Olmesartan

Generic Name: Olmesartan Medoxomil

Brand Names: Benicar

Olmesartan is an angiotensin receptor blocker (ARB) used to treat high blood pressure and protect the kidneys.

CardiovascularARB

Drug Class

Angiotensin II Receptor Blocker (ARB)

Pregnancy

Category D — Drugs acting on the renin-angiotensin system during the second and third trimesters cause fetal renal dysfunction, oligohydramnios, skull hypoplasia, and death. Discontinue olmesartan as soon as pregnancy is detected. FDA Boxed Warning applies.

Available Forms

Oral tablet (5 mg, 20 mg, 40 mg)

What It's Used For

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

Dosage Quick Reference

These are general dosage guidelines. Your doctor will determine the appropriate dose for your specific situation.

Condition	Starting Dose	Maintenance Dose
Hypertension (adults)	20 mg once daily	20–40 mg once daily; max 40 mg/day
Hypertension (children 6–16 years, 20 to < 35 kg)	10 mg once daily	10–20 mg once daily
Hypertension (children 6–16 years, >= 35 kg)	20 mg once daily	20–40 mg once daily

Side Effects

Common Side Effects:

Dizziness
Diarrhea
Upper respiratory infection
Headache
Back pain
Fatigue

Serious Side Effects (seek immediate medical attention):

Severe, chronic diarrhea with weight loss (sprue-like enteropathy)
Signs of high potassium (weakness, slow heartbeat)
Signs of kidney problems (decreased urination, swelling)
Severe hypotension (fainting)
Angioedema (swelling of face, lips, tongue, throat)

Drug Interactions

Olmesartan has clinically relevant interactions primarily related to its effects on the renin-angiotensin-aldosterone system and renal hemodynamics.

ACE inhibitors (e.g., lisinopril, enalapril) or aliskiren: Dual renin-angiotensin-aldosterone system (RAAS) blockade increases the risk of hyperkalemia, hypotension, and acute kidney injury. Avoid concurrent use, especially in patients with diabetes or renal impairment (GFR < 60 mL/min).
Potassium-sparing diuretics or potassium supplements (e.g., spironolactone, eplerenone, potassium chloride): Olmesartan reduces aldosterone secretion, raising serum potassium. Additive hyperkalemia risk when combined with other potassium-elevating agents. Monitor serum potassium regularly.
NSAIDs (e.g., ibuprofen, naproxen, celecoxib): NSAIDs blunt the antihypertensive effect of ARBs and may further impair renal function, particularly in volume-depleted or elderly patients. Use the lowest effective NSAID dose for the shortest duration.
Lithium: ARBs reduce lithium renal clearance, increasing the risk of lithium toxicity (tremor, confusion, renal damage). Monitor lithium levels closely if co-administration is necessary.
Colesevelam: This bile acid sequestrant reduces olmesartan absorption. Administer olmesartan at least 4 hours before colesevelam.

Additional Information

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.

Learn more at MedlinePlus

Frequently Asked Questions

A measurable reduction in blood pressure typically occurs within 1 to 2 weeks of starting olmesartan, but the full antihypertensive effect may take 4 to 8 weeks to develop. Your doctor will likely recheck your blood pressure after about 2 to 4 weeks to determine whether a dose adjustment is needed.

Yes. Olmesartan is an ARB, which works at a different point in the renin-angiotensin system than ACE inhibitors. ARBs do not inhibit the breakdown of bradykinin — the mechanism responsible for the persistent dry cough that affects 5 to 20 percent of patients on ACE inhibitors. Angioedema is also less common with ARBs, though it can still rarely occur.

A rare but notable adverse effect unique to olmesartan is sprue-like enteropathy, a condition involving chronic severe diarrhea, weight loss, and villous atrophy of the small intestine that may develop months to years after starting the drug. Symptoms typically resolve after discontinuation. If you experience unexplained chronic diarrhea, report it to your doctor promptly.

You do not need to eliminate potassium-rich foods, but avoid excessive intake (large amounts of bananas, oranges, potatoes, or salt substitutes containing potassium chloride) and do not take potassium supplements without your doctor approval. Olmesartan can raise serum potassium levels, and routine blood monitoring helps detect any clinically significant increase.

Moderate alcohol consumption may enhance the blood-pressure-lowering effect of olmesartan, potentially causing dizziness or lightheadedness — especially when standing up quickly. If you choose to drink, do so in moderation and be cautious about positional changes. Discuss your alcohol intake honestly with your doctor.

Questions to Ask Your Doctor

Consider discussing these topics at your next appointment:

✓Is my kidney function adequate to start olmesartan, and how often will you monitor it?
✓Should I be checking my blood pressure at home, and what readings should prompt me to call you?
✓Are any of my other medications known to interact with olmesartan?
✓What are the warning signs that my potassium level might be too high?
✓If olmesartan alone is not enough to control my blood pressure, what would the next step be?

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Related Health Conditions

This medication is commonly used to treat or manage the following conditions:

Portal Hypertension

Portal hypertension, an elevated pressure in the portal vein due to blockage often from cirrhosis or other pre-hepatic causes, can lead to serious complications like bleeding and ascites.

Learn More

Secondary Pulmonary Hypertension

Secondary pulmonary hypertension, unlike its primary form, arises from underlying conditions such as heart/lung disease, blood clots, or connective tissue disorders, increasing lung artery pressure.

Learn More

Medical Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with your healthcare provider before starting, stopping, or changing any medication. Your doctor can provide personalized recommendations based on your specific health condition and medical history.