Comparative efficacy and tolerability of two sustained-release formulations of diclofenac: results of a double-blind, randomised study in patients with osteoarthritis and a reappraisal of diclofenac's use in this patient population.

Objective: To compare the analgesic efficacy and tolerability of a sustained-release pellet formulation of diclofenac (Olfen-100 SR Depocaps, SR-CAP, Mepha Ltd, Aesch, Switzerland) with the standard reference formulation (Voltaren retard 100, SR-TAB, Novartis Pharma AG, Basel, Switzerland), both containing 100 mg diclofenac sodium, in patients with osteoarthritis (OA) of the knee and/or hip. In addition, diclofenac's current place in the symptomatic therapy of OA is briefly reviewed.

Methods: In this 2-week double-blind, active-controlled, non-inferiority trial, 210 OA patients were randomised to receive either SR-CAP once daily or SR-TAB once daily (n = 105 for both groups). The primary efficacy endpoint was the change in visual analogue scale (VAS) pain score (0-100 mm) at rest at Day 14 compared with baseline. Secondary variables included the change in VAS pain score on movement and global assessments of efficacy and tolerability using verbal rating scales (VRS).

Results: Between baseline and Day 14, mean +/- SD VAS pain score at rest decreased by 44.4 +/- 18.5 mm in the SR-CAP group (n = 89) compared with 41.2 +/- 19.8 mm in the SR-TAB group (n = 82) based on the per protocol population. Comparable changes were observed in the intention-to-treat population. The lower bound of the 1-sided 97.5% confidence interval was -2.7 mm and greater than the prespecified non-inferiority limit of -10 mm. There was a trend towards a better tolerability with SR-CAP compared with SR-TAB based on mean +/- SD VRS scores (SR-CAP, 0.6 +/- 0.68; SR-TAB, 0.9 +/- 1.0 for assessment by patients; p = 0.063).

Conclusion: SR-CAP is as effective as and possibly better tolerated than SR-TAB in patients suffering from painful OA.