Angiotensin II receptor blockers (ARBs)

byAbdelwahab Ward, BS Pharm, PharmD - last updated
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THERAPEUTIC ACTIONS ã…¡ ARBs selectively block the binding of angiotensin II to specific tissue receptors found in the vascular smooth muscle and adrenal gland. This action blocks the vasoconstriction effect of the renin-angiotensin system as well as the release of aldosterone leading to decreased BP; may block vessel remodeling that occurs in hypertension and contributes to the development of atherosclerosis.

         Indications. Treatment of hypertension, alone or in combination with other antihypertensives, nephropathy in type 2 diabetes (losartan, irbesartan), treatment of heart failure in patients resistant to ACE inhibitors (valsartan) and reduction in the risk of stroke in patients with hypertension and left ventricular hypertrophy (losartan).

CONTRAINDICATIONS

Contraindicated with hypersensitivity to any ARB, pregnancy (use during the second or third trimester can cause injury or even death to the fetus), lactation. Use cautiously with renal impairment, hypovolemia. Pregnancy category C (first trimester) and pregnancy category D (second and third trimesters).

ADVERSE EFFECTS

  • CNS: Headache, dizziness, syncope, muscle weakness, fatigue, depression.
  • CV: Hypotension.
  • Dermatologic: Rash, inflammation, urticaria, pruritus, alopecia, dry skin.
  • GI: Diarrhea, abdominal pain, nausea, constipation.
  • Respiratory: URI symptoms, cough, sinus disorders.
  • Other: Cancer in preclinical studies, UTIs, pain.

INTERACTIONS

Decreased effectiveness if combined with phenobarbital. Risk of increased lithium levels. Risk of hyperkalemia if combined with potassium-sparing diuretics, potassium supplements, salt substitutes, aliskiren.

CLINICAL CONSIDERATIONS

Black box warning; Ensure that patient is not pregnant before beginning therapy; suggest the use of barrier contraception; fetal injury and deaths have been reported. Administer without regard to meals. Find an alternative method of feeding infant if ARBs are given to a nursing mother. Depression of the renin-angiotensin system in infants is potentially very dangerous. Alert surgeon and mark on patient's chart that an ARB is being taken. The blockage of the renin-angiotensin system after surgery can produce problems. Hypotension may be reversed with volume expansion. If BP control does not reach desired levels, diuretics or other antihypertensives may be added to the drug regimen. Monitor patient's BP carefully. Monitor patient closely in situations that may cause a decrease in BP secondary to reduction in fluid volume-excessive perspiration, dehydration, vomiting, diarrhea-excessive hypotension can occur.

TEACHING POINTS

  • Take these drugs without regard to meals. Do not stop taking these drugs without consulting your health care provider.
  • Use a barrier method of birth control while using these drugs; if you become pregnant or desire to become pregnant, consult your physician.
  • You may experience these side effects: Dizziness (avoid driving a car or performing hazardous tasks); nausea, abdominal pain (proper nutrition is important; consult a dietitian to maintain nutrition); symptoms of upper respiratory tract or urinary tract infection, cough (do not self-medicate, consult your health care provider if this becomes uncomfortable).
  • Report fever, chills, dizziness, pregnancy.

MEDICATIONS

Table (1). Dosages of angiotensin II receptor antagonists
DRUG USUAL STARTING DOSAGE DOSING RANGE
Candesartan (Atacand) 16 mg once daily 8 to 32 mg once daily
Irbesartan (Avapro) 150 mg once daily 150 to 300 mg once daily
Losartan (Cozaar) 50 mg once daily 25 to 100 mg once daily
Telmisartan (Micardis) 40 mg once daily 20 to 80 mg once daily
Valsartan (Diovan) 80 mg once daily 80 to 320 mg once daily

REFERENCES

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