Last reviewed 2026-04-20 · How we verify

olmesartan medoxomil-hydrochlorothiazide (OLMESARTAN)

Olmesartan works by blocking the action of a hormone that causes blood vessels to constrict, allowing blood vessels to relax and blood pressure to decrease.

Olmesartan medoxomil-hydrochlorothiazide (olmesartan) is a thiazide diuretic small molecule medication. It is used to treat hypertension, cardiovascular events, strokes, myocardial infarctions, diabetes, hyperlipidemia, angina, and heart failure. Originally developed by Macleods Pharms Ltd, it is now owned by Cosette and has been FDA-approved since 2019. As an off-patent medication, it is available from multiple generic manufacturers. Key safety considerations include its potential effects on electrolyte levels and renal function.

At a glance

Mechanism of action

Olmesartan medoxomil Angiotensin II is formed from angiotensin I in a reaction catalyzed by angiotensin converting enzyme (ACE, kininase II). Angiotensin II is the principal pressor agent of the renin-angiotensin system, with effects that include vasoconstriction, stimulation of synthesis and release of aldosterone, cardiac stimulation and renal reabsorption of sodium. Olmesartan blocks the vasoconstrictor effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT 1 receptor in vascular smooth muscle. Its action is, therefore, independent of the pathways for angiotensin II synthesis. An AT 2 receptor is found also in many tissues, but this receptor is not known to be associated with cardiovascular homeostasis. Olmesartan has more than a 12,500-fold greater affinity for the AT 1 receptor than for the AT 2 receptor. Blockade of the angiotensin II receptor inhibits the negative regulatory feedback of angiotensin II on renin secretion

Approved indications

• Hypertension

Boxed warnings

• WARNING: FETAL TOXICITY When pregnancy is detected, discontinue olmesartan medoxomil and hydrochlorothiazide as soon as possible [see Warnings and Precautions (5.1) ] . Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus [see Warnings and Precautions (5.1) ] . WARNING: FETAL TOXICITY See full prescribing information for complete boxed warning. When pregnancy is detected, discontinue olmesartan medoxomil and hydrochlorothiazide as soon as possible ( 5.1 ). Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus ( 5.1 ).

Common side effects

• Nausea
• Dizziness
• Upper Respiratory Infection
• Hyperuricemia
• Chest pain
• Back pain
• Peripheral edema
• Vertigo
• Abdominal pain
• Dyspepsia
• Gastroenteritis
• Diarrhea

Drug interactions

• Lithium
• NSAIDs
• NSAIDs
• Thiazide diuretics
• Colesevelam hydrochloride
• Antidiabetic drugs
• Cholestyramine and colestipol
• Aliskiren
• ACE inhibitors
• Other RAS inhibitors
• Bile acid sequestering agents
• Ion exchange resins

Key clinical trials

• Efficacy and Safety of Olmesartan Associated With Chlorthalidone Versus Benicar HCT® in Essential Hypertension Control (PHASE3)
• Efficacy and Safety of Olmesartan Associated With Chlorthalidone in Essential Arterial Hypertension Control (PHASE3)
• Association of Angiotensin-Converting Enzyme Inhibitors and Angiotensin Receptor Blockers With Post-Stroke Pneumonia: A Real-World Retrospective Cohort Study
• Zilebesiran as Add-on Therapy in Patients With Hypertension Not Adequately Controlled by a Standard of Care Antihypertensive Medication (KARDIA-2) (PHASE2)
• Study to Evaluate the Effect of Improving Systolic BP and LDL-C Compared to Conventional Treatments and the Convenience of Taking Medication of Olostar Tab
• Reduction Efficacy of OLOMAX for Blood Pressure and Low-density Lipoprotein Cholesterol in Hypertensive Patients With Dyslipidemia
• Effect of Sacubitril/Valsartan on Cardiac Function in Hypertensive Patients Stratified by BMI: A Real World Study
• Fixed-dose Combination of an Angiotensin Receptor Blocker and Thiazide Diuretic for Essential Hypertension (PHASE3)

Primary sources

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