Section 19 · Monograph
Fentanyl
Reviewed Nov 2026FDA label
Duragesic / genericOpioid agonist (CII)
- Forms
- Patch: 12, 25, 50, 75, 100mcg/h | Inj: 50mcg/mL
- Dose
- Transdermal only in opioid-tolerant patients (at least 60mg oral morphine equivalents/day for 1 week): change every 72h; IV 25-100mcg boluses
- MOA
- Potent μ-opioid receptor agonism
Black Box Warning
- Addiction, abuse and misuse; life-threatening respiratory depression; accidental exposure (especially children); CYP3A4 interactions; risks with benzodiazepines and other CNS depressants; neonatal opioid withdrawal syndrome; exposure to heat can increase absorption of transdermal patches; opioid analgesic REMS
Indications
- Transdermal: management of severe persistent pain requiring daily, around-the-clock, long-term opioid treatment in opioid-tolerant patientsFDA-labeled
- Injection: analgesia and anesthesia adjunctFDA-labeled
Mechanism of Action
- Highly lipophilic, potent full mu-opioid agonist metabolized by CYP3A4 to inactive metabolites
Full Dosing
Adult / usual
- Transdermal: for opioid-tolerant patients only (at least 60mg oral morphine equivalents daily for 1 week); initial patch size from a conversion table; change every 72 hours (some patients every 48 hours); do not cut patches; avoid heat sources
- Allow 24 hours before dose adjustment and 3-6 days to reach steady state when titrating patches
Renal
- IV: 25-100mcg boluses titrated to effect; useful in renal failure because it has no active renal-cleared metabolites
Contraindications
- Patients who are not opioid-tolerant (transdermal)
- Significant respiratory depression; acute or severe asthma in unmonitored settings
- Known or suspected gastrointestinal obstruction; hypersensitivity
Drug Interactions
- Strong CYP3A4 inhibitors (azoles, ritonavir, clarithromycin) can cause fatal respiratory depression; inducers lower levels
- Benzodiazepines and other CNS depressants; serotonergic drugs
Adverse Effects
- Respiratory depression
- Constipation, nausea, sedation
- Application-site reactions
- Chest wall rigidity with rapid IV bolus
Monitoring Parameters
- Sedation and respiratory rate, particularly during titration and when CYP3A4 modulators change
- Fever or external heat exposure (increased absorption)
- Pain control and bowel function
Pregnancy & Lactation
- Neonatal opioid withdrawal syndrome with prolonged use
- Present in milk; monitor infants