What is a reasonable starting dose of losartan (angiotensin II receptor antagonist) for a patient currently taking 10mg of lisinopril (angiotensin-converting enzyme inhibitor)?

Switching from Lisinopril 10mg to Losartan: Recommended Starting Dose

For a patient on lisinopril 10mg daily, start losartan at 25-50mg once daily. 1

Specific Dosing Guidance

The American College of Cardiology provides clear conversion recommendations when transitioning from ACE inhibitors to ARBs:

• For lisinopril 10-20mg daily → Start losartan 25-50mg once daily 1
• The FDA-approved starting dose for losartan in hypertension is 50mg once daily, with 25mg reserved for patients with possible intravascular depletion (e.g., those on diuretics) 2
• Since your patient is on the lower end of lisinopril dosing (10mg), starting at losartan 25mg daily is the most conservative approach, particularly if the patient has any volume depletion, renal impairment, or is elderly 1, 2

Titration Strategy

After initiating losartan, follow this evidence-based approach:

• Titrate every 1-2 weeks based on blood pressure response, symptoms, and laboratory findings 1
• The target dose for losartan is 50-100mg daily for hypertension and up to 150mg daily for heart failure 3, 1
• Aim to achieve at least 50% of target dose (50mg daily) to ensure clinical benefit 3, 1
• The maximum FDA-approved dose is 100mg daily for hypertension, though guidelines reference up to 150mg for heart failure 1, 2

Critical Safety Monitoring

Check renal function and serum potassium within 1-2 weeks after starting losartan, especially in patients with pre-existing hypotension, diabetes, azotemia, or those taking potassium supplements 1

Common Pitfalls to Avoid

• Do not abruptly discontinue lisinopril before starting losartan—this can lead to clinical deterioration; make the switch directly 1
• Never combine losartan with ACE inhibitors—this combination significantly increases risks of hyperkalemia and renal dysfunction 3, 1
• Avoid concomitant potassium-sparing diuretics or potassium supplements due to hyperkalemia risk 1
• Do not underdose—less than 25% of patients in clinical practice are titrated to target doses, which compromises efficacy 3

Rationale for ARB Switch

Unlike ACE inhibitors, ARBs like losartan do not cause cough, making them the preferred alternative for patients who developed this side effect on lisinopril 1