hydrochlorotiazyd

Hydrochlorothiazide, commonly known as HCTZ, is a thiazide-type diuretic used to treat essential hypertension and edema from conditions such as congestive heart failure, cirrhosis, and nephrotic syndrome. It is also used to prevent calcium-containing kidney stones in people with hypercalciuria. The drug is available in oral form as a generic medication and under various brand names.

Mechanism of action and pharmacology: Hydrochlorothiazide acts on the distal convoluted tubule of the kidney, inhibiting the Na+-Cl− cotransporter. This reduces the reabsorption of sodium and chloride, increasing their excretion along with water. The initial blood pressure decrease is due to volume reduction, while long-term effects involve a reduction in peripheral vascular resistance. After oral administration, peak concentrations typically occur within a few hours, and the drug is primarily excreted by the kidneys.

Indications and dosing: Common indications include essential hypertension and edema associated with heart failure, liver cirrhosis, or nephrotic syndrome. It may be used alone or in combination with other antihypertensive agents. Typical starting doses range from 12.5 to 25 mg once daily, with potential adjustments up to 50 mg daily based on response and tolerance. Caution is advised in patients with renal impairment or gout, and care is taken in those with electrolyte disturbances.

Side effects and safety: The most frequent adverse effects are electrolyte imbalances such as hypokalemia and hyponatremia, as well as dehydration. Hyperuricemia can precipitate gout, and glucose tolerance may be affected, which is of concern for patients with diabetes. Other potential effects include photosensitivity and, rarely, hypersensitivity reactions. Interactions can occur with NSAIDs, lithium, and other antihypertensives, potentially altering diuretic efficacy or safety.

History and classification: Hydrochlorothiazide belongs to the benzothiadiazide class of thiazide diuretics, with a long history of widespread clinical use since the late 1950s. It remains a first-line option in many guidelines for the management of hypertension and related edemas.