How Quickly Does Amlodipine Work
Amlodipine begins to work within 1-2 hours after oral administration, but its full antihypertensive effect develops gradually over 4-8 hours, with peak plasma concentrations occurring between 6-12 hours after dosing. 1, 2
Onset of Action
- Amlodipine has a gradual onset of action due to its intermediate rate of absorption and unique drug-receptor interaction characteristics 2
- After oral administration, peak plasma concentrations are reached between 6-12 hours 1
- Blood pressure begins to decrease gradually over 4-8 hours following a single dose 2
- The gradual onset helps prevent reflex tachycardia that can occur with faster-acting calcium channel blockers 2
Pharmacokinetic Properties Contributing to Onset
- Amlodipine has high oral bioavailability (60-80%) 2, 3
- The drug has a slow elimination rate with a long terminal half-life of 30-50 hours 1, 3
- It is extensively metabolized in the liver but does not undergo significant first-pass metabolism 3
- The volume of distribution is large (21 L/kg) with high protein binding (98%) 3
Full Effect Timeline
- While initial effects begin within hours, the full therapeutic effect develops over 7-10 days of consecutive daily dosing as the drug reaches steady-state plasma levels 1, 2
- The long half-life (35-50 hours) allows for once-daily dosing with minimal fluctuation (20-25%) in plasma concentration between doses 2, 4
- This provides sustained 24-hour blood pressure control even if a dose is occasionally missed 4
Clinical Considerations
- In hypertension management, amlodipine is considered a first-line calcium channel blocker due to its long duration of action 5
- The gradual onset minimizes side effects that can occur with rapid-acting antihypertensives 6
- Blood pressure reduction is dose-dependent, with higher doses producing greater reductions 6
- Standing diastolic blood pressure reductions of approximately 1.1,4.8, and 8 mmHg have been observed six hours after 2.5, and 10 mg doses, respectively 6
Comparison to Other Calcium Channel Blockers
- Amlodipine has a longer duration of action compared to other dihydropyridine calcium channel blockers like felodipine 7
- In comparative studies, amlodipine provided more effective nighttime blood pressure control than felodipine, likely due to its longer half-life 7
- Unlike immediate-release nifedipine, amlodipine's gradual onset avoids dangerous rapid blood pressure drops 5
Important Considerations
- Elderly patients and those with hepatic insufficiency have decreased clearance of amlodipine with a resulting increase in drug exposure by approximately 40-60%, which may require lower initial doses 1
- Common side effects include edema, palpitations, dizziness, and flushing, which are more common with the higher dose of 10 mg 4
- Unlike some calcium channel blockers, amlodipine does not significantly alter heart rate or sinoatrial nodal function 1