What losartan (angiotensin receptor blocker)/hydrochlorothiazide dose is equivalent to lisinopril (angiotensin‑converting enzyme inhibitor) 10 mg/hydrochlorothiazide 12.5 mg for a patient who tolerated the ACE inhibitor but needs an ARB due to cough or angio‑edema?

Equivalent Losartan-Hydrochlorothiazide Dosing for Lisinopril-HCTZ 10-12.5 mg

For a patient switching from lisinopril 10 mg/hydrochlorothiazide 12.5 mg to an ARB-based regimen due to cough or angioedema, start losartan 50 mg/hydrochlorothiazide 12.5 mg once daily, then titrate losartan to 100 mg after 2–4 weeks if blood pressure remains ≥140/90 mmHg.

Rationale for Dose Equivalence

• Lisinopril 10 mg represents a low-to-moderate ACE-inhibitor dose that provides meaningful blood-pressure reduction but is below the maximum approved dose of 40 mg daily. 1

• Losartan 50 mg once daily is the recommended starting dose for hypertension and provides comparable blood-pressure lowering to low-dose ACE inhibitors when combined with hydrochlorothiazide 12.5 mg. 2, 3

• The hydrochlorothiazide component remains unchanged at 12.5 mg because this dose provides near-maximal diuretic effect with minimal metabolic side effects, and both lisinopril-HCTZ and losartan-HCTZ combinations use this same thiazide dose in their initial formulations. 2, 3, 4

• Clinical trials demonstrate that losartan 50 mg/HCTZ 12.5 mg produces additive blood-pressure reductions of approximately 17.2/13.2 mmHg (systolic/diastolic), with 78% of patients achieving adequate control, making it an appropriate initial equivalent. 3

Titration Strategy

• If blood pressure remains ≥140/90 mmHg after 2–4 weeks on losartan 50 mg/HCTZ 12.5 mg, increase losartan to 100 mg while maintaining HCTZ at 12.5 mg, as this represents the maximum recommended losartan dose for hypertension. 2

• The target dose of losartan is 100 mg once daily for optimal cardiovascular outcomes in hypertension, though 50 mg may suffice in patients who were well-controlled on low-dose lisinopril. 2

• Re-measure blood pressure 2–4 weeks after any dose adjustment, aiming to achieve a target of <130/80 mmHg (minimum <140/90 mmHg) within 3 months of the switch. 1

Monitoring After the Switch

• Check serum creatinine/eGFR and potassium within 1–2 weeks of switching from lisinopril to losartan, especially in patients with chronic kidney disease, diabetes, or baseline renal impairment. 2

• A modest creatinine rise of 0.1–0.3 mg/dL is expected and reflects hemodynamic changes rather than true renal injury; discontinuation is not required unless acute tubular necrosis is evident. 2

• Monitor for symptomatic hypotension during the first 1–2 weeks, particularly in elderly patients or those with volume depletion. 2

Special Considerations for ACE-Inhibitor Intolerance

• Angioedema history: Although ARBs have a lower incidence of angioedema than ACE inhibitors, patients with prior ACE-inhibitor-induced angioedema may still develop this reaction with losartan; extreme caution and close monitoring are required. 1, 2

• Cough: Losartan does not inhibit kininase and is associated with a much lower incidence of cough compared with ACE inhibitors, making it the preferred alternative when cough limits ACE-inhibitor use. 1

• Direct transition: Switch directly from lisinopril to losartan without a washout period; start losartan 50 mg/HCTZ 12.5 mg on the day after the last lisinopril dose, as no pharmacologic washout is required when moving between these drug classes. 2

Why Not Higher Initial Losartan Doses?

• Starting with losartan 100 mg/HCTZ 12.5 mg immediately would be appropriate only if the patient had been on a higher lisinopril dose (e.g., 20–40 mg) or had documented resistant hypertension requiring maximal RAS blockade from the outset. 2

• The 50 mg starting dose allows assessment of tolerability and avoids excessive blood-pressure lowering in patients who may have been adequately controlled on the lower lisinopril dose. 2, 3

Common Pitfalls to Avoid

• Do not combine losartan with lisinopril (dual RAS blockade), as this increases the risk of hyperkalemia, syncope, and acute kidney injury by 2–3-fold without added cardiovascular benefit. 1, 2

• Do not delay the switch if the patient has developed cough or angioedema on lisinopril; these adverse effects mandate immediate discontinuation and substitution with an ARB. 1

• Do not assume treatment failure without first confirming medication adherence and excluding white-coat hypertension with home blood-pressure monitoring (target <135/85 mmHg). 1

• Do not increase HCTZ above 12.5 mg as the primary strategy for uncontrolled blood pressure; instead, titrate losartan to 100 mg or add a third agent (calcium-channel blocker) if needed. 1, 2