Olmesartan

• Hypertension in adults and children 6 years and older
• Alternative to ACE inhibitors in patients with cough
• Component of combination antihypertensive therapy

Olmesartan is an angiotensin II receptor blocker (ARB) used for the treatment of hypertension. By selectively blocking the AT1 receptor, it prevents the cardiovascular effects of angiotensin II while avoiding the cough that commonly occurs with ACE inhibitors, making it an important option for patients requiring renin-angiotensin-aldosterone system blockade.

Mechanism of Action

Olmesartan medoxomil is a prodrug that is rapidly converted to the active form, olmesartan, during absorption from the gastrointestinal tract. Olmesartan selectively blocks the binding of angiotensin II to the AT1 receptor in vascular smooth muscle and other tissues. This blockade prevents angiotensin II from causing vasoconstriction, aldosterone release, and sympathetic activation. Unlike ACE inhibitors, ARBs do not affect bradykinin metabolism, which explains the lower incidence of cough with this class of medications.

The AT2 receptor, which may have protective cardiovascular effects, is left unblocked by olmesartan. The increased circulating angiotensin II that results from AT1 blockade can stimulate AT2 receptors, potentially contributing to cardiovascular benefits.

Available Formulations

Olmesartan medoxomil (Benicar) is available as oral tablets in 5 mg, 20 mg, and 40 mg strengths. It is also available in fixed-dose combinations with hydrochlorothiazide (Benicar HCT), with amlodipine (Azor), and in a triple combination with both amlodipine and hydrochlorothiazide (Tribenzor) for patients requiring more intensive blood pressure control.

FDA-Approved Indications

Olmesartan is FDA-approved for the treatment of hypertension in adults and pediatric patients 6 years of age and older, either alone or in combination with other antihypertensive agents. While not specifically indicated for heart failure or diabetic nephropathy (unlike some other ARBs), it provides effective blood pressure control that is fundamental to cardiovascular protection.

Dosing Guidelines

For adults with hypertension, the recommended starting dose is 20 mg once daily when used as monotherapy. The dose may be increased to 40 mg once daily after 2 weeks if further blood pressure reduction is needed. For patients with possible volume depletion (those on diuretics or with reduced oral intake), consider starting at a lower dose. For pediatric patients 6 years and older, dosing is weight-based: 10 mg once daily for those weighing 20-35 kg, and 20 mg once daily for those weighing more than 35 kg.

Sprue-Like Enteropathy

A unique safety concern with olmesartan is the development of severe, chronic diarrhea with substantial weight loss, termed sprue-like enteropathy. This condition may develop months to years after starting therapy and is characterized by intestinal villous atrophy. Symptoms typically resolve after discontinuing olmesartan. If severe diarrhea develops during treatment, consider this diagnosis and discontinue the medication if no other etiology is identified.

Important Safety Considerations

Olmesartan carries a boxed warning for fetal toxicity; it should be discontinued immediately when pregnancy is detected. Hypotension may occur, especially in volume-depleted patients. Hyperkalemia can develop, particularly in patients with renal impairment or those taking potassium supplements. Renal function should be monitored in patients with renal artery stenosis, severe heart failure, or volume depletion.

Drug Interactions

NSAIDs may reduce the antihypertensive effect and increase renal impairment risk. Potassium supplements and potassium-sparing diuretics increase hyperkalemia risk. Avoid dual blockade of the renin-angiotensin system with ACE inhibitors or aliskiren (especially in diabetic patients) due to increased adverse effects. Lithium levels should be monitored if used concomitantly.

Special Populations

No dosage adjustment is needed for mild to moderate hepatic impairment or for renal impairment, although closer monitoring may be warranted. Use with caution in patients with bilateral renal artery stenosis. Olmesartan is contraindicated during pregnancy. Safety and efficacy have been established in pediatric patients 6 years of age and older for hypertension.

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