Angiotensin II receptor antagonist (ARB) Pregnancy: Not recommended during the first trimester of pregnancy and CONTRAINDICATED during the second and third trimesters. Angiotensin II antagonist exposure in the second and third trimesters is known to induce human fetotoxicity (decreased renal function, oligohydramnios, skull ossification retardation) and neonatal toxicity (renal failure, hypotension, hyperkalaemia). Patients planning pregnancy should be changed to alternative antihypertensives with an established safety profile; when pregnancy is diagnosed, stop treatment immediately. If exposure occurred from the second trimester, ultrasound check of renal function and skull is recommended and infants should be closely observed for hypotension. Not recommended while breast-feeding - alternative treatments with better established safety profiles are preferable, especially while nursing a newborn or preterm infant (eMC 4.6).

Olmesartan medoxomil

Brand names: Olmetec

Olmesartan is an angiotensin-II receptor blocker (ARB) used for hypertension, including as an alternative when an ACE-inhibitor cough is troublesome. It is given as the prodrug olmesartan medoxomil.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Hypertension: 10 mg once daily initially; if blood pressure is not adequately controlled, increase to 20 mg once daily as the optimal dose

Route: Oral - swallow the tablet with a sufficient amount of fluid (e.g. one glass of water); the tablet should not be chewed. May be taken with or without food

Frequency: Once daily, at about the same time each day (for example at breakfast time)

Max: 40 mg daily

eMC SPC 4.2 (Olmesartan medoxomil 10 mg film-coated tablets). If additional blood pressure reduction is required beyond 20 mg once daily, the dose may be increased to a maximum of 40 mg daily, or hydrochlorothiazide therapy may be added. The antihypertensive effect is substantially present within 2 weeks of initiating therapy and is maximal by about 8 weeks - bear this in mind when considering changing the dose regimen. ELDERLY (65 years or over): no adjustment of dosage is generally required, but if up-titration to the maximum dose of 40 mg daily is required, blood pressure should be closely monitored (see also the renal impairment note). HEPATIC IMPAIRMENT: no adjustment for mild impairment; for moderate impairment an initial dose of 10 mg once daily is recommended and the maximum dose should not exceed 20 mg once daily, with close monitoring of blood pressure and renal function in patients already receiving diuretics and/or other antihypertensive agents; there is no experience in severe hepatic impairment so use is not recommended. Must not be used in patients with biliary obstruction (contraindicated). PAEDIATRIC (from SPC 4.2 - fixed and weight-banded doses, not a per-kg regimen, so not captured as a structured paedDose): children and adolescents from 6 to less than 18 years of age - recommended starting dose 10 mg once daily; if blood pressure is not adequately controlled the dose may be increased to 20 mg once daily; if additional blood pressure reduction is required, in children who weigh >= 35 kg the dose may be increased to a maximum of 40 mg, while in children who weigh < 35 kg the daily dose should not exceed 20 mg. Safety and efficacy in children aged 1 to 5 years have not yet been established and no recommendation on a posology can be made; olmesartan medoxomil should not be used in children below 1 year of age because of safety concerns and lack of data. Paediatric dosing must be confirmed against a children's formulary.

Dose adjustments

Renal

Mild to moderate renal impairment (creatinine clearance 20-60 mL/min): maximum dose 20 mg once daily, owing to limited experience of higher dosages in this patient group. Severe renal impairment (creatinine clearance < 20 mL/min): use is not recommended. When used in impaired renal function, periodic monitoring of serum potassium and creatinine is recommended. There is no experience in patients with a recent kidney transplant or with end-stage renal impairment (creatinine clearance < 12 mL/min) (eMC 4.2, 4.4).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

The recommended starting dose of olmesartan medoxomil and hydrochlorothiazide is 40/12.5 mg once daily in patients whose blood pressure is not adequately controlled with olmesartan monotherapy. Dose can be titrated up to 40 /25 mg if necessary. The recommended starting dose of olmesartan medoxomil and hydrochlorothiazide is 20/12.5 mg once daily in patients whose blood pressure is not adequately controlled with HCT monotherapy or who experience dose-limiting adverse reactions with hydrochlorothiazide. Dose can be titrated up to 40 /25 mg if necessary. Patients titrated to the individual components (olmesartan and hydrochlorothiazide) may instead receive the corresponding dose of olmesartan …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2026-01-19. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Second and third trimesters of pregnancy
Biliary obstruction
Concomitant use with aliskiren-containing products in patients with diabetes mellitus or renal impairment (GFR < 60 mL/min/1.73 m2)

