- What are angiotensin II receptor blockers?
- How do they work?
- What are they used for?
- Side effects
Angiotensin II receptor blockers (ARBs) are a class of drugs used to treat hypertension. Examples of common ARBs include candestartan, lsartan and telmisartan. ARBs are believed to reduce blood pressure to the same extent as other antihypertensive drug classes such as, β-blockers and angiotensin converting enzyme inhibitors (ACEi).
Angiotensin II receptor blockers bind to the Angiotensin I Receptor (AT1) and prevent the effects of angiotensin II being mediated. AT1 mediate most of the effects of angiotensin II and those that are mediated by angiotensin receptor II are not yet established. ARBs bind specifically to the AT1 receptor to reduce hypertension. They have a highly specific affinity for AT1. The biological effects of angiotensin II are contraction of blood vessels, aldosterone release, sympathetic nerve stimulation and cell growth. These effects are inhibited by ARBs.
ARBs are used to treat hypertension and are especially used by those who cannot tolerate ACEi. They are also used to slow the worsening of renal disease in type II diabetics. The maximum antihypertensive effect usually occurs around 4-6 weeks after treatment has been started.
Common side effects include:
Infrequent side effects include:
Rare side effects include:
Several pre-existing conditions may restrict the use of ARBs. If not noted they could lead to serious damage or lead to the development of other conditions.
Hypotension is when you have a lower blood pressure than normal. There is an increased risk of low blood pressure when taking ARBs and if you have a reduced volume or sodium level or have either aortic stenosis or mitral valve stenosis.
Hyperkalaemia is when there is an excess of potassium in the blood. This can lead to potentially fatal arrythmias of the heart. When taking ARBs there is an increased risk of hyperkalaemia if you are also taking drugs that increase potassium concentrations (eg cyclosporin). It is advised that if taking drugs which increase potassium concentrations to either prevent use by switching to another drug or to monitor potassium levels carefully.
Problems with kidneys can also lead to increased risk of hyperkalaemia. As a result, it is advised that a lower starting dose should be used and monitoring of potassium levels should also occur.
Primary hyperaldosteronism or Conn’s Syndrome is the excessive production of aldosterone occurring independently of the renin angiotensin system. If the you have this condition then it can reduce the antihypertensive effect of the drug.
ARBs should be avoided if pregnant as it may adversely effect the developing baby. It is recommended that an alternative antihypertensive should be used instead. ARBs are part of the ADEC category D.
Guidelines regarding breastfeeding and ARBs use have not been produced as yet.
NSAIDs like cyclooxgenase-2 inhibitors can reduce the antihypertensive effect.
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- Part of Chapter 5.2- Adrenal imaging, Primary hyperaldosteronism (Conn’s syndrome) In: Wass JAH, Shalet SM, Gale E et al. editors. Oxford Textbook of Endocrinology and Diabetes: Oxford University Press; 2002
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