A means of encouraging excretion via the kidneys of a compound by altering the pH (acidity) and increasing the volume of the urine. Forced diuresis is occasionally used after drug overdoses, but is potentially dangerous and so only suitable where proper intensive monitoring of the patient is possible. Excretion of acid compounds, such as salicylates, can be encouraged by raising the pH of the urine to 7-5—8-5 by the administration of an alkali such as bicarbonate (forced alkali diuresis). The excretion of bases, such as amphetamines, can similarly be encouraged by lowering the pH of the urine to 5.5—-6-5 by giving an acid such as ammonium chloride (forced acid diuresis).