A number of drugs can affect potassium levels by a variety of different mechanisms. Diuretics remain the most important cause of drug-induced alterations. ACE inhibitors may produce hyperkalaemia, particularly in patients with autonomic neuropathy, adrenal insufficiency, renal impairment and when used in combination with nonsteroidal anti-inflammatory drugs (NSAIDs). Cathartic and/or diuretic abuse should be suspected when hypokalaemia occurs in young patients suspected of having an eating disorder. NSAIDs may occasionally produce hyperkalaemia, particularly in patients with renal impairment or when used with ACE inhibitors. Sympathomimetics and theophylline derivatives may lower serum potassium levels, but this is usually only of clinical significance when overdosage occurs.