To examine the efficacy and safety of two doses of long-acting acetaminophen in patients with osteoarthritis (OA) of the hip or knee.
This multicenter, randomized, double-blind, parallel-group, placebo-controlled study evaluated the efficacy and safety of acetaminophen extended-release (ER) 650 mg and 1300 mg given three times daily for the treatment of moderate to moderately severe OA of the hip or knee. Primary efficacy end points were mean change from baseline through 12 weeks in the Western Ontario and McMaster Universities Osteoarthritis Index pain and physical function subscale scores and mean patient global assessment of response to therapy at week 12. Safety assessments included monitoring vital signs, adverse events, study joint assessments, and clinical laboratory results at each study visit.
Four hundred eighty-three patients were randomized to treatment and included in the intent-to-treat analysis. All groups were similar with respect to baseline demographics except for gender, weight, and body mass index. Acetaminophen ER 3900 mg was significantly superior to placebo for all three primary end points; acetaminophen ER 1950 mg was significantly superior to placebo only with respect to patient assessment of response to therapy. Study treatments were generally well tolerated, and there was no significant difference among the groups in the overall number of adverse events.
Acetaminophen ER 3900 mg/d administered for up to 12 weeks was effective in treating moderate to moderately severe chronic OA pain of the hip or knee and was generally well tolerated.