Amlodipine Onset of Action and Starting Dose
Amlodipine does NOT produce measurable blood pressure effects within 30 minutes of oral administration; the onset of action is gradual, occurring over 4-8 hours after a single dose, with peak plasma concentrations reached 6-12 hours post-dose. 1, 2
Pharmacodynamic Profile and Onset
Amlodipine's onset is deliberately slow due to its unique pharmacokinetic properties, including gradual absorption after oral administration and an intermediate rate of drug absorption with peak plasma concentrations occurring 6-8 hours after dosing 1, 2
After single oral doses, blood pressure decreases gradually over 4-8 hours, not within 30 minutes 2
This gradual onset is actually advantageous, as it produces gradual vasodilation that reduces the incidence of reflex tachycardia and headache commonly seen with other calcium antagonists that have rapid onset 3
No change in heart rate occurs after dosing because the gradual onset does not activate physiological reflexes 2
The long elimination half-life of 30-50 hours (some sources report 40-60 hours) means steady-state is not reached until 7-8 days of consecutive daily dosing 1, 2
Standard Starting Doses for Adults
Hypertension
The usual initial antihypertensive dose is 5 mg once daily, with a maximum dose of 10 mg once daily 1
Small, fragile, or elderly patients, or those with hepatic insufficiency should be started on 2.5 mg once daily 1
Dosage adjustments should generally wait 7-14 days between titration steps, though more rapid titration is acceptable if clinically warranted with frequent patient assessment 1
Chronic Stable Angina
The recommended dose is 5-10 mg once daily, with the lower 5 mg dose suggested in elderly patients and those with hepatic insufficiency 1
Most patients will require 10 mg daily for adequate antianginal effect 1, 3
Studies confirm that starting with 5 mg daily and increasing to 10 mg daily if required provides good anti-anginal and anti-ischemic efficacy for a full 24 hours 3
Clinical Pearls and Common Pitfalls
Do not expect immediate blood pressure reduction: Unlike intravenous antihypertensives used in hypertensive emergencies (which have onsets of 1-15 minutes), oral amlodipine is inappropriate for acute blood pressure management 4
Antihypertensive effectiveness is maintained for at least 24 hours with chronic once-daily dosing, making it suitable for convenient once-daily administration at any time of day to improve adherence 1, 5
During chronic dosing, blood pressure decreases from baseline with little fluctuation over the 24-hour interval, and discontinuation results in slow return to baseline over 7-10 days without rebound effect 2
The gradual pharmacodynamic profile means patients won't experience the flushing, headache, and reflex tachycardia that occur with rapid-acting dihydropyridines like immediate-release nifedipine 3, 2