Telmisartan with hydrochlorothiazide

How it works

Telmisartan blocks the angiotensin-II type-1 receptor to cause vasodilatation and reduce aldosterone-driven sodium retention, while hydrochlorothiazide inhibits the distal tubular sodium-chloride co-transporter to promote natriuresis, giving complementary blood-pressure lowering.

Prescribing in practice

• The combination is contraindicated in pregnancy because ARBs can cause serious foetal harm, so it must be stopped if pregnancy is planned or confirmed.
• Thiazide can cause hypokalaemia, hyponatraemia, hyperuricaemia and hyperglycaemia, while the ARB tends to raise potassium, so electrolyte balance and the interaction with NSAIDs (risk of acute kidney injury) need attention.
• It should not be combined with another renin-angiotensin blocker, and caution is needed in renal artery stenosis, gout and significant renal impairment.

Monitoring

Check renal function and serum electrolytes before starting and periodically during treatment, particularly after dose changes or intercurrent illness.

Counselling the patient

• Stop the tablet and seek advice if you become pregnant or are planning pregnancy.
• Report dizziness, cramps or weakness that may signal an electrolyte disturbance.
• Avoid regular over-the-counter anti-inflammatory painkillers unless advised.

Evidence & guidelines

ARB plus thiazide combinations are well-established antihypertensive therapy, and NICE guidance supports stepwise combination treatment to reach blood-pressure targets.