Article: Spironolactone

Spironolactone
Systematic (IUPAC) name
?
Identifiers
CAS number	52-01-7
ATC code	C03DA01
PubChem	5833
DrugBank	APRD01234
Chemical data
Formula	C24H32O4S
Mol. weight	416.574 g/mol
Pharmacokinetic data
Bioavailability	?
Metabolism	?
Half life	10 minutes
Excretion	?
Therapeutic considerations
Pregnancy cat.	C (USA); B3 (Aus)
Legal status
Routes	?

Spironolactone (marketed as Aldactone®, Novo-Spiroton®, Spiractin®, Spirotone®, or Berlactone®) is a synthetic 17-lactone steroid which is a renal competitive aldosterone antagonist in a class of pharmaceuticals called potassium-sparing diuretics, used primarily to treat low-renin hypertension, hypokalemia, and Conn's syndrome. On its own, spironolactone is only a weak diuretic, but it can be combined with other diuretics. Due to its anti-androgen effect, it can also be used to treat hirsutism, and is a common component in hormone therapy for male-to-female transgendered people. Also used for treating hair loss.

Mechanism of action

Spironolactone inhibits the effect of aldosterone by competing for intracellular aldosterone receptor in the distal tubule cells. 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. Spironolactone has anti-androgen activity by binding to the androgen receptor and thus preventing it to interact with dihydrotestosterone.^[1]

Pharmacokinetics

Spironolactone is fairly rapidly absorbed from the gastrointestinal tract. It is also rapidly metabolised and bound in plasma proteins. Many of its metabolites are also active and one of them, canrenone as potassium canrenoate, is used parenterally when rapid effect is needed. Spironolactone's half-life is only 10 minutes, but canrenone's half-life is 10 to 35 hours, depending on the dose. The main elimination route is in the urine and some also in the bile.

Adverse effects and interactions

Spironolactone can cause gastrointestinal problems fairly often. Since it also affects steroid receptors elsewhere in the body, it can cause gynecomastia, menstrual irregularities and testicular atrophy. Other side effects include ataxia, impotence, drowsiness and rashes. A carcinogenic effect has been demonstrated in rats. [2]

People using this drug should avoid salt substitutes.^[2]

See also

• Baldness treatments