What are the guidelines for switching from lisinopril (Angiotensin-Converting Enzyme (ACE) inhibitor) to losartan (Angiotensin II Receptor Blocker (ARB))?

Guidelines for Switching from Lisinopril to Losartan

When switching from lisinopril (ACE inhibitor) to losartan (ARB), a 36-hour washout period is required between discontinuing lisinopril and starting losartan to prevent the risk of angioedema.

Indications for Switching

The most common reasons for switching from an ACE inhibitor to an ARB include:

1. ACE inhibitor-induced cough:

   • Occurs in 5-10% of white patients and up to 50% in Chinese patients 1
   • Typically non-productive with persistent "tickle" in throat
   • Usually appears within first months of therapy
   • Disappears within 1-2 weeks of discontinuing treatment
   • Recurs within days of rechallenge with another ACE inhibitor

2. Angioedema:

   • Occurs in <1% of patients on ACE inhibitors (more frequent in Black patients) 1
   • Life-threatening reaction requiring permanent avoidance of all ACE inhibitors
   • Caution: Some patients may also develop angioedema with ARBs 1

Switching Protocol

1. Discontinuation of lisinopril:

   • Stop lisinopril and wait at least 36 hours before starting losartan 1
   • This washout period is critical to avoid risk of angioedema

2. Initial dosing of losartan:

   • Start at low dose: 25-50 mg once daily 1
   • Target dose: 50-100 mg once daily 1
   • Mean dose achieved in clinical trials: 129 mg total daily 1

3. Monitoring after switch:

   • Blood pressure
   • Renal function (serum creatinine)
   • Serum potassium (risk of hyperkalemia)
   • Signs of hypotension

Special Considerations

1. Heart Failure Patients:

   • ARBs are alternatives for patients with ACE inhibitor-induced cough or angioedema 1
   • In heart failure with reduced ejection fraction (HFrEF), ARBs have shown benefit in reducing hospitalizations and mortality 1

2. Medication Interactions:

   • Avoid dual blockade of renin-angiotensin system (do not use losartan with ACE inhibitors) 1, 2
   • Monitor potassium levels when used with potassium-sparing diuretics or supplements 1, 2
   • Use caution with NSAIDs (may reduce antihypertensive effect) 2
   • Monitor lithium levels if co-administered 2

3. Dosing Frequency:

   • Once-daily dosing is generally sufficient 1
   • No significant difference in blood pressure control between once-daily and twice-daily dosing 3

Common Pitfalls to Avoid

1. Insufficient washout period: Always maintain the 36-hour gap between stopping lisinopril and starting losartan 1

2. Inadequate dose titration: Start with lower doses and titrate to target doses shown to be effective in clinical trials 1

3. Overlooking monitoring: Regularly monitor renal function and potassium levels, especially in patients with chronic kidney disease 1, 2

4. Assuming complete cross-tolerance: While ARBs have lower risk of cough, some patients who experienced angioedema with ACE inhibitors may also develop it with ARBs 1

5. Dual blockade: Never combine losartan with an ACE inhibitor due to increased risk of hyperkalemia, hypotension, and renal dysfunction 1, 2

By following these guidelines, clinicians can safely and effectively transition patients from lisinopril to losartan when clinically indicated.