Fentanyl
DURAGESIC
Pronunciation: FEN-ta-nil (dur-a-JEE-zik)
“Fountain eel’s Durable analgesic”
pinpoint pupils → opioid
Used patches are to be flushed down the toilet
What it isHigh-potency lipophilic mu agonist; severe pain, anesthesia and transdermal chronic pain.
Why this oneNo active metabolites; lipophilicity enables patch and transmucosal delivery when oral dosing is impractical.
What limits itPatch takes 12 to 24 hours to work and is only for opioid-tolerant patients; heat raises absorption. Potency makes dosing errors lethal.
Pearls
- Patch: halve starting dose in mild-moderate renal impairment; avoid if severe.
- Accidental patch exposure kills children; fold used patches sticky sides together.
- Transmucosal forms: breakthrough cancer pain in opioid-tolerant patients only.
Fentanyl prescription history
Animated chart of estimated U.S. prescriptions per year, Opioid analgesics (1900–2026). Fentanyl enters in 1991 (estimated).
FDA-approved for
- pain (1968)
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilityRespiratory depression, dependence and overdose; risk rises sharply with sedatives or impaired clearance.
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Severe, persistent pain requiring an opioid, inadequately treated by alternatives — opioid-tolerant patients only | Adults (opioid-tolerant) | By conversion table (e.g., oral morphine 60–134 mg/day → 25 mcg/h), one patch q72h | Individually titrated; one patch q72h (q48h only if 72-h regimen fails after dose increase) | Undefined (>100 mcg/h: use multiple systems) |
| Severe, persistent pain — opioid-tolerant | Peds ≥2 y (opioid-tolerant) | By oral-morphine conversion table, one patch q72h | Individually titrated; q72h only | Undefined |
Titration First increase no sooner than 3 days after initial application; thereafter wait at least two 3-day applications before each further increase.
Renal Mild–moderate: start at one-half the usual dose, titrate slowly, monitor for respiratory/CNS depression; severe: avoid.
Hepatic Mild–moderate: start at one-half the usual dose, titrate slowly, monitor for respiratory/CNS depression; severe: avoid.
Conversion tables are conservative and must not be used to convert from fentanyl patch to other opioids. Dose increments: 12 mcg/h per 45 mg/24 h supplemental oral morphine. Intermediate 37.5 and 62.5 mcg/h strengths available.
Instructions
- Opioid-tolerant only; discontinue or taper other extended-release opioids when starting. Never first opioid.
- Apply to intact, non-irritated, non-irradiated flat skin (chest, back, flank, upper arm; upper back in young children); clip hair, clean with water only.
- Do not cut or alter; press firmly with palm for 30 seconds; wear 72 h, then apply new patch to a different site.
- Avoid external heat (heating pads, electric blankets, saunas, hot tubs, sunbathing) over the patch.
- Wash hands after application; dispose by folding adhesive sides together and flushing.
- Do not stop abruptly; taper by ≤25% of total daily dose every 2–4 weeks.
Available strengths
- patch 12, 25, 37.5, 50, 62.5, 75, 87.5, 100 mcg/hr
Contraindications
- Opioid non-tolerant patients
- Acute or intermittent pain, or short-term opioid need
- Postoperative pain (incl. outpatient/day surgery, e.g., tonsillectomy)
- Mild pain
- Significant respiratory depression
- Acute or severe bronchial asthma in an unmonitored setting or without resuscitative equipment
- Known or suspected GI obstruction, including paralytic ileus
Cautions
- Addiction, abuse, and misuse
- Life-threatening respiratory depression
- Accidental exposure
- Benzodiazepines/other CNS depressants
- Neonatal opioid withdrawal syndrome
- Opioid analgesic REMS
- CYP3A4 inhibitors and inducers
- External heat increases absorption
- Fever/elevated body temperature increases absorption
- Opioid-induced hyperalgesia and allodynia
- Serotonin syndrome with serotonergic drugs
- Respiratory depression in chronic lung disease, elderly, cachectic, debilitated
- Adrenal insufficiency
- Severe hypotension
- Increased ICP, brain tumors, head injury, impaired consciousness
- Cardiac disease (bradycardia)
- Hepatic impairment
- Renal impairment
- GI complications
- Seizures in seizure disorders
- Withdrawal (no abrupt discontinuation)
- Impaired driving/machinery operation
Adverse reactions
- Nausea
- Vomiting
- Somnolence
- Dizziness
- Insomnia
- Constipation
- Hyperhidrosis
- Fatigue
- Feeling cold
- Anorexia
- Headache
- Diarrhea
Pregnancy Prolonged use may cause neonatal opioid withdrawal syndrome; human data insufficient for birth-defect risk; embryocidal in rats without malformations.
Lactation Fentanyl is excreted in human milk; breastfeeding not recommended (infant sedation/respiratory depression).
Cost
| Strength | #/mo | generic $/unit | CostPlus | |
|---|---|---|---|---|
| 12 mcg/hr | patch | per unit | $8.99/ea | not offered |
| 25 mcg/hr | patch | per unit | $6.01/ea | not offered |
| 37.5 mcg/hr | patch | per unit | $35.03/ea | not offered |
| 50 mcg/hr | patch | per unit | $9.07/ea | not offered |
| 62.5 mcg/hr | patch | per unit | $57.69/ea | not offered |
| 75 mcg/hr | patch | per unit | $15.87/ea | not offered |
| 87.5 mcg/hr | patch | per unit | not offered | |
| 100 mcg/hr | patch | per unit | $18.36/ea | not offered |
Generic entry1990
Serotonicity
This drug is routinely called serotonergic. By Gillman’s human-effect criteria it does not raise serotonin in the synapse.
Opioid effects and respiratory/CNS-depressant interactions remain important, but this drug is not a clinically significant SRI by the Gillman framework.
Gillman’s four human testsA measurable SERT affinity that fails all four is not clinical serotonicity.
- Retarded orgasm
- Efficacy in OCD and cataplexy
- Clonus and hyperreflexia in single-drug overdose
- Serotonin toxicity when combined with an MAOI
Non-elevating actionNone recorded
Evidence confidenceHigh
Background: what serotonicity is · what is and is not an SRI · what counts as a relevant MAOI.
Open Fentanyl in the interactive console ↗
Memory aids: interaction avatars
Open Fentanyl in the interactive console ↗
Self-check
- How long can fentanyl patches take to start working?
12–24 hours. - What can heat do to fentanyl patch absorption?
Increase it.