Should duloxetine be added to exercise to treat sedentary patients with painful knee osteoarthritis? : A pilot study

Abstract

Introduction: In knee osteoarthritis patients that benefit from chronic pain management and physical activity, the additional impact of duloxetine over and above exercise is yet to be determined. Our goal was to study the effects of duloxetine on muscle mass, strength, physical performance, pain, stiffness and physical function in sedentary patients with painful knee osteoarthritis treated with a home-based exercise (HE) program. Methods: Adults with painful knee osteoarthritis and lower physical performance were assigned to receive duloxetine (60mg/d) or placebo, in addition to HE therapy. The primary endpoint was the difference in short physical performance battery (SPPB) between groups at week 12. Secondary endpoints included 12-week changes in muscle mass by dual-energy X-ray absorptiometry (appendicular skeletal muscle mass index – ASMI), strength by handgrip (HG) and knee extension (KE) maximal isometric voluntary contraction, pain by visual analog scale (VAS) and pain, stiffness and physical function by Western Ontario McMaster Universities (WOMAC) questionnaire. Results: Twenty-four participants were included. After 12 weeks, HE+duloxetine showed no benefit in SPPB when compared to HE+placebo (p=0.456) and both groups significantly improved SPPB when compared to baseline [HE+duloxetine: 1.52 (95%CI 0.53 to 2.51); HE+placebo: 2.00 (95%CI 1.23 to 2.77)]. Both groups significantly improved WOMAC, with no differences between them (p=0.389). Only HE+duloxetine group improved pain VAS [-2.26cm (95%CI -4.08 to -0.44)], while only HE+placebo group improved ASMI [0.4Kg/m2 (95%CI 0.0 to 0.9)] and KE strength [11.8Kg (95%CI 4.3 to 19.2)]. HE+duloxetine group performed less minutes of exercise than HE+placebo group (310 vs. 692, p=0.015). Adverse events rates were similar between groups. Conclusions: Duloxetine did not additionally improve physical performance, pain, stiffness and physical function of patients with lower physical performance and painful KOA treated with exercise. Muscle mass and muscle strength gains were only observed in the placebo group perhaps due to greater exercise adherence, but larger studies are needed to address this hypothesis.