• Oral

      • Fairly rapidly absorbed from the gastrointestinal tract

      • Food increases the bioavailability of unmetabolized spironolactone by almost 100%.



    • Spironolactone and its metabolites are more than 90% bound to plasma proteins.


    • Spironolactone is a synthetic 17-lactone steroid

    • Renal competitive aldosterone antagonist

    • On its own, spironolactone is only a weak diuretic

      • It may be given alone or with other diuretic agents which act more proximally in the renal tubule

    • Due to its anti-androgen effect, it can also be used to treat hirsutism

      • Common component in hormone therapy for male-to-female transgendered people

    • Spironolactone inhibits the effect of aldosterone by competing for intracellular aldosterone receptor in the distal tubule cells

      • Antagonises a cytoplasmic mineralocorticoid receptor responsible for enhancing expression of Na+, K+-ATPase and the Na+ channel involved in a Na+ K+ transport in the distal tubule

      • This increases the secretion of water and sodium, while decreasing the excretion of potassium

    • Spironolactone has a fairly slow onset of action, taking several days to develop and similarly the effect diminishes slowly.


    • Half-life 10 mins

    • Rapidly and extensively metabolized

      • Divided into two main routes

        • those in which the sulfur moiety is retained

        • those in which the sulfur moiety is removed by dethioacetylation.

      • Transformed to a reactive metabolite

        • Can inactivate adrenal and testicular cytochrome P450 enzymes

        • Has anti-androgenic activity.

    • Excreted primarily in the urine and secondarily in bile

Side effects

    • Oral LD50 of spironolactone is greater than 1,000 mg/kg in mice, rats, and rabbits

    • Acute overdosage of spironolactone may be manifested by:

      • Drowsiness, mental confusion, maculopapular or erythematous rash, nausea, vomiting, dizziness, or diarrhea

    • Spironolactone has been shown to be a tumorigen in chronic toxicity studies in rats.