Reviewed by MedNext Clinical Team
Angiotensin receptor blockers (ARBs), of which losartan was the first to be licensed, occupy a central role in the management of hypertension, heart failure, and diabetic nephropathy. They are often the drug of choice when ACE inhibitors are indicated but not tolerated [1].
When to Switch from ACE Inhibitor to ARB
ACE inhibitor-induced cough is the most common reason to switch to an ARB. The cough results from bradykinin accumulation — a consequence of ACE inhibition — and affects approximately 10–15% of patients, with higher rates in people of East Asian descent. Unlike ACE inhibitors, ARBs block the angiotensin II receptor directly without affecting bradykinin metabolism, and therefore do not cause cough [1].
Angioedema caused by ACE inhibitors is a contraindication to further use of that class. Cross-reactivity with ARBs is theoretically possible but rare, and ARBs are generally considered safe to use following ACE inhibitor-induced angioedema after careful risk-benefit assessment.
Renal Protection in Diabetic Nephropathy
ARBs have demonstrated renal protective effects in type 2 diabetic nephropathy independent of their blood pressure-lowering effects. Losartan, irbesartan, and others have been shown in landmark trials to reduce the progression of proteinuria and delay the onset of end-stage renal disease [1]. This makes ARBs (or ACE inhibitors) the preferred antihypertensive in patients with diabetes and microalbuminuria.
Hyperkalaemia Risk
ARBs reduce aldosterone secretion, which can cause potassium retention. Hyperkalaemia is a significant concern, particularly in patients with chronic kidney disease, those taking potassium-sparing diuretics, or those on concomitant NSAIDs. Renal function and electrolytes should be checked within 1–2 weeks of initiating or up-titrating an ARB, and monitored regularly thereafter.
Contraindications
ARBs are absolutely contraindicated in pregnancy due to their teratogenic effects on fetal renal development, causing oligohydramnios, renal failure, and fetal death. Women of childbearing age should use effective contraception, and ARBs must be stopped as soon as pregnancy is confirmed. Bilateral renal artery stenosis is also a contraindication, as with ACE inhibitors.
References
- Brenner BM, et al. Effects of losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathy. NEJM. 2001;345:861-869.