Guedes AGP, Meadows JM, Pypendop BH, Johnson EG. Evaluation of tramadol for treatment of osteoarthritis in geriatric cats. J Am Vet Med Assoc. 2018 Mar 1;252(5):565-571. PubMed PMID: 29461159.
Tramadol is a commonly used pain control medication in human and veterinary medicine. It has multiple modes of action, but the primary effect is due to its metabolism into an opioid. However, there has been significant doubt as to its efficacy in dogs due to the lack of production of the active metabolite. Recent data has suggested that in a clinical setting, tramadol is not effective in canine species. In cats (as in humans) the active metabolite of tramadol is produced, suggesting it is likely more effective in this species, and laboratory analysis has suggested good efficacy for pain control.
The purpose of this study was to determine the efficacy of tramadol for pain control in geriatric cats with osteoarthritis. The study was designed as a prospective double blind placebo controlled crossover trial.
Cats over 10 years of age presenting to a university veterinary hospital with owner reported mobility impairment were recruited. They received physical, neurologic, and orthopedic exams, CBC/biochemistry, and radiographs of joints with pain or reduced range of motion. Cats were included if they had radiographic evidence of osteoarthritis in at least one joint, were indoor only, and had owner reported reduced mobility. They were excluded for any biochemical or physical exam evidence of systemic disease, use of NSAIDs or other pain medications, or use of disease-modifying osteoarthritis agents (ie glucosamine). 24 cats were included in the study.
Cats received capsules containing either sucrose or tramadol at 1, 2, or 4 mg/kg every 12 hours for Monday to Friday, and received no drugs on weekends. After each weekend, the cat was randomly rotated to another treatment group until all cats had received all therapies. Cats wore a collar mounted activity monitor to track activity level. Owners evaluated three pre-determined time and place impaired activities using a CSOM questionnaire.
Daily activity level was found to be statistically significantly higher for the 2mg/kg dose than placebo. No other doses were significantly different. CSOM scores showed that cats on the 2mg/kg dose were significantly improved compared to other treatments. CSOM did not significantly differ between other treatments and did not show improvement relative to when the cat was normal. 85% of owners reported that global quality of life improved over the course of the study.
Adverse effects occurred primarily in the 4mg/kg group and were generally either opioid related (mydriasis, euphoria, restlessness, etc) or gastrointestinal in origin.
Cats at the 2mg/kg dose had an improved activity level and CSOM score compared to cats at all other doses, suggesting clinical efficacy of the drug for pain control in osteoarthritis in a real-world setting.
Some drawbacks to this study are present. There is some evidence that activity monitors in cats may not be accurate assessments of centrally acting drugs due to changes in activity level. The reason for lack of efficacy in the 4mg/kg group may be due to excessive sedation from the higher dose leading to decreased activity levels. Larger sample sizes and longer periods of therapy may also have improved significance and given more information.
Based on the findings of this study, tramadol at a dose of 2mg/kg is likely effective in the treatment of arthritis pain in geriatric cats. (MRK)
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