Osteoarthritis pain is a significant problem for our aging population. Non-steroidal anti-inflammatory drugs and opioids are effective treatments, but have significant adverse effects, so there is a need for alternative treatments. Selective norepinephrine-serotonin reuptake inhibitor antidepressants may provide a new treatment option for osteoarthritis pain.
We performed a single-blind placebo run-in trial of 150-225 mg of venlafaxine in 18 subjects with activity-limiting osteoarthritis pain. Each subject received 2 weeks of placebo followed by 10 weeks of venlafaxine. The primary outcome was reduction in average pain intensity between 2 and 12 weeks. For subjects not completing the trial, their last observation was carried forward as an imputed outcome.
Average pain on the Brief Pain Inventory (BPI) was 4.7 at baseline, 4.4 after the 2-week placebo run-in, and 3.3 at 12 weeks (25% decrease, P = 0.03). Nine subjects (50%) reported at least 30% pain reduction between weeks 2 and 12. The Western Ontario and McMasters University Osteoarthritis Index (WOMAC) pain score at baseline was 2.0, 1.8 after 2 weeks, and 1.7 after 12 weeks. This represented a 6% decrease in pain between weeks 2 and 12 (P = 0.42), with two subjects (11%) reported at least 30% pain relief between weeks 2 and 12 on the WOMAC. Effects on self-reported physical and role function and depression were marginal or non-significant, and observed physical function did not improve.
Venlafaxine significantly reduced pain intensity on the BPI and marginally improved self-reported function. Venlafaxine should be investigated further in a larger randomized trial for the treatment of osteoarthritis pain.