Side effects

Common: headache (7.7%), influenza-like symptoms (4.0%), dizziness (3.7%), fatigue
Common: bronchitis, pharyngitis, cough, rhinitis
Common: gastroenteritis, diarrhoea, abdominal pain, nausea, dyspepsia; rare: intestinal angioedema; very rare: sprue-like enteropathy
Common: hypertriglyceridaemia, hyperuricaemia, raised hepatic enzymes, raised blood urea and creatine phosphokinase; rare: hyperkalaemia, raised blood creatinine
Common: arthritis, back pain, skeletal pain, haematuria, urinary tract infection, peripheral oedema, chest pain
Rare: hypotension, angioedema, acute renal failure, renal insufficiency; uncommon: anaphylactic reaction, thrombocytopenia, angina pectoris; not known: autoimmune hepatitis (latency of a few months to years, reversible after withdrawal)

Interactions

Aliskiren-containing products - contraindicated in patients with diabetes mellitus or renal impairment (GFR < 60 mL/min/1.73 m2); dual inhibition of the renin-angiotensin system increases the risk of renal impairment, hypotension and hyperkalaemia (eMC 4.3; US label 7.4)
Other medicinal products that may increase potassium levels - risk of hyperkalaemia, which may be fatal; increased in the elderly, in renal insufficiency, in diabetic patients and with intercurrent events (eMC 4.4; US label 7.1)
Lithium - increases in serum lithium concentrations and lithium toxicity reported; monitor serum lithium levels (US label 7.2)
NSAIDs including selective COX-2 inhibitors - reduced antihypertensive effect and increased risk of renal toxicity, particularly in elderly, volume-depleted or renally impaired patients (US label 7.3)
Colesevelam hydrochloride - consider administering olmesartan at least 4 hours before the colesevelam dose (US label 7.5)
NOTE: eMC 4.5 was not captured in this bundle - the entries above come from eMC 4.3/4.4 and, where marked, from the US label 7 (which is for the olmesartan/hydrochlorothiazide combination product). Clinician to review the full 4.5 before publication.

Clinical monograph

How it works

It selectively blocks the angiotensin II type 1 (AT1) receptor, preventing angiotensin II-mediated vasoconstriction and aldosterone secretion to lower blood pressure.

Prescribing in practice

It can rarely cause a severe sprue-like enteropathy (chronic diarrhoea with marked weight loss and intestinal villous atrophy), sometimes after months or years — investigate other causes and discontinue if no other cause is found, as symptoms resolve on stopping.
Avoid in pregnancy because of fetal toxicity; women planning pregnancy should be switched to an alternative.
Hyperkalaemia and reduced renal function can occur, especially with renal impairment, renal artery stenosis, or alongside potassium-sparing diuretics, potassium supplements or NSAIDs; symptomatic hypotension may occur in volume-depleted patients.

Monitoring

Check renal function, electrolytes (including potassium) and blood pressure before starting and after initiation or dose changes. Monitor blood pressure for response, and consider olmesartan as a cause in any patient who develops chronic diarrhoea and weight loss.

Counselling the patient

Report persistent or severe diarrhoea with weight loss, as the medicine may occasionally cause this and may need to be stopped.
Tell us at once if you become pregnant or are planning pregnancy, as this medicine must be stopped.
Avoid potassium-based salt substitutes and do not start potassium supplements unless advised.

Evidence & guidelines

ARBs are a guideline-recommended option for hypertension (NICE NG136); sprue-like enteropathy is an MHRA-recognised class warning for olmesartan.

Reference: MHRA Drug Safety Update; NICE NG136; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Myasthenia Gravis Activities of Daily Living (MG-ADL) Scale · Neuromuscular

Drugs

Pathways