Angiotensin Receptor Blockers

Question 1

1) When are ARBs used?
2) Name the 3 ARB P-drugs.
3) Give the 4 common clinical indications for use of ARBs and state why they are used.

Answer 1

1) When ACE inhibitors are not tolerated due to cough.
2) Losartan, Vallarta’s and Candesartan.

3) HTN - first or second line treatment for HTN to reduce risk of stroke, MI or death from CV disease.
CHF - first line treatment for all grades to improve symptoms and prognosis.
IHD - to reduce risk of subsequent CV events such as stroke or MI.
Diabetic nephropathy and CKD with proteinuria - to reduce proteinuria and progression of nephropathy

Question 2

1) Give a basic mechanism of action of ARBs.
2) The effects of ARBs are similar to what other class of drugs?
3) What are the 3 main adverse effects of ARBs?
4) Who is most at risk of renal failure when using these drugs?

Answer 2

1) Block the action of Angiotensin II on AT1 receptors.
2) ACE inhibitors.
3) Hyperkalaemia, Hypotension and renal failure (see ACE inhibitors for reasons why).
4) Patients with renal artery stenosis.

Question 3

1) Why are ARBs less likely to cause a cough and angioedema?
2) Name 4 conditions when ARBs should not be used.
3) In what condition could the use of ARBs be valuable?
4) To what drugs are the contraindications of ARBs the same?

Answer 3

1) Because they do not inhibit ACE, so do not prevent the metabolism of bradykinins.

2) Pragnancy
Breastfeeding
Acute Kidney injury
Renal artery stenosis

3) Chronic kidney disease, but the effect on renal function should be monitored closely.
4) ACE inhibitors.

Question 4

What is the common choice of drug and dose when prescribing ARBs?

Answer 4

Losartan 12.5mg OD In heart failure.

Losartan 50mg OD for other indications.

Question 5

Why are ARBs preferable to ACE inhibitors in black people of African or Caribbean origin?

Answer 5

The incidence of angioedema related to ACE inhibitors is 5 times higher in this ethnic group. ARBs do not alter bradykinin levels and so are less likely to cause angioedema.

Question 6

Name the actions of Angiotensin II which are inhibited through ARBs binding to AT1 receptors.

Answer 6

Vasoconstriction, aldosterone release with salt and water retention, sympathetic nervous system stimulation, cell growth and proliferation.

Question 7

1) Where will candesartan activated and where is it eliminated?
2) What is Losartan eliminated by?
3) How is Vallarta’s eliminated?

Answer 7

1) Activated in the liver, eliminated by the kidneys.
2) Losartan and its active metabolite are eliminated by the kidneys.
3) Valsartan is eliminated in the bile and is unchanged.