forced diuresis

When someone has taken a poisonous dose of a drug, one strategy is to turn up the kidney's faucet so the urine flows fast and washes the drug out sooner. Forced diuresis is exactly that: deliberately increasing urine output with extra fluids, sometimes plus a diuretic, to speed a drug's exit.

Two mechanisms help. A larger, faster urine flow dilutes the drug in the tubule and reduces the contact time available for reabsorption, so more of the filtered drug stays in the urine. When combined with manipulation of urine pH, such as alkalinisation to trap a weak acid, the two effects together raise renal excretion considerably.

The technique only works for drugs that are eliminated substantially by the kidney and are not heavily protein-bound or sequestered in tissues. It also carries real dangers, since aggressive fluid loading can cause fluid overload, pulmonary oedema, and electrolyte disturbances. For these reasons modern poisoning practice uses pure forced diuresis sparingly, favouring urine alkalinisation or other antidotes where appropriate.