Equivalent Dosing of Losartan to Telmisartan
When switching from telmisartan 80 mg to losartan, start with losartan 100 mg daily to achieve a comparable antihypertensive effect. 1
Comparative Efficacy and Dosing
Telmisartan and losartan are both angiotensin II receptor blockers (ARBs) but have different potency and pharmacokinetic profiles:
- Telmisartan has a longer half-life and provides more sustained 24-hour blood pressure control compared to losartan
- Studies have shown that telmisartan is more potent than losartan at equivalent doses:
- Telmisartan 40 mg produces greater blood pressure reductions than losartan 50 mg
- Telmisartan 80 mg produces greater blood pressure reductions than losartan 100 mg 2
Evidence from Clinical Studies
A randomized, double-blind study comparing telmisartan and losartan found:
- Telmisartan 40 mg reduced blood pressure significantly more than losartan 50 mg (DBP response rates: 46.3% vs. 32.5%, p=0.010)
- Telmisartan 80 mg reduced blood pressure significantly more than losartan 100 mg (DBP response rates: 79.3% vs. 65.3%, p=0.008) 2
Another study demonstrated that telmisartan 80 mg provided superior blood pressure control during the last 6 hours of the 24-hour dosing interval compared to losartan 50 mg plus hydrochlorothiazide 12.5 mg, which is particularly important for controlling early morning blood pressure surges 3.
Practical Dosing Conversion
Based on the most recent clinical guidelines:
- When converting from telmisartan 80 mg to losartan, use losartan 100 mg daily 1
- For telmisartan 40 mg, the equivalent losartan dose would be approximately 50-100 mg
- For lower doses of telmisartan, start with losartan 50 mg and titrate as needed
Important Monitoring Considerations
When switching between these medications:
- Monitor blood pressure closely, especially during the first 1-2 weeks after switching
- Pay particular attention to morning blood pressure readings, as losartan may not provide the same 24-hour coverage as telmisartan 4
- Consider twice-daily dosing of losartan if once-daily dosing does not provide adequate 24-hour control
Potential Pitfalls
- The M/E ratio (morning effect versus evening effect) for losartan (0.49/0.16) is significantly lower than for telmisartan (0.88/0.88), indicating that losartan may not provide consistent 24-hour coverage 4
- Losartan 25 mg (a common starting dose) has been shown to be insufficient for adequate antihypertensive effect and duration of action compared to other ARBs 4
- When switching from telmisartan to losartan, patients may experience less effective blood pressure control, particularly in the early morning hours when cardiovascular risk is highest
Remember that the goal of therapy is to maintain adequate blood pressure control throughout the entire 24-hour period to reduce cardiovascular morbidity and mortality.