Fentanyl

Generic Name: Fentanyl

Brand Names: Duragesic (patch), Actiq, Fentora, Subsys

Fentanyl is an extremely potent synthetic opioid, 50-100x stronger than morphine. Used for severe chronic pain in opioid-tolerant patients only.

Pain ManagementOpioidsControlled Substances

Drug Class

Synthetic Opioid Analgesic (Phenylpiperidine Class)

DEA Schedule

Schedule Schedule II

Pregnancy

Category C — Animal studies have shown adverse fetal effects. No adequate and well-controlled studies in pregnant women. Prolonged use during pregnancy can cause neonatal opioid withdrawal syndrome (NOWS), which may be life-threatening if not recognized and treated. Use only if the potential benefit justifies the potential risk to the fetus.

Available Forms

Transdermal patch (12 mcg/hr, 25 mcg/hr, 50 mcg/hr, 75 mcg/hr, 100 mcg/hr), Transmucosal lozenge (200 mcg, 400 mcg, 600 mcg, 800 mcg, 1200 mcg, 1600 mcg), Buccal tablet (100 mcg, 200 mcg, 400 mcg, 600 mcg, 800 mcg), Sublingual tablet (100 mcg, 200 mcg, 300 mcg, 400 mcg, 600 mcg, 800 mcg), Nasal spray (100 mcg/spray, 400 mcg/spray), IV/IM injection (50 mcg/mL)

What It's Used For

Dosage Quick Reference

These are general dosage guidelines. Your doctor will determine the appropriate dose for your specific situation.

Condition	Starting Dose	Maintenance Dose
Chronic pain (opioid-tolerant patients, transdermal)	25 mcg/hr patch every 72 hours (based on prior opioid dose conversion)	Titrate in 12–25 mcg/hr increments; evaluate after two 72-hour applications
Breakthrough cancer pain (TIRF — transmucosal)	Lowest available unit dose (e.g., 200 mcg lozenge)	Individually titrate over successive episodes; do not exceed 4 units/day once effective dose found
Perioperative analgesia (IV)	50–100 mcg IV (1–2 mcg/kg)	25–50 mcg IV boluses as needed; total dose varies by procedure duration

Side Effects

Common Side Effects:

Nausea and vomiting
Constipation
Sedation
Dizziness
Headache
Application site reactions (transdermal)
Fatigue
Sweating

Serious Side Effects:

Respiratory depression (can be fatal)
Addiction, abuse, and misuse
Overdose death
Serotonin syndrome
Adrenal insufficiency
QT prolongation (high doses)
Severe hypotension
Neonatal opioid withdrawal syndrome

Drug Interactions

Fentanyl interactions can be life-threatening. All providers must be aware of the following.

Benzodiazepines and other CNS depressants (e.g., diazepam, zolpidem, alcohol, gabapentin): Concurrent use causes additive respiratory depression, profound sedation, coma, and death. An FDA Boxed Warning mandates prescribing the lowest doses for the shortest duration if co-use is unavoidable and closely monitoring patients.
CYP3A4 inhibitors (e.g., ritonavir, ketoconazole, clarithromycin, grapefruit juice): Fentanyl is primarily metabolized by CYP3A4. Strong inhibitors increase fentanyl plasma concentrations, which may cause fatal respiratory depression. Reduce fentanyl dose or increase monitoring when adding a CYP3A4 inhibitor.
CYP3A4 inducers (e.g., rifampin, carbamazepine, phenytoin): These accelerate fentanyl metabolism, potentially reducing analgesic efficacy and causing withdrawal symptoms in dependent patients. Dose adjustments may be needed.
Serotonergic agents (e.g., SSRIs, SNRIs, triptans, tramadol, MAOIs): Concurrent use increases the risk of serotonin syndrome — a potentially life-threatening condition characterized by agitation, hyperthermia, tachycardia, clonus, and altered mental status. Monitor closely and discontinue fentanyl if serotonin syndrome is suspected.
Mixed agonist-antagonist opioids (e.g., buprenorphine, nalbuphine, pentazocine): May reduce the analgesic effect of fentanyl or precipitate withdrawal in physically dependent patients. Avoid concurrent use.

Additional Information

Fentanyl is a potent synthetic opioid analgesic used for the management of severe pain, including cancer pain and breakthrough pain in opioid-tolerant patients, as well as for anesthesia. This medication is approximately 100 times more potent than morphine and requires careful dosing and patient selection due to significant risks including fatal respiratory depression.

Mechanism of Action

Fentanyl is a full agonist at mu-opioid receptors, with some activity at kappa and delta receptors. Binding to mu-opioid receptors in the central nervous system produces analgesia, euphoria, respiratory depression, and physical dependence. The drug's high lipophilicity allows rapid penetration of the blood-brain barrier, producing faster onset of action compared to less lipophilic opioids. Fentanyl also binds to opioid receptors in the spinal cord and peripheral tissues, contributing to its analgesic effects. The rapid onset and short duration of IV fentanyl make it ideal for procedural analgesia and anesthesia.

