Angiotensin II receptor blockers (ARBs)
Therapeutic actions
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.
Clinical pharmacology
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).
| 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 |
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
Adverse effects of angiotensin receptor blockers (ARBs) can affect various systems in the body.
- CNS effects include headache, dizziness, syncope, muscle weakness, fatigue, and depression.
- Cardiovascular effects primarily consist of hypotension.
- Dermatologic reactions may manifest as rash, inflammation, urticaria, pruritus, alopecia, and dry skin.
- Gastrointestinal side effects can include diarrhea, abdominal pain, nausea, and constipation.
- Respiratory issues may present as upper respiratory infection (URI) symptoms, cough, and sinus disorders. Additionally, other potential concerns include cancer in preclinical studies, urinary tract infections (UTIs), and pain.
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 medications without regard to meals, and do not stop taking them without consulting your health care provider. While using these drugs, it is essential to use a barrier method of birth control; if you become pregnant or wish to become pregnant, consult your physician. You may experience side effects such as dizziness, so it is advisable to avoid driving a car or performing hazardous tasks during this time. Other possible side effects include nausea and abdominal pain; maintaining proper nutrition is important, so consider consulting a dietitian to help manage your dietary needs. Additionally, be aware of symptoms of upper respiratory tract or urinary tract infections, and if you experience a cough that becomes uncomfortable, do not self-medicate—consult your health care provider. It is crucial to report any occurrences of fever, chills, dizziness, or pregnancy to your healthcare provider.
References
- Gallo G, Volpe M, Rubattu S. Angiotensin Receptor Blockers in the Management of Hypertension: A Real-World Perspective and Current Recommendations. Vasc Health Risk Manag. 2022;18:507-515.
- Hill, R.D. and Vaidya, P.N. (2020). Angiotensin II Receptor Blockers (ARB, ARb). [online] PubMed. Available at: https://www.ncbi.nlm.nih.gov/books/NBK537027.
- Townsend RR. Major side effects of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers. UpToDate www.uptodate.com.
