diuretic
n. a substance that increases the flow of urine. Diuretics may be endogenous agents (e.g., dopamine) or prescription or nonprescription drugs (e.g., thiazide diuretics). Many diuretics (including thiazides) work by inhibiting or blocking the reabsorption of sodium and potassium ions from the kidney filtrate, so that less water is reabsorbed across the kidney tubules. Others, called osmotic diuretics, increase the osmolality of the filtrate. Both mechanisms result in increased urine volume. Some diuretics may produce adverse effects with psychological implications, for example, lassitude, weakness, vertigo, sexual impotence, headaches, polydipsia (intense thirst), irritability, or excitability.