Retrospective cohort study on the development of keratoconjunctivitis sicca in dogs treated with trimethoprim sulfonamide: a VetCompass Australia study

BACKGROUND: Keratoconjunctivitis sicca (KCS) is a common and important eye disease of dogs and has been associated with the administration of trimethoprim sulfonamide (TMS). HYPOTHESIS/OBJECTIVES: Determine the prevalence of KCS after TMS treatment at a population level and describe risk factors for KCS development. ANIMALS: Dogs evaluated in general veterinary practice in Australia with records in VetCompass Australia between 2012 and 2022. METHODS: Natural language processing was used to detect dogs treated with TMS and to detect dogs that subsequently developed KCS. Cox proportional hazards modeling was performed to investigate risk factors such as drug dose, duration of treatment, and patient level characteristics (breed, age, sex). RESULTS: A total of 2243 dogs were treated with TMS during the study period. Four definitive cases of KCS and an additional 35 cases of possible KCS were detected (prevalence 1.8%; 95% confidence interval [CI], 1.3-2.5%). Median duration of TMS treatment was 10 days for both cases (interquartile range [IQR], 7-17 days) and non-cases (IQR, 7-15 days). Median doses were 32 and 33 mg/kg/day for cases and non-cases, respectively. Trimethoprim sulfonamide dose and duration of treatment were not associated with KCS. Some breeds were over-represented and older dogs were more likely to be affected (hazard ratio [HR], 1.076; 95% CI, 1.005-1.152; P = .04). CONCLUSIONS AND CLINICAL IMPORTANCE: Keratoconjunctivitis sicca is rare in dogs treated with TMS.