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Fentanyl (Duragesic Patch)

Opioidprescriptiontransdermal patch · predicted

Potent synthetic μ-opioid agonist delivered transdermally via rate-controlling membrane. Unique pharmacokinetics due to skin depot: slow absorption from reservoir (tmax 24-72h) provides smooth 72-hour analgesia. Terminal half-life of 17 hours reflects continued absorption from skin depot after patch removal; elimination half-life of parent drug is only 2-4 hours. Norfentanyl is inactive primary metabolite. Extensive hepatic metabolism by CYP3A4; strong substrate for drug interactions. WARNING: Serious risk of overdose in opioid-naïve patients; high abuse liability.

Projected serum levels — 50 mcg/hr (≈ 5 mg), custom (shown daily)

Fentanyl (Duragesic Patch)
Fentanyl (Duragesic Patch) modeled serum levels, 50 mcg/hr (≈ 5 mg) custom (shown daily) over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 4 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 4
Fentanyl (Duragesic Patch) modeled serum levels with a loading dose of 119 mcg/hr, then 50 mcg/hr (≈ 5 mg) custom (shown 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: 50 mcg/hr (≈ 5 mg) custom (shown daily) (transdermal patch).

Loading schedule: 119 mcg/hr on day 1, then 50 mcg/hr (≈ 5 mg) custom (shown daily) — reaching therapeutic levels sooner.

Modeled steady state after ~4 days: peak ≈ 1.8 mg, trough ≈ 1.4 mg body load. Population-based estimate over 15 days for a reference dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Opioid
Route modeled
Transdermal patch
Model confidence
predicted
Half-life
17 h
Common dose
50 mcg/hr (≈ 5 mg)
Suggested maximum
100 mcg/hr/day
Reference dose range
12–100 mcg/hr (single dose)
Suggested cadence
custom (shown daily)
Validated against
2.5 mg td — Cmax 0.001 mg/L at 36 h

Documented interactions

  • contraindicated
    Clarithromycin (Biaxin) + Fentanyl (Duragesic Patch) CYP inhibition

    Clarithromycin (Biaxin) mechanism_based of CYP3A4 predicted to change Fentanyl (Duragesic Patch) AUC by ~6.79x

  • contraindicated
    Diltiazem + Fentanyl (Duragesic Patch) CYP inhibition

    Diltiazem mechanism_based of CYP3A4 predicted to change Fentanyl (Duragesic Patch) AUC by ~6.79x

  • contraindicated
    Efavirenz (Sustiva) + Fentanyl (Duragesic Patch) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Fentanyl (Duragesic Patch) AUC by ~0.13x

  • contraindicated
    Grapefruit (whole fruit) + Fentanyl (Duragesic Patch) CYP inhibition

    Grapefruit (whole fruit) mechanism_based of CYP3A4 predicted to change Fentanyl (Duragesic Patch) AUC by ~6.79x

  • contraindicated
    Grapefruit Juice + Fentanyl (Duragesic Patch) CYP inhibition

    Grapefruit Juice mechanism_based of CYP3A4 predicted to change Fentanyl (Duragesic Patch) AUC by ~6.79x

  • contraindicated
    Paxlovid (Nirmatrelvir/Ritonavir) + Fentanyl (Duragesic Patch) CYP inhibition

    Paxlovid (Nirmatrelvir/Ritonavir) mechanism_based of CYP3A4 predicted to change Fentanyl (Duragesic Patch) AUC by ~6.79x

Serum checks 99 modeled interaction pairings for fentanyl (duragesic patch) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Clinical Pharmacokinetics of Transdermal Opioids Grond S et al. · Clinical Pharmacokinetics, 2000 DOI

    Comprehensive review of transdermal opioid pharmacokinetics with focus on fentanyl, describing skin depot kinetics, terminal half-life of 13-25 hours, and clinical implications for dosing.

  2. Clinical pharmacokinetics of transdermal opioids: focus on transdermal fentanyl Müller M et al. · Clinical Pharmacokinetics, 2000 DOI

    Pharmacokinetic analysis showing fentanyl transdermal absorption kinetics result in 20-27 hour terminal half-life due to continued absorption from skin depot following patch removal.

  3. Guidelines for Rational Clinical Use of Fentanyl Transdermal Patch Lennernas H et al. · Drug Design, Development and Therapy, 2015 DOI

    Clinical practice guidelines for transdermal fentanyl covering patch dosing (mcg/hr), titration protocols, food/heat effects, and risk management for potential overdose complications.

  4. CDC Clinical Practice Guideline for Prescribing Opioids for Pain - United States, 2022 Dowell D et al. · MMWR Recommendations and Reports, 2022 DOI

    Updated CDC guideline; transdermal fentanyl is reserved for opioid-tolerant patients only due to its high MME/day equivalence and overdose risk from heat-augmented absorption and inadvertent reservoir exposure.

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