Chlortalidone

Chlortalidone, also known as chlorthalidone in some regions, is a thiazide-like diuretic used in the management of hypertension and edema due to heart failure, liver disease, or nephrotic syndrome. It is characterized by a long duration of action, often providing antihypertensive effects for 24 to 72 hours, which supports once-daily dosing. The drug is available in oral tablet form, and may be prescribed as a sole agent or in combination with other antihypertensive medications.

Mechanism of action involves inhibition of the sodium-chloride cotransporter in the distal convoluted tubule of the nephron. This reduces sodium and water reabsorption, increasing their excretion. Potassium and magnesium excretion may increase, while calcium reabsorption is enhanced. The overall effect is a reduction in plasma volume and blood pressure, with additional effects on mineral balance.

Indications and dosing vary by condition. For hypertension, typical starting doses are around 12.5 mg once daily, with potential titration to 25 mg daily; higher doses may be used in some regimens. For edema, dosing can range higher, often up to 100 mg daily in divided or single daily doses, depending on response and tolerance. Dosing should be guided by clinical response and electrolyte monitoring, as diuretic effects can take several days to manifest.

Safety, adverse effects, and interactions are important considerations. Common adverse effects include increased urination, dizziness, and electrolyte disturbances such as hypokalemia and hyponatremia. Hyperuricemia can raise the risk of gout, and there may be effects on glucose tolerance, which is a consideration for patients with diabetes. Photosensitivity, dehydration, and comparisons with sulfonamide hypersensitivity are also noted concerns. Caution is advised in pregnancy, kidney impairment, and in patients taking NSAIDs, lithium, or other drugs that affect electrolyte balance.