What is the proper protocol for switching a patient from lisinopril (Angiotensin-Converting Enzyme (ACE) inhibitor) to losartan (Angiotensin II Receptor Blocker (ARB))?

Protocol for Switching from Lisinopril to Losartan

When switching from lisinopril to losartan, start losartan at 25-50 mg once daily while discontinuing lisinopril, with no overlap period needed between the medications. 1, 2

Rationale and Approach

Switching between an ACE inhibitor (lisinopril) and an ARB (losartan) is commonly done for patients who experience ACE inhibitor-related side effects, particularly cough or angioedema, while still requiring RAAS blockade.

Step-by-Step Protocol:

1. Discontinue lisinopril completely

   • No washout period is required when switching from an ACE inhibitor to an ARB
   • The medications work on different mechanisms in the RAAS pathway

2. Start losartan immediately

   • Initial dose: 25-50 mg once daily 1, 2
   • This is the standard starting dose range per guidelines

3. Monitoring after switch

   • Check blood pressure, renal function, and potassium within 1-2 weeks of initiation 3
   • Pay particular attention to:
     • Blood pressure response
     • Serum creatinine
     • Potassium levels

4. Dose titration

   • Target dose: 50-150 mg once daily 1, 2
   • Mean dose achieved in clinical trials: 129 mg daily 1
   • Consider titrating to at least 50% of target dose (50 mg) for clinical benefit 4

Special Considerations

• Renal impairment: No dosage adjustment needed for various degrees of renal insufficiency 5
• Hepatic impairment: No dosage adjustment needed for mild hepatic impairment 5
• Timing: Losartan can be administered without regard to meals 5
• Pharmacokinetics: Losartan reaches maximum concentration in 1-2 hours and is converted to its active metabolite E3174, which has a half-life of 6-9 hours 5

Common Pitfalls to Avoid

1. Dual RAAS blockade: Never use ACE inhibitors and ARBs simultaneously as this combination increases risk of hyperkalemia, hypotension, and renal dysfunction 6

2. Inadequate monitoring: Failure to check renal function and potassium after switching can miss potential adverse effects

3. Underdosing: Not titrating losartan to an effective dose (at least 50% of target dose) may result in suboptimal outcomes 4

4. Pregnancy: Losartan, like all ARBs, is contraindicated in pregnancy 5

5. Angioedema history: While ARBs may be considered for patients who developed angioedema on ACE inhibitors, some patients may also develop angioedema with ARBs, so caution is advised 3

By following this protocol, you can safely and effectively transition patients from lisinopril to losartan while maintaining effective RAAS blockade and minimizing the risk of adverse effects.