There is No Direct Dose Equivalence Between Losartan and Amlodipine
Losartan (an angiotensin II receptor blocker) and amlodipine (a calcium channel blocker) are fundamentally different drug classes with distinct mechanisms of action, and therefore cannot be converted using a dose equivalence formula. These medications work through entirely separate pathways—losartan blocks the renin-angiotensin system while amlodipine blocks calcium channels in vascular smooth muscle 1, 2.
Why This Question Reflects a Misunderstanding
Different mechanisms mean different effects: Losartan 50 mg does not have an "equivalent" amlodipine dose because they achieve blood pressure reduction through completely different physiological mechanisms 1, 2.
The clinical trials directly comparing these agents show they are not interchangeable: Studies comparing losartan 50 mg to amlodipine 5 mg or 10 mg demonstrate different efficacy profiles, with amlodipine generally producing greater blood pressure reductions (mean difference of 2.3/2.3 mm Hg systolic/diastolic) 1.
If You Need to Switch Medications
If switching from losartan to amlodipine is clinically necessary, start amlodipine at its standard initial dose of 5 mg once daily, regardless of the losartan dose, and titrate based on blood pressure response 1, 2.
Practical Switching Approach:
Start amlodipine at 5 mg once daily as the standard initial dose for hypertension 1, 3.
Titrate to amlodipine 10 mg once daily after 2-4 weeks if blood pressure remains above goal 1, 3.
Monitor for ankle edema, which occurs significantly more frequently with amlodipine (15% vs 4% with losartan) and is a common reason for discontinuation 4.
Important Clinical Context
Losartan 50 mg once daily is actually a suboptimal dose for most indications. The evidence strongly supports higher dosing:
For heart failure with reduced ejection fraction, the target dose is 150 mg daily, as demonstrated in the HEAAL trial showing 10% relative risk reduction in death or heart failure hospitalization compared to 50 mg daily 5, 6.
For hypertension, the maximum recommended dose is 100 mg once daily 6.
The ELITE II trial showed losartan 50 mg daily was inferior to ACE inhibitor therapy, highlighting that this dose may be inadequate 5.
Common Pitfall to Avoid
Do not assume that because a patient is on "one pill" of losartan, they need "one pill" of amlodipine. The dosing, efficacy, and tolerability profiles are completely different between these drug classes. Base your choice on the patient's blood pressure response, comorbidities (heart failure, diabetes, chronic kidney disease), and tolerance of side effects rather than attempting a dose conversion 1, 2, 7.