Closely monitor patients w/ chronic lung function impairment, especially asthma, for risk of hypersensitivity. Potential risk of cross sensitivity reactions w/ sulphasalazine. Possible severe photosensitivity reactions in patients w/ pre-existing skin conditions (eg, atopic dermatitis & eczema). Perform haematological investigations if patient develops unexplained bleeding, bruising, purpura, anaemia, fever or sore throat. Terminate treatment if there is blood dyscrasia suspicion. Patients w/ conditions predisposing to myo- or pericarditis development. W/draw promptly if acute intolerance syndrome is suspected. Increased liver enzyme levels. May delay onset of action by organic or functional obstruction in the upper GIT. May lead to falsely elevated test results when measuring urinary normetanephrine by liqd chromatography w/ electrochemical detection. Nephrolithiasis; ensure adequate fluid intake during treatment. Patients w/ confirmed mild to moderate renal impairment. Evaluate renal function prior to initiation of therapy & at least twice a yr, while on treatment. Hepatic impairment. Pregnancy & lactation. Not recommended in childn <18 yr.