422 TREATMENT OF KNEE OA WITH ACETAMINOPHEN (3-4gr/day) DURING 12 MONTHS: A NATURALISTIC PROSPECTIVE STUDY

Purpose: Osteoarthritis (OA) is the more common rheumatic diseases. Acetominophen (3-4 gr/day), is a therapeutic alternative to treat symptomatic knee OA. Effectiveness and security data from long term studies using acetominophen in naturalistic conditions is scarce. To study the security and effectiveness data of acetominophen at doses of 4gr/day in real conditions during 6 and 12 months. Methods: This observational, naturalistic, open and prospective clinical trial was conducted in a Spanish rheumatology clinic. All included patients were treated with acetaminophen at doses of 4gr/day during the first 6 months, and then doses were regulated according symptoms of patients. Visits were performed at 3, 6, 9 and 12 months. Pain EVA and WOMAC were employed to quantify effectiveness. Data from security were also recorded. Results: 219 patients were included: 87.4% females, age 65.5±8.76 years and BMI 32.9±5.3. Duration of knee OA was 49.9±63.4 years. Baseline WOMAC values were: Pain = 6.9±2.8, Stiffness = 3±1.7, Function = 25±11.7. Baseline pain-EVA was 46.1±21.4. Knee OA was bilateral in 93.0% of patients. 178 patients complete the protocol at 6 months and 139 patients at 12 months. Pain-EVA [media (95% IC)] at 6 months was 37.1 (33.9-41.6) and 38.1 (33.9-42.2) at 12 months (p=0.01 and p<0.001 respectively). WOMAC values at 6 months were [media (95% IC)]: Pain = 6.6 (6.1-7.2), Stiffness = 2.7 (2.5-3.0), Function = 24.0 (22.2-25.8). WOMAC values at 12 months were: Pain = 6.4 (5.8-6.9), Stiffness = 2.8 (2.5-3.1), Function = 24.9 (23.0-26.9). At 6 and 12 months 42.9% and 40.3% of patients were responders according OARSI criteria. Two hundred forty adverse events were reported, 76% of them were low level adverse events. The most frequent adverse event was infections of respiratory tract. Eight adverse events were classified as severe, 2 of them were hepatotoxic adverse events and acetaminophen was dropped. Conclusions: In naturalistic conditions, acetaminophen at doses of 3-4gr/day reduces pain in patients with knee OA and it is a secure drug. This clinical trail was supported by Bristol-Mayers-Squibb.