Overview
Irbesartan/Hydrochlorothiazide is a fixed-dose combination antihypertensive medication containing an angiotensin II receptor blocker (ARB) and a thiazide diuretic. It is used for the treatment of hypertension when monotherapy provides inadequate blood pressure control.
Mechanism of Action
Irbesartan selectively blocks the binding of angiotensin II to the AT1 receptor, inhibiting vasoconstriction and aldosterone secretion. Hydrochlorothiazide inhibits sodium reabsorption in the distal convoluted tubule, promoting sodium and water excretion, reducing plasma volume.
Indications
- Hypertension
Dosage
Available as irbesartan 150 mg/hydrochlorothiazide 12.5 mg and irbesartan 300 mg/hydrochlorothiazide 12.5 mg tablets. Usual starting dose is one tablet daily, titrated based on blood pressure response. Maximum dose: irbesartan 300 mg/hydrochlorothiazide 25 mg daily.
Contraindications
- Anuria
- Hypersensitivity to sulfonamide-derived drugs or irbesartan
- Pregnancy
Side Effects
- Dizziness
- Fatigue
- Musculoskeletal pain
- Nausea/vomiting
- Hyperkalemia (irbesartan)
- Hypokalemia (hydrochlorothiazide)
- Increased blood urea nitrogen
- Cough (less common than with ACE inhibitors)
- Photosensitivity
Interactions
- Lithium (increased lithium toxicity)
- NSAIDs (reduced antihypertensive effect, risk of renal impairment)
- Potassium supplements/potassium-sparing diuretics (risk of hyperkalemia)
- Other antihypertensives (additive effects)
- Cholestyramine/colestipol (reduced absorption of hydrochlorothiazide)
- Alcohol/barbiturates/narcotics (potentiated orthostatic hypotension)