How long should I discontinue losartan (angiotensin receptor blocker) before an aldosterone‑renin screening, and what alternative antihypertensive can I use during the washout period?

Discontinuation of Losartan Before Aldosterone-Renin Screening

Discontinue losartan for 2 weeks before aldosterone-renin ratio (ARR) screening for primary aldosteronism, and use non-dihydropyridine calcium channel blockers (verapamil or diltiazem), alpha-1 blockers (doxazosin), or hydralazine as alternative antihypertensives during the washout period. 1

Washout Duration

The 2025 Endocrine Society Clinical Practice Guideline explicitly states that angiotensin receptor blockers (ARBs) like losartan should be withdrawn for 2 weeks before ARR testing if safe and feasible 1. This recommendation is consistent across the most recent guidelines from both the Endocrine Society (2025) and Spanish consensus (2024) 2.

Why 2 Weeks?

ARBs raise renin levels by blocking angiotensin II feedback, which can lead to false-negative results by lowering the aldosterone-to-renin ratio 1. The 2-week washout allows the renin-angiotensin system to return to baseline, improving diagnostic accuracy.

Alternative Antihypertensives During Washout

Recommended medications that minimally interfere with ARR testing:

• Non-dihydropyridine calcium channel blockers: Long-acting verapamil or diltiazem 1, 2
• Alpha-1 blockers: Doxazosin or prazosin 1, 2
• Direct vasodilators: Hydralazine 1, 2

These agents have minimal effects on the renin-angiotensin-aldosterone axis and can maintain blood pressure control during the washout period 2.

Medications to Avoid

• Beta-blockers and alpha-2 agonists (clonidine, methyldopa): These suppress renin and can cause false-positive results by artificially elevating the ARR 1
• Diuretics and mineralocorticoid receptor antagonists: Require 4 weeks washout (longer than ARBs) 1

Important Clinical Considerations

When Washout May Not Be Necessary

If the patient has overt biochemical evidence of primary aldosteronism (plasma renin activity <0.2 ng/mL/h or direct renin concentration <2 mU/L AND aldosterone >15 ng/dL by LC-MS/MS or >20 ng/dL by immunoassay), confirmatory testing may proceed without washout 1.

Safety First

If discontinuing losartan poses significant cardiovascular risk (severe hypertension, recent cardiovascular events), the guidelines acknowledge that screening can be attempted while on ARBs 1. However, interpretation requires understanding that:

• Detectable renin levels on ARBs do NOT exclude primary aldosteronism
• Undetectable renin despite ARB therapy strongly suggests primary aldosteronism 2

Research supports that ARR can be measured on medications in select cases, though with reduced specificity 3, 4.

Correct Hypokalemia First

Before any testing, correct hypokalemia to within normal range using potassium chloride (not potassium bicarbonate formulations), as low potassium suppresses aldosterone secretion and causes false-negative results 1, 2.

Practical Algorithm

1. Assess safety of losartan discontinuation (blood pressure control, cardiovascular stability)
2. If safe to discontinue: Stop losartan and switch to verapamil/diltiazem, doxazosin, or hydralazine
3. Wait 2 weeks for washout
4. Correct any hypokalemia with potassium chloride supplementation
5. Perform ARR testing with proper collection technique (seated, mid-morning, after 2-4 hours upright)
6. If unsafe to discontinue: Proceed with testing on losartan, but interpret results knowing that detectable renin doesn't exclude primary aldosteronism

Common Pitfall

Do not use beta-blockers as the alternative antihypertensive during washout—while they don't cause false-negatives, they suppress renin and increase the rate of false-positive ARR results 1, 5, 6.