Creatine tolerance test

Statins are well absorbed after administration orally, and are metabolised in the liver. They are well tolerated, the commonest adverse effect being transient, and usually minor abnormality of liver function tests in some 1% of patients. Asymptomatic elevation of muscle enzymes (creatine phos-phokinase, CPK) and myositis (with a generalised muscle discomfort) occur more rarely, but is more frequent when statins are combined with other anti-hyperlidaemic drugs such as fibrates and nicotinic acid patients should be counseled about myositis when these drugs are co-administered. Myositis is also more likely with co-administered anti-HIV protease inhibitors, and with drugs that interfere with metabolism of some statins, e.g. ciclosporin. 

A test for the investigation of myopathies in which creatine is given orally and its output in the urine is measured. Increased urine creatine excretion (i.e. reduced tolerance) is found when the muscle mass is reduced or the muscle is unable to take up creatine (e.g. hyperthyroidism and muscular dystrophy). Decreased urinary creatine excretion (i.e. increased tolerance) is. found in hypothyroidism. 

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