Intraindividual differences in pain relief and functional improvement in osteoarthritis with diclofenac or tramadol

Objectives: To investigate how individual patients with painful osteoarthri tis (OA) respond to the non-steroidal anti-inflammatory drug (NSAID) diclof enac and the centrally acting analgesic tramadol when individual on-demand dose titration is allowed. In addition, we studied whether the differences in the mode of action of the different analgesics were important for functi onal outcome in OA patients. Methods: This was performed as a double-blind, crossover: randomised study in 60 patients with OA of the hip (19 patients) or knee (41 patients) witho ut clinical joint inflammation. Patients received either tramadol (50 to 10 0mg up to three times daily, on demand) for 4 weeks, followed by diclofenac (25 to 50mg up to three times daily, on demand) for 4 weeks, or vice versa . The multidimensional 'Western Ontario and McMaster Universities Osteoarth ritis Index' (WOMAC) questionnaire (pain, stiffness and functional impairme nt) was used to assess the effect of the drugs on pain and functional capab ility. Results: 54 patients completed both study periods. The mean (+/- SD) daily dose of tramadol consumed was 164.8mg (+/- 54.1 mg) and that of diclofenac was 86.9mg (+/- 21.4mg). Both treatments modestly improved median pain inte nsity, paralleled by an improvement in functional parameters, and there wer e no statistically significant differences between the groups. However, ind ividual treatment effects varied greatly, and within individual patients th ere were considerable variations in analgesic effectiveness between the two treatments. Consistently, pain relief correlated linearly with functional improvement. More patients reported adverse events with tramadol than with diclofenac (20 vs 3%, p = 0.0056), but there was no difference in adverse e vent-related withdrawals (p = 0.69). Conclusion: OA patients' response to analgesic treatment was highly individ ual and the response to one drug was not predictive of that to another drug . A significant proportion of patients were not treated satisfactorily with diclofenac or tramadol alone. The results obtained from a descriptive anal ysis of group effects (means, medians) were inappropriate for drawing concl usions on individual treatment benefits. Improvement of functional capabili ty apparently was a consequence of pain relief. Effective pain relief shoul d therefore be the main therapeutic goal in patients with OA where inflamma tion is less prominent.