Irbesartan

• Hypertension
• Diabetic Nephropathy
• Cardiovascular Protection
• Kidney Disease in Diabetes

Irbesartan is an angiotensin II receptor blocker (ARB) used for the treatment of hypertension and diabetic nephropathy in patients with type 2 diabetes. This medication provides effective cardiovascular and renal protection by blocking the effects of angiotensin II on its receptor.

Mechanism of Action

Irbesartan selectively blocks the binding of angiotensin II to the AT1 receptor found in vascular smooth muscle, adrenal glands, kidneys, and other tissues. Angiotensin II is a potent vasoconstrictor and stimulates aldosterone secretion. By blocking the AT1 receptor, irbesartan causes vasodilation, reduces aldosterone release, and decreases sodium and water retention, resulting in lower blood pressure. Unlike ACE inhibitors, ARBs do not affect bradykinin metabolism, avoiding the cough associated with ACE inhibitors. In diabetic nephropathy, irbesartan reduces intraglomerular pressure and proteinuria, slowing progression of kidney disease.

Available Formulations

Irbesartan is available as oral tablets in 75 mg, 150 mg, and 300 mg strengths. It is also available in combination with hydrochlorothiazide (Avalide) for enhanced blood pressure control. The tablets can be taken with or without food. Generic formulations are widely available.

Medical Uses

Irbesartan is FDA-approved for the treatment of hypertension (alone or in combination with other antihypertensives) and for the treatment of diabetic nephropathy in patients with type 2 diabetes and hypertension (characterized by an elevated serum creatinine and proteinuria ≥300 mg/day). The IDNT and IRMA-2 trials demonstrated significant reductions in the progression of nephropathy and proteinuria in diabetic patients.

Dosing Guidelines

For hypertension, the recommended starting dose is 150 mg once daily; the dose may be increased to 300 mg once daily if needed. For diabetic nephropathy, the target maintenance dose is 300 mg once daily. Volume-depleted patients may be started at 75 mg. Irbesartan may be administered with other antihypertensive agents. No dose titration is required for most patients. The antihypertensive effect is usually apparent within 1-2 weeks, with maximal effect by 4-6 weeks.

Important Safety Information

Irbesartan carries a boxed warning regarding fetal toxicity. When pregnancy is detected, irbesartan should be discontinued immediately. Drugs that act on the renin-angiotensin system can cause injury and death to the developing fetus. Hypotension may occur, especially in volume-depleted patients. Hyperkalemia may develop, particularly in patients with renal impairment, diabetes, or those taking potassium supplements or potassium-sparing diuretics. Changes in renal function, including acute renal failure, may occur, especially in patients with renal artery stenosis.

Drug Interactions

Dual blockade of the renin-angiotensin system with ACE inhibitors, ARBs, and/or aliskiren increases risks of hypotension, hyperkalemia, and renal impairment; avoid combination. NSAIDs may reduce the antihypertensive effect and worsen renal function. Potassium supplements and potassium-sparing diuretics may increase hyperkalemia risk. Lithium levels may increase; monitoring is recommended. No significant CYP450 interactions occur.

Special Populations

Irbesartan is contraindicated during pregnancy and should be discontinued when pregnancy is detected. It is unknown whether irbesartan is excreted in human breast milk; breastfeeding is not recommended. Safety and efficacy have not been established in pediatric patients. Elderly patients do not require dose adjustment. No dose adjustment is needed for mild to moderate renal impairment, though close monitoring is advised. In severe renal impairment, use with caution. No dose adjustment is needed for hepatic impairment.