Olmesartan with hydrochlorothiazide

How it works

Olmesartan blocks the angiotensin-II type-1 receptor to reduce vasoconstriction and sodium retention, while hydrochlorothiazide enhances renal excretion of sodium and water; the diuretic-driven activation of the renin-angiotensin system is offset by the receptor blocker.

Prescribing in practice

• Avoid in pregnancy because the angiotensin-receptor-blocker component is foetotoxic; advise effective contraception and review before conception.
• The thiazide can precipitate hyponatraemia, hypokalaemia, hyperuricaemia with gout and dehydration, and may unmask or worsen glucose intolerance.
• Olmesartan carries a rare risk of severe sprue-like enteropathy, and the combination can cause hypotension and renal impairment, especially in volume-depleted or elderly patients.

Monitoring

Monitor blood pressure, renal function and serum electrolytes including sodium, potassium and where relevant urate after initiation and dose adjustment.

Counselling the patient

• Report persistent severe diarrhoea or unexplained weight loss, which can rarely be linked to this medicine.
• Stay adequately hydrated, particularly in hot weather or intercurrent illness.
• Inform your doctor at once if you become pregnant.

Evidence & guidelines

Adding a thiazide to an angiotensin-receptor blocker is a recognised step in NICE hypertension management, and fixed-dose combinations support adherence and blood-pressure control.