Lithium carbonate--a competitive aldosterone antagonist?

Plasma renin activity (PRA), aldosterone (aldo) levels, electrolyte levels, and blood pressures were measured in 16 patients with affective disorders taking lithium prophylactically, and in 16 age and sex-matched control subjects. PRA and aldo levels were significantly elevated in the lithium-treated group. There was no difference between the groups in plasma electrolytes or erect and supine blood pressures, arguing against secondary aldosteronism. In the lithium-treated group, there was a significant positive correlation between both PRA and plasma aldo vs serum lithium. We postulate that lithium inhibits the action of aldosterone on the distal tubule in the kidney. Activation of the renin angiotensin system maintains normal blood pressure and plasma electrolytes.