Available Formulations

Fentanyl is available in numerous formulations for different routes and indications: transdermal patches (12, 25, 50, 75, 100 mcg/hour), transmucosal lozenge (oral transmucosal fentanyl citrate), buccal tablet, buccal film, nasal spray, sublingual tablet, sublingual spray, and injection. Each formulation has specific approved indications and is not interchangeable. Transdermal patches are for chronic pain; transmucosal formulations are specifically for breakthrough cancer pain in opioid-tolerant patients.

Medical Uses

Fentanyl injection is used for perioperative analgesia and as a supplement to anesthesia. Transdermal fentanyl is indicated for management of pain in opioid-tolerant patients severe enough to require daily, around-the-clock opioid treatment. Transmucosal fentanyl products (TIRF - Transmucosal Immediate-Release Fentanyl) are indicated only for breakthrough cancer pain in opioid-tolerant cancer patients already receiving and tolerant to around-the-clock opioid therapy.

Dosing Guidelines

Dosing varies significantly by formulation and indication. For transdermal patches, conversion from prior opioid therapy is required; patches are applied every 72 hours. For breakthrough pain products, dosing starts at the lowest available dose regardless of maintenance opioid dose, with careful titration. Injectable fentanyl doses for analgesia range from 25-100 mcg IV; anesthetic doses are much higher. Only patients receiving at least 60 mg oral morphine equivalents daily for at least 1 week are considered opioid-tolerant for fentanyl initiation.

Important Safety Information

Fentanyl carries a boxed warning for life-threatening respiratory depression, particularly during initiation and dose increases; accidental exposure can cause fatal overdose (especially in children); serious risks from concomitant use with benzodiazepines or CNS depressants; neonatal opioid withdrawal syndrome; and addiction, abuse, and misuse potential. TIRF products are available only through a restricted program (TIRF REMS). Transdermal patches can cause fatal overdose if heat is applied or in febrile patients. Naloxone should be available for emergency reversal.

Drug Interactions

Concomitant use with benzodiazepines, other CNS depressants, or alcohol can cause profound sedation, respiratory depression, coma, and death. CYP3A4 inhibitors (ritonavir, ketoconazole, erythromycin, grapefruit juice) increase fentanyl levels and may cause fatal respiratory depression. CYP3A4 inducers may decrease efficacy. Serotonergic drugs may cause serotonin syndrome. MAO inhibitors are contraindicated (or require washout period).

Special Populations

Fentanyl use during pregnancy can cause neonatal opioid withdrawal syndrome; chronic use should be avoided if possible. It is excreted in breast milk; breastfeeding is not recommended. Safety and efficacy of transdermal fentanyl have not been established in pediatric patients under 2 years; TIRF products are not for pediatric use. Elderly patients may be more sensitive and should start at lower doses. Dose reduction is needed in hepatic impairment. Renal impairment may increase sensitivity; use with caution.

Frequently Asked Questions

The transdermal fentanyl patch delivers continuous systemic opioid over 72 hours. Even the lowest-dose patch (12 mcg/hr) can cause fatal respiratory depression in individuals who have not developed tolerance to opioids through prior chronic use. "Opioid-tolerant" is specifically defined as patients receiving at least 60 mg oral morphine equivalents per day (or equivalent) for one week or longer.

Fold the used patch so the adhesive side sticks to itself, then flush it down the toilet. The FDA specifically recommends flushing for fentanyl patches because even used patches retain significant residual drug — enough to cause fatal overdose in children, pets, or opioid-naive adults who might accidentally contact them. Never place used patches in household trash without flushing first.

Yes. External heat sources — heating pads, electric blankets, hot baths, saunas, direct sunlight, and fever — increase skin blood flow and dramatically accelerate fentanyl absorption from the patch. This can result in fatal overdose. Avoid applying heat over or near the patch, and contact your provider if you develop a fever above 102 degrees F (39 degrees C).

Call 911 immediately. Administer naloxone (Narcan) if available — fentanyl overdoses often require multiple doses of naloxone because of fentanyl high potency and receptor binding affinity. Begin rescue breathing or CPR if the person is not breathing. Stay with the person until emergency medical services arrive, as respiratory depression can recur after naloxone wears off.

Fentanyl is approximately 50 to 100 times more potent than morphine and roughly 50 times more potent than heroin on a weight-for-weight basis. This extreme potency is why dosing is measured in micrograms (mcg) rather than milligrams, and why even tiny miscalculations or illicit formulations can be lethal.

Medical Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with your healthcare provider before starting, stopping, or changing any medication. Your doctor can provide personalized recommendations based on your specific health condition and medical history.