How long until the effect of amlodipine (calcium channel blocker) 2.5mg is noticeable?

Onset of Amlodipine 2.5mg Effect

Amlodipine 2.5mg begins lowering blood pressure within 4-8 hours after the first dose, but the full antihypertensive effect develops gradually over 1-2 weeks of daily dosing. 1, 2

Initial Blood Pressure Response

• After a single 2.5mg dose, blood pressure decreases gradually over 4-8 hours, with peak plasma concentrations occurring 6-12 hours after administration 1, 2
• The gradual onset is due to amlodipine's intermediate absorption rate and its unique physicochemical interaction with cell membrane receptors 2
• No significant change in heart rate occurs during this initial period because the gradual onset does not activate physiological reflex responses 2

Time to Steady-State and Maximum Effect

• Steady-state plasma levels are reached after 7-8 days of consecutive daily dosing, which is when the full therapeutic effect becomes apparent 1
• The drug accumulates over 1-1.5 weeks due to its exceptionally long elimination half-life of 30-50 hours 1, 2
• In clinical trials, amlodipine 2.5mg achieved target blood pressure reduction in 80% of hypertensive patients with renal dysfunction after 8 weeks of treatment 3

Practical Clinical Implications

• Blood pressure monitoring should occur at 24 hours post-dose during chronic therapy, as amlodipine maintains antihypertensive effectiveness throughout the entire 24-hour dosing interval with minimal peak-to-trough fluctuation (20-25%) 1, 2
• If a dose is missed, blood pressure control is maintained due to the long half-life, providing continuous protection during incidental non-compliance 4
• Dose titration should not occur before 4 weeks of treatment at a given dose, as this allows adequate time to assess the full therapeutic response 5

Important Caveats

• The 2.5mg dose represents the minimum effective dose for blood pressure reduction, with dose-related efficacy demonstrated in controlled trials 5
• Elderly patients and those with hepatic insufficiency may experience 40-60% higher drug exposure, potentially leading to faster or more pronounced effects even at the 2.5mg dose 1
• Discontinuation results in a slow return to baseline blood pressure over 7-10 days without rebound hypertension, reflecting the drug's prolonged elimination 2