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Felodipine (Plendil)

Calcium Channel Blockerprescriptionoral · inferred

Dihydropyridine calcium channel blocker for hypertension and angina. Undergoes extensive first-pass hepatic metabolism via CYP3A4, resulting in low oral bioavailability. Highly susceptible to grapefruit-drug interactions. Available as extended-release tablets for once-daily dosing.

Projected serum levels — 5 mg, once daily

Felodipine (Plendil)
Felodipine (Plendil) modeled serum levels, 5 mg once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 3 days. 0 0.50 1 1.5 2 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 3
Felodipine (Plendil) modeled serum levels with a loading dose of 10.3 mg, then 5 mg once daily The first dose is larger so levels approach steady state faster. 0 0.50 1 1.5 2 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 5 mg once daily (oral).

Loading schedule: 10.3 mg on day 1, then 5 mg once daily — reaching therapeutic levels sooner.

Modeled steady state after ~3 days: peak ≈ 1.4 mg, trough ≈ 0.78 mg body load. Population-based estimate over 15 days for a 5 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Calcium Channel Blocker
Route modeled
Oral
Model confidence
inferred
Half-life
25 h
Common dose
5 mg
Suggested maximum
10 mg/day
Reference dose range
2.5–10 mg (single dose)
Suggested cadence
once daily
Validated against
10 mg oral — Cmax 0.014 mg/L at 3.5 h

Documented interactions

  • contraindicated
    Carbamazepine (Tegretol) + Felodipine (Plendil) CYP induction

    Carbamazepine (Tegretol) inducer of CYP3A4 predicted to change Felodipine (Plendil) AUC by ~0.20x

  • contraindicated
    Clarithromycin (Biaxin) + Felodipine (Plendil) CYP inhibition

    Clarithromycin (Biaxin) mechanism_based of CYP3A4 predicted to change Felodipine (Plendil) AUC by ~10.00x

  • contraindicated
    Dasatinib (Sprycel) + Felodipine (Plendil) CYP inhibition

    Dasatinib (Sprycel) time_dependent_inhibitor of CYP3A4 predicted to change Felodipine (Plendil) AUC by ~5.00x

  • contraindicated
    Diltiazem + Felodipine (Plendil) CYP inhibition

    Diltiazem mechanism_based of CYP3A4 predicted to change Felodipine (Plendil) AUC by ~10.00x

  • contraindicated
    Efavirenz (Sustiva) + Felodipine (Plendil) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Felodipine (Plendil) AUC by ~0.12x

  • contraindicated
    Grapefruit (whole fruit) + Felodipine (Plendil) CYP inhibition

    Grapefruit (whole fruit) mechanism_based of CYP3A4 predicted to change Felodipine (Plendil) AUC by ~10.00x

Serum checks 222 modeled interaction pairings for felodipine (plendil) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Interaction of citrus juices with felodipine and nifedipine Bailey DG et al. · Lancet, 1991 DOI

    Landmark study demonstrating that grapefruit juice increases felodipine bioavailability 2.8-fold, establishing the original grapefruit-drug interaction (mean 284% of control, range 164-469%).

  2. Grapefruit juice increases felodipine oral availability in humans by decreasing intestinal CYP3A protein expression Dresser GK et al. · Journal of Clinical Investigation, 2000 DOI

    Mechanistic study showing grapefruit-mediated 62% reduction in intestinal CYP3A4 protein, explaining the dramatic increase in felodipine systemic exposure.

  3. Pharmacokinetic analysis of felodipine-grapefruit juice interaction based on an irreversible enzyme inhibition model Takanaga H et al. · Journal of Pharmacokinetics and Biopharmaceutics, 2000 DOI

    Quantitative PK modeling of grapefruit-felodipine interaction demonstrating mechanism-based intestinal CYP3A4 inhibition by furanocoumarins.

3 published studies referenced in the app, each with a plain-language summary.