Spironolactone is the generic name of a synthetic steroid (the brand name is Aldactone). It inhibits the action of aldosterone, reducing salt and fluid retention by the kidneys, but unlike other similar medications, it does not hurt the retention of potassium. It is a diuretic. It works best with a sufficient sodium supply in the body, and people taking it often crave salt more than people not using the drug.

Spironolactone is also useful for lowering blood pressure, usually with another drug, in cases where the patient suffers from low potassium. It is also an anti-androgen, making it rarely prescribed for male patients. It is very commonly prescribed for transsexual hormone therapy for male-to-female patients due to the anti-androgen effects.

The drug is metabolized rapidly and extensively. Taking it after meals increased the bioavailability of unmetabolized spironolactone by almost 100%.

It is available in 25mg, 50mg, and 100mg tablets. Dosage is usually between 25mg to 200mg, depending on the condition it's being taken for, and the amount of time the patient is taking the medication.

Drug Interactions:

Because the drug can raise blood potassium in the body, it should not be administered with other drugs that can increase potassium, as excessively high levels can lead to abnormalities in the heart rhythm. It can also cause elevation of blood digoxin (Lanoxin) levels, which can require adjustment in the dosage. There may be increased responsiveness to muscle relaxants. It should not be taken with Lithium, as the diuretic effects cause higher retention, and increase the risks of lithium toxicity.

Side Effects:

Because of the anti-androgen properties, gynecomastia (enlargement of the breasts) is not infrequent, especially among men who take this drug. (10% of men treated with this drug have experienced it, and over half with a dosage of 150 mg/day) Rare side effects include diarrhea, cramps, drowsiness, rash, impotence, irregular menstrual peroids, and irregular hair growth. Gastric bleeding, ulceration, nausea, and vomiting also sometimes occur, and a very few cases of mixed cholestatic/hepatocellular toxicity have occured, with one reported fatality.

It has also been found to be a tumorigen in chronic toxicity studies in rats. Unnecessary use of this drug should be avoided. (Personal note: I really, really, REALLY don't like seeing this, not one bit. Especially since I've been taking this for over 3 years, and will continue to do so for at least a few more.)

Canrenone, one of the major metabolites of spironolactone, and an active one, appears in human breast milk. It is recommended that a woman on spironolactone not breast feed, or find an alternative medication.

Sources:
RxList - http://www.rxlist.com
Informed Online - http://www.infomed.org/100drugs/spitoc.html
Focus on Medications - http://www.focusonmedications.com/Script/Main/Art.asp?li=MNI&ArticleKey=687

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