Switching from NSAIDs to paracetamol: a series of n of 1 trials for individual patients with osteoarthritis.

OBJECTIVES To investigate for individual patients who have been using NSAIDs regularly, whether paracetamol is as effective as non-steroidal anti-inflammatory drugs (NSAIDs) in the treatment of pain and disability related to osteoarthritis of the hip or knee. METHODS A series of n of 1 trials were conducted in general practices in Amsterdam and the surrounding area. Each patient was his or her own control and received five pairs of treatments comprising two weeks of an NSAID and two weeks of paracetamol. For each pair, the order of treatments was randomised. Outcome measures were severity of individual main complaints, intensity of pain, satisfaction with drugs, function test, and side effects. RESULTS Thirteen patients were selected. Six patients did not complete the study. For five patients completing the study little or no difference was found between NSAIDs and paracetamol, for one patient the results favoured the NSAID, and for one patient there was no association between outcome and type of drug. It was recommended that six patients changed to paracetamol; the others continued with NSAIDs. Three months after the end of the study, four of the six patients for whom paracetamol had been recommended were taking NSAIDs for practical reasons or perceived lack of efficacy. CONCLUSION The results of the n of 1 trials varied across patients. n of 1 trials can be used to investigate which treatment is best for any specific person, thus avoiding unnecessary prolonged treatment with NSAIDs. However, practical reasons may cause patients to switch from NSAIDs to paracetamol or not.