Mild to moderate impaired renal or hepatic function (test serum creatinine before treatment, every 3 mth for 1st yr, every 6 mth for next 4 yr, then annually). Elderly; active peptic ulcer; pregnancy, lactation; patients predisposed to pericarditis or myocariditis. Counsel patients to report any unexplained bleeding, bruising, purpura, sore throat, fever or malaise during treatment; perform blood count and stop treatment if blood dyscrasias suspected. Counsel patients taking delayed release tablets to report repeatedly unbroken or partially broken tablets in their faeces. Pyloric stenosis may delay release into colon.