Spironolactone is a long-acting aldosterone antagonist. Spironolactone is a specific pharmacologic antagonist of aldosterone, acting primarily through competitive binding of receptors at the aldosterone dependent sodium-potassium exchange site in the distal convoluted renal tubule. Spironolactone causes increased amounts of sodium and water to be excreted, while potassium and magnesium is retained.

Pharmacology

Spironolactone is a specific pharmacologic antagonist of aldosterone, acting primarily through competitive binding of receptors at the aldosterone-dependent sodium-potassium exchange site in the distal convoluted renal tubule. Spironolactone causes increased amounts of sodium and water to be excreted, while potassium is retained. Spironolactone acts both as a diuretic and as an antihypertensive drug by this mechanism. It may be given alone or with other diuretic agents which act more proximally in the renal tubule. Aldosterone interacts with a cytoplasmic mineralocorticoid receptor to enhance the expression of the Na⁺ K⁺ ATPase and the Na⁺ channel involved in a Na⁺ K⁺ transport in the distal tubule . Spironolactone bind to this mineralcorticoid receptor, blocking the actions of aldosterone on gene expression. Aldosterone is a hormone; its primary function is to retain sodium and excrete potassium in the kidneys.

Spironolactone is indicated in Congestive heart failure, Hepatic cirrhosis with ascites and oedema, Nephrotic syndrome, Primary hyperaldosteronism, Essential hypertension, For the treatment of patients with hypokalemia

Edema in adults (congestive heart failure, hepatic cirrhosis, or nephrotic syndrome): An initial daily dosage of 100 mg of Spironolactone administered in either single or divided doses is recommended, but may range from 25 to 200 mg daily. Combined therapy with other diuretics is indicated when more rapid diuresis is desired.

Primary hyperaldosteronism: After the diagnosis of hyperaldosteronism has been established, Spironolactone may be administered in doses of 100 to 400 mg daily in preparation for surgery. For patients who are considered unsuitable for surgery, Spironolactone may be employed for long-term maintenance therapy at the lowest effective dosage determined for the individual patient.

Essential hypertension: For adults, an initial daily dosage of 50 to 100 mg of Spironolactone administered in either single or divided doses is recommended.

Hypokalemia: Spironolactone in a dosage ranging from 25 mg to 100 mg daily is useful in treating a diuretic-induced hypokalemia.

Spironolactone is contraindicated in patients with acute renal insufficiency, significant impairment of renal function, anuria, hyperkalaemia or sensitivity to Spironolactone.

Gynaecomastia may develop in association with the use of Spironolactone. Other adverse reactions are: GI symptoms including cramping and diarrhoea, drowsiness, lethargy, headache, urticaria, mental confusion, impotence, irregular menses or amenorrhoea and post-menopausal bleeding.

Overdose Effects

Symptoms of overdosage include drowsiness, mental confusion, dizziness, diarrhea and vomiting etc. Patients should induce vomiting or evacuate the stomach by lavage during Spironolactone overdoasge.

All patients receiving diuretic therapy should be observed for evidence of fluid or electrolyte imbalance. Hyperkalemia may occur in patients with impaired renal function or excessive potassium intake and can cause cardiac irregularities, which may be fatal.

Pregnancy & Lactation

Pregnancy: Spironolactone should not be used during pregnancy

Lactation: Canrenone, an active metabolite of Spironolactone, appears in breast milk. If use of the drug is deemed essential an alternative method of infant feeding should be instituted.