Diuretics 'water tablets', are a class of drug which cause the kidney to produce more urine. Examples of this type of drug include: Bendroflumethiazide, Furosemide, Bumetanide, Metolazone, Spironolactone.

Mechanism of action

Different diuretics act on different parts of the nephron, a tiny structure of which there are approximately 1 million in the kidney! All diuretics ultimately promote the production of urine. This is particularly useful in conditions where an excess of body fluid occurs, for example cardiac failure and liver failure. The resultant reduction of fluid in the blood stream also lowers the blood pressure so these drugs can also be used for hypertension. Caffeine and alcohol both act as diuretics.

Potential side-effects

Common side effects include mild gastrointestinal symptoms, a drop in blood pressure and altered levels of potassium and sodium in the body. Occasionally kidney failure can occur. This is more common in the elderly and in the context of another illness (for example diarrhoea and vomiting - both causing additional fluid losses). Should any of these  side effects occur your diuretic dose may need to be adjusted or stopped entirely.