Short answer: Spironolactone has a half-life of about 1.4 hours (active metabolites 13.8 to 16.5 hours). Levels peak about 2.6 hours (canrenone 4.3 hours) after a dose. People vary, so treat these as estimates.
Spironolactone is an aldosterone blocker. Aldosterone is the hormone that makes the kidneys hold on to salt and water; blocking it lets more salt and water leave while potassium is kept. It is sold as Aldactone (Pfizer) and as generic tablets, for heart failure, high blood pressure, fluid build-up and too much aldosterone. It also blocks androgen receptors, which is why it causes breast growth in some men.
Also known as: Aldactone.
Aldactone comes as 25 mg, 50 mg and 100 mg tablets; the 50 mg and 100 mg tablets are scored. The label says to take it with or without food, but the same way each time, because food raises how much is absorbed.
The Aldactone label approves spironolactone for NYHA Class III to IV heart failure with reduced ejection fraction (to improve survival, manage fluid and cut heart failure hospital stays), as an add-on for high blood pressure, for fluid build-up (edema) from liver cirrhosis or nephrotic syndrome when other measures have not worked, and for primary hyperaldosteronism. Label dosing: for heart failure, 25 mg once a day, which may go to 50 mg; for high blood pressure, 25 to 100 mg a day, adjusted every 2 weeks; for edema, 100 mg a day (range 25 to 200 mg); before surgery for primary hyperaldosteronism, 100 to 400 mg a day. Use for acne or hair loss is outside the label, and the label gives no dosing for it.
The label has no boxed warning. Its main warnings are high potassium (checked within 1 week of starting or changing the dose and regularly after; higher risk with kidney problems, potassium supplements, salt substitutes, ACE inhibitors and ARBs), low blood pressure with worse kidney function from too much fluid loss, low sodium, magnesium and calcium, high blood sugar and uric acid, and breast growth in men: about 9% of men on a mean 26 mg a day developed it in the RALES heart failure trial. It is not used with high potassium, Addison's disease, or eplerenone. The full side-effect list and dosing table are on the Aldactone side effects and Aldactone dosing schedule pages.
The Aldactone label gives a mean half-life of 1.4 hours for spironolactone itself, but its active metabolites last much longer: 16.5 hours for canrenone, 13.8 hours for TMS and 15 hours for HTMS. Peak levels come 2.6 hours after a dose (4.3 hours for canrenone). Food raised absorption by about 95%. The half-life is longer in people with cirrhosis and fluid in the belly.
Numbers shown are taken from the source above. Half-life varies from person to person.
How Dose Track handles peptides · Reconstitution calculator · Half-life calculator