Amlodipine Should Not Be Divided Into Multiple Daily Doses
Amlodipine must be administered as a single once-daily dose, not split into divided doses throughout the day. The FDA-approved labeling explicitly states dosing as "once daily" for all indications and patient populations, with no provision for divided dosing 1.
Pharmacokinetic Rationale for Once-Daily Dosing
The pharmacokinetic profile of amlodipine makes divided dosing both unnecessary and inappropriate:
Amlodipine has an exceptionally long elimination half-life of 40-60 hours, which allows for true once-daily dosing with minimal fluctuation in plasma concentrations 2.
Plasma drug concentration fluctuation between doses is only 20-25% with once-daily administration, providing stable blood pressure control throughout the 24-hour period 2.
The drug accumulates to steady-state over 1-1.5 weeks with once-daily dosing, creating consistent therapeutic levels that eliminate any need for dose splitting 2.
Peak plasma concentrations occur 6-8 hours after dosing, but the prolonged half-life ensures continuous antihypertensive effect regardless of when the single daily dose is taken 2.
Clinical Guidelines Support Once-Daily Dosing Only
Multiple authoritative sources confirm single daily dosing:
The Joint National Committee (JNC 7) guidelines explicitly recommend once-daily dosing for amlodipine and state that if inadequate trough control occurs toward the end of the dosing interval, the solution is to increase the total daily dose (not divide it into multiple administrations) 3.
The American Heart Association pediatric pulmonary hypertension guidelines specify once-daily dosing for amlodipine in children, with starting doses of 0.1-0.3 mg/kg/day given as a single daily dose 4.
The 2025 hypertension in pregnancy guidelines list amlodipine with once-daily dosing schedules, with no mention of divided dosing strategies 4.
FDA-Approved Dosing Specifications
The FDA label is unambiguous about dosing frequency:
Adults: 2.5-10 mg once daily for hypertension, with initial doses of 5 mg once daily and maximum doses of 10 mg once daily 1.
Pediatric patients (ages 6-17): 2.5-5 mg once daily, with no provision for divided dosing even in this population 1.
Dose titration should occur every 7-14 days if blood pressure goals are not met, by increasing the once-daily dose rather than splitting it 1.
Clinical Evidence Against Divided Dosing
Research demonstrates that once-daily dosing provides optimal outcomes:
A 1999 randomized study found no advantage to early dose escalation, concluding that dose increases should not be considered until after 6 weeks of treatment at a given once-daily dose 5.
Clinical trials consistently show effective 24-hour blood pressure control with once-daily administration of 5-10 mg, with gradual onset over 4-8 hours and sustained effect throughout the dosing interval 2, 6.
The pharmacodynamic profile shows blood pressure decreases gradually over 4-8 hours after a single dose and remains controlled for the full 24-hour period during chronic once-daily dosing 2.
Common Pitfall to Avoid
Do not confuse amlodipine with short-acting calcium channel blockers (like immediate-release nifedipine) that may require multiple daily doses. Amlodipine's unique long half-life distinguishes it from other dihydropyridines and makes once-daily dosing both appropriate and necessary 2, 6.
If a patient taking 7.5 mg total daily (such as your proposed 5 mg + 2.5 mg split) requires that dose, the correct approach is to prescribe 7.5 mg as a single daily dose, though this would require splitting a 5 mg and 2.5 mg tablet to take together once daily, or using two tablets (5 mg + 2.5 mg) administered simultaneously.