Multicenter, randomized, double-blind, active-controlled, parallel-group trial of the long-term (6-12 months) safety of acetaminophen in adult patients with osteoarthritis.

Objective: This study evaluated the safety of acetaminophen 4 g/d administered for up to 12 months to adult patients with osteoarthritis pain, using naproxen 750 mg/d as an active comparator.

Methods: This multicenter, multidose, single-dummy, randomized, double-blind, active-controlled, parallel-group study enrolled patients with mild to moderate osteoarthritis pain of the hip or knee. Patients received acetaminophen 4 g/d or naproxen 750 mg/d for 12 months (group 1) or 6 months (group 2).