Evaluation of tramadol for treatment of osteoarthritis in geriatric cats.

OBJECTIVE To evaluate tramadol for treatment of signs of pain and impaired mobility in geriatric cats with osteoarthritis. DESIGN Randomized controlled crossover trial. ANIMALS 24 client-owned geriatric (≥ 10 years old) cats with osteoarthritis. PROCEDURES Otherwise healthy cats with owner-identified mobility impairment and clinical and radiographic evidence of osteoarthritis involving at least 1 appendicular joint were enrolled in the study. Cats were treated with tramadol orally at dosages of 0 (placebo), 1, 2, and 4 mg/kg (0, 0.45, 0.9, and 1.8 mg/lb) twice a day for 5 days, with a 2-day (weekend) washout period between treatments. Mobility was assessed with a collar-mounted activity monitor system, and impairments in activity were assessed with a client-completed questionnaire. RESULTS 17 cats completed the study; 7 cats were withdrawn. There was a significant increase in activity with the 2-mg/kg dosage of tramadol, compared with activity when cats received the placebo. Significantly more owners (11/18) considered their cats to have improved with the 2-mg/kg treatment, compared with all other dosages (6/19 to 8/21). Most owners (17/20 [85%]) considered their cat's global quality of life to have improved during the study. Adverse events, predominantly euphoria, dysphoria, sedation, decreased appetite, and diarrhea, were significantly more frequent with the 4-mg/kg (8/19) and 2-mg/kg (6/18) treatments but not with the 1-mg/kg (2/21) treatment, compared with frequency of adverse events with the placebo (0/21). CONCLUSIONS AND CLINICAL RELEVANCE Results suggested a beneficial effect of twice-daily oral administration of tramadol at a dosage of 2 mg/kg in geriatric cats with osteoarthritis. Adverse events were dose dependent, and caution should be exercised in cats that have concurrent disease or are receiving other drugs that may produce adverse gastrointestinal effects.