Felodipine Time to Peak Plasma Concentration
Felodipine reaches peak plasma concentration (Tmax) 2.5 to 5 hours after oral administration of the extended-release formulation. 1
Pharmacokinetic Profile by Formulation
The time to peak concentration varies significantly based on the pharmaceutical formulation used:
- Extended-release tablets: Peak plasma concentrations occur at 2.5 to 5 hours after administration, with mean values of approximately 4.4 hours in adults 1, 2
- Conventional (immediate-release) tablets: Peak concentrations occur earlier at approximately 1.3 hours (range 1-3 hours) after administration 2
- Oral solution: Achieves the fastest peak concentration among all formulations 3
The extended-release formulation produces a more gradual absorption profile with lower peak concentrations but higher trough levels compared to immediate-release tablets, making it suitable for once-daily dosing 2
Clinical Implications of Peak Timing
The antihypertensive effect correlates directly with plasma felodipine concentrations without hysteresis, meaning blood pressure reduction occurs in parallel with rising drug levels 3. The EC50 (concentration producing 50% of maximum effect) is approximately 4-6 nmol/L, and most patients achieve therapeutic concentrations that persist throughout the 24-hour dosing interval with extended-release formulations 1
Important Modifying Factors
Several factors can alter the time to peak concentration:
- Food effects: High-fat or high-carbohydrate meals increase Cmax by approximately 60% but do not change the time to peak or overall bioavailability; light meals have no significant effect 1
- Grapefruit juice: Increases bioavailability approximately two-fold (though the specific effect on Tmax is not well-characterized) 1
- Age: Elderly patients show increased peak and trough concentrations with prolonged terminal half-life, but the time to peak remains similar 1, 3
Steady-State Considerations
After repeated dosing with extended-release felodipine, steady-state plasma concentrations are achieved within several days, with peak concentrations approximately 20% higher than after a single dose 1. The terminal elimination half-life ranges from 11-16 hours for immediate-release formulations and extends to approximately 24 hours for extended-release tablets, supporting once-daily administration 4, 5