ARB + thiazide Pregnancy: Contraindicated during the second and third trimesters; angiotensin II receptor antagonists are not recommended in the first trimester and, because of the hydrochlorothiazide component, the combination is also not recommended in the first trimester. Switch to a suitable alternative in advance of a planned pregnancy and stop immediately when pregnancy is diagnosed. Breast-feeding: not recommended, especially while nursing a newborn or preterm infant.

Irbesartan with hydrochlorothiazide

Brand names: CoAprovel

This is a fixed-dose combination of irbesartan, an angiotensin-II receptor blocker (ARB), with hydrochlorothiazide, a thiazide diuretic, used to treat essential hypertension in patients not adequately controlled on either component alone.

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: One tablet daily; irbesartan/hydrochlorothiazide 150 mg/12.5 mg in patients whose blood pressure is not adequately controlled with hydrochlorothiazide or irbesartan 150 mg alone

Route: Oral, with or without food

Frequency: Once daily

Max: 300 mg irbesartan / 25 mg hydrochlorothiazide once daily — higher doses are not recommended

Source is the fixed-combination SPC (CoAprovel 150 mg/12.5 mg). Step-up sequence per §4.2: 150 mg/12.5 mg for patients not adequately controlled on hydrochlorothiazide or irbesartan 150 mg alone; 300 mg/12.5 mg for patients insufficiently controlled by irbesartan 300 mg or by 150 mg/12.5 mg; 300 mg/25 mg for patients insufficiently controlled by 300 mg/12.5 mg. Dose titration with the individual components may be recommended; when clinically appropriate a direct change from monotherapy to the fixed combination may be considered. May be administered with another antihypertensive medicinal product when necessary. Hepatic impairment: not indicated in severe hepatic impairment; thiazides should be used with caution in impaired hepatic function; no dosage adjustment in mild to moderate hepatic impairment. Older people: no dosage adjustment necessary. Paediatric: not recommended in children and adolescents — safety and efficacy have not been established and no data are available.

Dose adjustments

Renal

Not recommended in severe renal dysfunction (creatinine clearance <30 ml/min) because of the hydrochlorothiazide component — loop diuretics are preferred in this population. No dosage adjustment is necessary where creatinine clearance is ≥30 ml/min, but in mild to moderate renal impairment (creatinine clearance ≥30 but <60 ml/min) the fixed dose combination should be administered with caution. Periodic monitoring of potassium, creatinine and uric acid is recommended in impaired renal function.

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.

Contraindications

Hypersensitivity to the active substances, to any of the excipients, or to other sulfonamide-derived substances (hydrochlorothiazide is sulfonamide-derived)
Second and third trimesters of pregnancy
Severe renal impairment (creatinine clearance <30 ml/min)
Refractory hypokalaemia; hypercalcaemia
Severe hepatic impairment, biliary cirrhosis and cholestasis
Concomitant use with aliskiren-containing products in patients with diabetes mellitus or renal impairment (GFR <60 ml/min/1.73 m²)

Side effects

Common: dizziness
Common: fatigue
Common: nausea/vomiting
Common: abnormal urination; increases in blood urea nitrogen, creatinine and creatine kinase
Uncommon: syncope, hypotension, tachycardia, oedema; decreases in serum potassium and sodium
Not known: hyperkalaemia; hypersensitivity reactions such as angioedema, rash and urticaria; impaired renal function including isolated cases of renal failure in patients at risk

Interactions

Aliskiren-containing products — contraindicated in diabetes mellitus or renal impairment (§4.3)
ACE inhibitors, other angiotensin II receptor blockers or aliskiren (dual RAAS blockade) — increased risk of hypotension, hyperkalaemia and decreased renal function including acute renal failure; not recommended, and must not be used concomitantly in patients with diabetic nephropathy (§4.4)
Vigorous diuretic therapy, dietary salt restriction, diarrhoea or vomiting — correct volume/sodium depletion before initiating to avoid symptomatic hypotension (§4.4)
NOTE: SPC §4.5 was not captured in the fetched extract — clinician to review the full interactions section

Clinical monograph

How it works

Irbesartan blocks the angiotensin-II type 1 receptor to cause vasodilatation and reduce aldosterone-driven sodium retention, while hydrochlorothiazide promotes renal sodium and water excretion; the two actions lower blood pressure additively.

Prescribing in practice

The combination is contraindicated in pregnancy because the ARB component can cause serious foetal harm, and it should be stopped as soon as pregnancy is recognised.
Avoid concurrent use with another renin-angiotensin system blocker (dual blockade), and use caution combining with potassium-sparing agents or potassium supplements as the net potassium effect is unpredictable.
Hydrochlorothiazide can cause hyponatraemia, hypokalaemia and gout, and has been associated with photosensitivity and a small increased risk of non-melanoma skin cancer.

Monitoring

Monitor blood pressure, renal function and serum electrolytes (sodium and potassium) before starting and during treatment, particularly after dose changes or intercurrent illness.

Counselling the patient

Do not take this medicine if you are or might become pregnant; tell your doctor straight away if you conceive.
Use sun protection, as the diuretic component can make your skin more sensitive to sunlight.
Report dizziness, muscle cramps or excessive thirst, which may indicate salt or water imbalance.

Evidence & guidelines

Use of an ARB combined with a thiazide diuretic for blood pressure not controlled on monotherapy is consistent with NICE hypertension guidance and established combination-therapy trial evidence.

Reference: 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.

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