Angiotensin II receptor blockers
How they work
Angiotensin causes blood vessels to constrict, which drives the blood pressure up, and also
stimulates the release of aldosterone which promotes sodium retention (and therefore water retention) again increasing blood pressure.
ARB's work by blocking the binding of Angiotensin II to its membrane bound type-1 receptor subtype on the arteries, displacing Angiotensin II. These drugs therefore function as selective blockers. (The type 2- receptor subtype are not believed to be involved in cardiovascular homeostasis so hypertensive drugs are not made to target this type).
When are ARB's used?
ARB's are also suitable to be the first line agents to treat hypertension and can be used for patients who develop a chronic cough when using ACE inhibitors, ARB's are thought to have all the same advantages as the ACE inhibitors.
How to take ARB's
- May be taken by mouth in an oral tablet
- Do not take if pregnant, as particularly harmful to the fetus if used in the last 6 months of pregnancy.
Interactions with other drugs:
ARB's may increase blood levels of potassium, so interactions with other drugs that increase potassium also may result in excess potassium levels and lead to cardiac arrhythmias.
ARB's may increase the blood concentration of lithium, and so thus lead to lithium toxicity due to the increased amount of lithium reabsorbed in the kidney tubules.
Combination of ACE inhibitor and ARB's are often used to treat patients who have hypertension in addition to a certain second disease- this works best in controlling the hypertension and also has a benefit on the second disease.
Examples of ARB's (Brand names given in brackets)
- Iosartan (Cozaar)
- Irebesartan (Avapro)
- Valsartan (Diovan)
- Candesartan (Atacand)
- Olmesartan (Benicar)
- Telmisartan (Micardis)
- Eprosartan (Teveten)
Very few side effects, but some reports of feeling dizzy
Effectiveness
- Not suitable for those of African-Caribbean origin
Angiotensin II image courtesy of CV Pharmacology:
