of osteoarthritis. The aim of the study was the evaluation of efficacy of chronic pain treatment with modified

extended‑release ketoprofen in monotherapy or polytherapy in osteoarthritis and the monitoring of possible

adverse events. Material and methods: Twenty‑three thousand two hundred and forty patients treated with

extended‑release ketoprofen for 3±2 weeks because of pain associated with osteoarthritis participated in post‑marketing survey. Pain intensity was assessed in a 10‑point visual analogue scale (VAS). Results:

The intensity of pain in patients treated with extended‑release ketoprofen preparations at a dose of 154±41 mg and other analgesics (32.7% of respondents) was 5.28±1.97 points. During a subsequent visit, previous treatment was maintained in 66.8% patients, including 51.8% patients on ketoprofen monotherapy and 15.0% treated with additional anti‑inflammatory agent. Daily dose of ketoprofen was increased in 27.9% patients, while in 7.7% of patients an increase or the use of another anti‑inflammatory drug was recommended. Twelve point four percent of patients reported at control visit discontinued the treatment with ketoprofen. A more marked reduction of pain intensity was observed in patients with increased (by an average of 60 mg) extended‑release ketoprofen dose (‑60.7%), than in those with increased dose or use of another anti‑inflammatory drug (‑44.0%). Adverse events was reported by 11.67% responders. Ketoprofen therapy was discontinued by 29.5% of patients who experienced an adverse drug reaction and by 10.2% of patients without any side effect. Non‑occurrence of adverse drug reaction was associated with a 3.69‑fold greater chance of treatment continuation. Conclusions: 1) Extended‑release ketoprofen preparations in monotherapy allow a satisfactory pain control in half of patients with osteoarthritis. 2) Adverse drug reactions associated with the use of ketoprofen preparations cause discontinuation of treatment in every third patient.