From the Guidelines
The equivalent dose of irbesartan to losartan 100 mg is 300 mg, as indicated in the 2020 ACC/AHA clinical performance and quality measures for adults with heart failure 1. When switching a patient from losartan 100 mg to irbesartan, prescribe irbesartan 300 mg once daily. Both medications are angiotensin II receptor blockers (ARBs) used to treat hypertension and other cardiovascular conditions, but they have different potencies.
- Key differences between irbesartan and losartan include:
- Half-life: Irbesartan has a longer half-life (11-15 hours) than losartan (2 hours, though its active metabolite lasts 6-9 hours), allowing for consistent 24-hour blood pressure control.
- Bioavailability: Irbesartan has higher bioavailability (60-80%) compared to losartan (33%).
- Metabolic activation: Irbesartan doesn't require metabolic activation to achieve its full therapeutic effect. When making this medication switch, monitor blood pressure closely for the first few weeks to ensure adequate control, and be aware that the full antihypertensive effect may take 2-4 weeks to develop.
- Additional considerations:
- No dosage adjustments are typically needed when switching between these medications at their equivalent doses.
- The target dose of losartan is 100 mg, as recommended by the ACC/AHA guidelines, although the maximal dose approved by the FDA is also 100 mg 1.
- The dose of irbesartan equivalent to losartan 100 mg is supported by the 2020 ACC/AHA clinical performance and quality measures for adults with heart failure, which lists the target dose of irbesartan as 300 mg once daily 1.
From the Research
Irbesartan Dose Equivalent to Losartan 100 mg
- The equivalent dose of irbesartan to losartan 100 mg is not directly stated in the provided studies, but we can look at the dosing comparisons made in the studies.
- In the study 2, irbesartan 150 mg and losartan 50 mg were compared, and at week 4, the dose was doubled to irbesartan 300 mg or losartan 100 mg if the seated diastolic blood pressure was ≥ 90 mm Hg.
- This suggests that irbesartan 300 mg is the dose being compared to losartan 100 mg in this study.
- Another study 3 compared the angiotensin II receptor blockade of different doses of valsartan with losartan, irbesartan, and candesartan, but did not directly compare irbesartan and losartan doses.
- However, the study 4 mentions that irbesartan provides a greater and longer-lasting antihypertensive effect than losartan, but does not provide a direct dose comparison.
- Based on the available information, it appears that irbesartan 300 mg may be considered equivalent to losartan 100 mg, but this is not explicitly stated in the studies 2, 4, 3.