Angiotensin receptor blockers (ARBs)

3D molecular model of Candesartan

ARBs treat heart failure and high blood pressure and may be prescribed following a heart attack. Senior Cardiac Nurse Christopher Allen gets the lowdown from Dr Mark Pucci.

Angiotensin receptor blockers (ARBs), also known as angiotensin II receptor antagonists, are used to treat high blood pressure and heart failure. They are also used for chronic kidney disease and prescribed following a heart attack. They include valsartan, losartan and candesartan. If the name of a medicine ends in ‘sartan’, it is an ARB.

What are ARBs and how do they work?

ARBs reduce the action of the hormone angiotensin II. This hormone has a powerful constricting effect on blood vessels, increasing blood pressure. Angiotensin II also stimulates salt and water retention in the body, which further increases blood pressure.

ARBs work by blocking receptors that the hormone acts on, specifically AT1 receptors, which are found in the heart, blood vessels and kidneys. Blocking the action of angiotensin II helps to lower blood pressure and prevent damage to the heart and kidneys.

Why have I been given this medication?

ARBs are commonly used for high blood pressure (hypertension), chronic kidney disease, and following a heart attack to limit further damage.

They’re also used in people with heart failure. Because they reduce inflammation, ARBs are also useful in patients with high blood pressure and non-alcoholic fatty liver disease, to prevent liver inflammation.

Numerous clinical trials have shown that ARBs lower the risk of heart attack and stroke, and slow down damage to the kidneys in people with reduced kidney function. They also reduce hospital admissions and improve life expectancy for people with heart failure.

Are ARBs and ACE inhibitors the same?

ACE inhibitors have similar properties to ARBs, and the drugs are often used interchangeably. ACE inhibitors also reduce the effect of angiotensin, but by decreasing the amount your body makes, rather than blocking receptors.

Both are first-choice drugs for younger, non-African-Caribbean patients with high blood pressure. ACE inhibitors can frequently cause a dry cough. If this doesn't go away, patients are often given an ARB instead.

How long will I take them?

Most people take these drugs long term, often for life. Some patients wrongly imagine that once their blood pressure is controlled, they can stop taking their tablets. Unfortunately, this is rarely the case: high blood pressure will return once the medication is stopped.

It may be necessary to stop taking the medication temporarily, for example, if you have severe diarrhoea or vomiting. In this scenario, you may become dehydrated and ARBs could then upset the kidneys. You should urgently consult your doctor.

When should I take them?

ARBs tend to be taken once a day in the morning, but they can be taken any time of day. If you’ve been asked to wear a 24-hour blood pressure monitor, you may be advised by a specialist to take your medicine at a particular time of day to suit your blood pressure pattern. Read the leaflet that accompanies the medicine before you start taking it.

Do other medications interact with ARBs?

Taking ARBs with ACE inhibitors is not recommended, due to increased risk of acute kidney injury and high potassium levels, which are linked to abnormal heart rhythms.

Patients with high blood pressure or heart failure often need a combination of medications. The risk of high potassium levels in the blood (hyperkalaemia) increases if you are taking other drugs that can raise potassium levels. This includes some painkillers, like ibuprofen and naproxen, and potassium-sparing diuretics (a type of mild water tablet which stops too much potassium being lost in your urine) such as spironolactone, eplerenone or amiloride.

Speak to your doctor if this is the case; you may need regular blood tests to monitor your potassium levels.

Are there any foods or drinks to avoid?

Salt substitutes such as ‘LoSalt’ contain potassium chloride, which can cause high blood potassium levels. Speak to your doctor if you’re using this. A regular high alcohol intake can worsen high blood pressure, which could counteract the effect of your medication. However, binge drinking can lower blood pressure temporarily. If you’re taking blood pressure medication, this could cause light-headedness and even fainting. Keep your alcohol intake to a minimum.

Are there any side effects?

ARBs are generally well-tolerated but, as with any drug, they can cause unwanted effects, including dizziness, headache and fatigue. These may improve after a few days.

After you start the drug, you’ll need another blood-test to check your kidney function. In some cases, ARBs can upset the kidneys, especially if the blood vessels to your kidneys are narrowed (renal artery stenosis).

Is there anyone who shouldn’t take ARBs?

Avoid them if you are pregnant or trying to get pregnant, due to toxic effects on the foetus. If you are a woman of childbearing age, ARBs can be used safely alongside appropriate contraception.

If you become pregnant, the medication should be stopped as soon as possible under the guidance of your doctor.

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