Olmesartan Dose Equivalent to Irbesartan 300mg
Switch from irbesartan 300mg to olmesartan 40mg once daily, as this represents the maximum recommended dose of olmesartan and provides equivalent or superior blood pressure control. 1
Dose Equivalence Rationale
The standard dose ranges establish the conversion framework:
- Irbesartan: 150-300mg once daily (with 300mg being the maximum dose) 1
- Olmesartan: 20-40mg once daily (with 40mg being the maximum dose) 1
When a patient is on irbesartan 300mg (the maximum therapeutic dose), the equivalent is olmesartan 40mg once daily, which represents the maximum dose in the olmesartan range 1.
Supporting Evidence for Equivalence
Head-to-head comparative trials demonstrate that olmesartan 20mg provides superior blood pressure reduction compared to irbesartan 150mg, suggesting that olmesartan is approximately twice as potent on a milligram-per-milligram basis 2. This supports the 300mg irbesartan to 40mg olmesartan conversion.
In the EARTH study comparing these agents directly, irbesartan and olmesartan showed comparable blood pressure reduction ability with equivalent safety profiles, though olmesartan at its recommended doses showed greater variance in blood pressure control 3.
Clinical reviews confirm that olmesartan 10-40mg provides antihypertensive efficacy superior to irbesartan 150mg in head-to-head trials, with faster onset of action and greater reductions in both systolic and diastolic blood pressure 4.
Practical Switching Algorithm
When converting from irbesartan 300mg:
- Start olmesartan 40mg once daily (the maximum recommended dose) 1
- Monitor blood pressure within 2-4 weeks after switching to assess individual response 5
- Both medications can be taken without regard to meals 1
- Maintain the same once-daily dosing schedule 1
Important Safety Considerations
Both medications share identical contraindications and monitoring requirements:
- Avoid in pregnancy (both are teratogenic) 1
- Do not combine with ACE inhibitors or direct renin inhibitors 1
- Monitor for hyperkalemia, especially in patients with chronic kidney disease or those on potassium supplements 1
- Monitor renal function, particularly in patients with bilateral renal artery stenosis 1
The risk of angioedema exists with both agents, though it is lower than with ACE inhibitors 1. If a patient had angioedema with an ACE inhibitor, wait 6 weeks before initiating either ARB 1.
Clinical Advantages of Each Agent
Irbesartan 300mg has proven renoprotective effects in diabetic nephropathy, demonstrated in the IDNT and IRMA-2 trials, with benefits independent of blood pressure reduction 6. If the patient is on irbesartan specifically for diabetic nephropathy, reconsider whether switching is necessary, as irbesartan has the strongest evidence base for this indication 6.
Olmesartan provides consistent 24-hour blood pressure control with potentially greater antihypertensive efficacy than other ARBs at recommended doses 4. However, it lacks the extensive renal outcome data that irbesartan possesses 6, 4.