the CsA-treated dogs attained STT values greater than 10 mm/min. Dogs treated with pimecrolimus had significantly greater reductions in total scores for clinical signs of inflammation than did the CsA-treated group. The authors conclude that 1% pimecrolimus drops are as safe as and more effective than 0.2% CsA ointment for the control of canine KCS.

COMMENTARY: The authors of this article demonstrated that 1% pimecrolimus is effective and even superior to 0.2% cyclosporine in the treatment of KCS in the dog. Currently, compounding pharmacies formulate a 1% and 2% cyclosporine and a tacrolimus (drug related to pimecrolimus) ointment and solution. Most veterinary ophthalmologists would agree the higher concentration cyclosporine and compounded tacrolimus are also superior to the 0.2% cyclosporine tested. If pimecrolimus were manufactured as an approved veterinary product, it might then have an advantage over currently compounded drugs. Until that time, pimecrolimus has not been demonstrated to have an advantage over existing products available to the veterinarian.

Clinical evaluation of pimecrolimus eye drops for treatment of canine keratoconjunctivitis sicca: A comparison with cyclosporine A. Ofri R, Lambrou GN, Allgoewer I, et al. VET J 179:70-77, 2009.