hydrochlorothiazide

Hydrochlorothiazide is a thiazide diuretic used to treat hypertension and edema. It lowers blood pressure and reduces fluid buildup by increasing the excretion of sodium and chloride in the distal convoluted tubule of the kidney, which reduces plasma volume over time.

Mechanism of action involves inhibition of the Na-Cl cotransporter in the distal tubule. This decreases reabsorption of sodium and chloride, promoting water loss. The increased delivery of sodium to the distal nephron can also promote potassium loss, leading to a risk of hypokalemia. Thiazides can cause mild metabolic alkalosis as a secondary effect of diuresis.

Indications include essential hypertension, edema associated with heart failure, liver cirrhosis, or nephrotic syndrome, and prevention of calcium-containing kidney stones. It is sometimes used as part of combination therapy for resistant hypertension.

Pharmacokinetics: hydrochlorothiazide is taken by mouth, with onset of action typically within 1–2 hours and a duration of effect that may extend through the day. It is absorbed variably and excreted primarily by the kidneys in an unchanged form. It is available in oral tablet form and can be used alone or with other antihypertensive agents.

Adverse effects include electrolyte disturbances such as hypokalemia and hyponatremia, hyperuricemia which can precipitate gout, and potential dehydration. Hyperglycemia risk may be increased in susceptible individuals, and photosensitivity can occur.

Interactions and contraindications: NSAIDs can reduce diuretic efficacy; caution with other blood pressure–lowering drugs. Not recommended in anuria or severe renal impairment; use with caution in gout, diabetes, or pregnancy. Hypersensitivity to sulfonamides is a consideration for some patients.