Angiotensin II receptor blockers

Angiotensin II receptor blockers

Angiotensin II receptor blockers (ARBs) lower blood pressure by blocking the vasoconstrictive effects of angiotensin II. Specific drugs include:

·                 candesartan cilexetil

·                 eprosartan

·                 irbesartan

·                 losartan

·                 olmesartan

·                 telmisartan

·                 valsartan.

Pharmacokinetics

ARBs have varying pharmacokinetic properties and all are highly bound to plasma proteins.

Pharmacodynamics

ARBs act by interfering with the renin-angiotensin-aldosterone system. Specifically, these drugs block the binding of angiotensin to the AT₁ receptor. This prevents angiotensin II from exerting its vasoconstricting properties and from promoting the excretion of aldosterone. Both of these actions result in lowered blood pres-sure.

ARBs don’t inhibit the conversion of angiotensin I to an-giotensin II, nor do they cause a breakdown in bradykinin (a va-sodilator).

Pharmacotherapeutics

ARBs may be used alone or in combination with other drugs such as a diuretic. Valsartan may also be used as an alternative to an ACE inhibitor or for the management of heart failure. Because irbesartan and losartan protect the renal system, they’re often pre-scribed for patients with type 2 diabetes. Losartan is also used to reduce the risk of stroke in high-risk patients with hypertension and left ventricular hypertrophy. (See Adverse reactions to ARBs.)

Drug interactions

ARBs can interact with other drugs in various ways.

§    When losartan is taken with fluconazole, an increased blood lev-el of losartan may result, leading to hypotension.

§    NSAIDs reduce the antihypertensive effects of ARBs.

§    Rifampin may increase metabolism of losartan and decrease its antihypertensive effect.

§    Candesartan may increase blood levels of lithium, leading to lithium toxicity.

§    When digoxin is taken with telmisartan, an increased blood level of digoxin may occur, possibly leading to digoxin toxicity.

§    Potassium supplements may increase the risk of hyperkalemia when used with ARBs.