Irbesartan with hydrochlorothiazide

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.