Mzantsi Medics

Angiotensin-2 Receptor blockers [ARBS]in South Afrika

The table below lists some ARBs are available in SA: [1]

Generic	Example
Candesartan https://umzantsimedics.com/drug-pics/#:~:text=Candesartan%20/%20Candesartan,receptor%20blocker%20(ARB).	Atacand Mylacand
Irbesartan https://umzantsimedics.com/drug-pics/#:~:text=Irbesartan,receptor%20blocker%20(ARB).	Irbewin Aprovel
Losartan https://umzantsimedics.com/drug-pics/#:~:text=Losartan%20/%20Losartan%20potassium,receptor%20blocker%20(ARB).	Lozaan Zartan Annin Rasol Ciplazar
Telmisartan https://umzantsimedics.com/drug-pics/#:~:text=Valsartan-,Telmisartan,-Amiloride%2DHydrochlorothiazide%20(Combo	Micardis Mizart Pritor Tesar
Valsartan https://umzantsimedics.com/drug-pics/#:~:text=receptor%20blocker%20(ARB).-,Valsartan,-Telmisartan	Diovan Tareg Regoval Migroben Valheft

The effects of Angiotensin-2 on the AT₁ receptors

It is important to know the effects of Angiotensin-2 on AT₁ receptors in order to understand mechanism of action of ARB’s. The table below shows the effects of angiotensin-2 on AT₁ receptors.

Organ	Effects of Angitensin-2 binding on AT1 receptors
Arterioles	– Vasoconstriction
Adrenal cortex	– Aldosterone secretion
Kidney	– Sodium (NaCl) and water (H2O) reabsorption (proximal CT) – Fibrosis
Heart	– Positive inotropy – Positive chronotropy – Hypertrophy – Fibrosis
Brain	– Antidiuretic hormone (Vasopressin) secretion – Thirst – Appetite for salt – SNS activation

Mechanism of action of ARBS

ARB’s selectively inhibit the binding of Angiotensin-2 on the AT₁ receptors. [2] [3] [4] This inhibition results in:

1. Less arteriolar vasoconstriction.
2. Reduced aldosterone secretion from adrenal cortex.
3. Reduced sodium and water reabsorption.

Indications for ARBs

The following are the indications for ARB’s: [5] [6]

1. Hypertension
2. Heart failure
3. Type 2 DM nephropathy.

References

1. Rossiter D, Blockman M, Barnes KI. South African Medicines Formulary. 14^th edition. Cape town: SAMA Health and Medical Publishing Group; 2022. C09, Agents Acting On the Renin-Angiotensin System; p.171-176. 
2. Brenner GM, Stevens CW. Pharmacology. 4^th edition. Philadelphia: Elsevier-Saunders; 2013. Chapter 8, Antihypertensive drugs; p.97.
3. Hill, R.D. and Vaidya, P.N. (2024b) “Angiotensin II receptor blockers (ARB),” in StatPearls. Treasure Island (FL): StatPearls Publishing.
4. Schmieder, R. (2005) “Mechanisms for the clinical benefits of angiotensin II receptor blockers,” American journal of hypertension, 18(5), pp. 720–730. Available at: https://doi.org/10.1016/j.amjhyper.2004.11.032.
5. No date a) Nih.gov. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC3212426/ (Accessed: October 27, 2024).
6. (No date b) Sciencedirect.com. Available at: https://www.sciencedirect.com/topics/nursing-and-health-professions/angiotensin-receptor-antagonist (Accessed: October 27, 2024).