FENTANYL-25
Clinical safety rating: avoid
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur.
Mu-opioid receptor agonist; produces analgesia by activating G-protein coupled opioid receptors in the CNS, leading to decreased neurotransmitter release and hyperpolarization of neurons.
| Metabolism | Primarily hepatic via CYP3A4; major metabolites include norfentanyl (inactive); minor pathways: CYP3A5, CYP3A7. |
| Excretion | Renal (75% as metabolites, <10% unchanged); Fecal (9%); Biliary (minor). |
| Half-life | Terminal elimination half-life: 2-4 hours in healthy adults; prolonged to 3-12 hours in elderly, hepatic impairment, or critical illness; context: duration of action shorter due to redistribution. |
| Protein binding | 80-85% primarily to alpha-1-acid glycoprotein and albumin. |
| Volume of Distribution | 3-5 L/kg; high Vd indicates extensive tissue distribution, including redistribution to fat and muscle. |
| Bioavailability | Transdermal: 90-100% (but variable); IM: 100%; Oral: <30% (first-pass); Sublingual/Buccal: 50-90%; Intranasal: 70-80%. |
| Onset of Action | IV: 30-60 seconds; IM: 7-15 minutes; Transdermal: 12-24 hours (steady state at 72 hours); Intrathecal/Epidural: 5-10 minutes. |
| Duration of Action | IV: 30-60 minutes (analgesic); IM: 1-2 hours; Transdermal: 72 hours (patch); context: dose-dependent, respiratory depression may outlast analgesia. |
| Molecular Weight | 336.47 |
25 mcg/h transdermal patch applied every 72 hours; for opioid-tolerant patients only.
| Dosage form | FILM, EXTENDED RELEASE |
| Renal impairment | GFR < 30 mL/min: consider dose reduction by 50% and monitor for respiratory depression; avoid in severe renal impairment (GFR < 15 mL/min) if possible. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: avoid use or reduce dose by 75% with close monitoring. |
| Pediatric use | Not recommended for pediatric use; safety and efficacy not established. |
| Geriatric use | Initiate with lowest available dose (12.5 mcg/h) and titrate slowly; monitor for respiratory depression and delirium; reduce dose by 25-50% in patients over 65 years. |
| 1st trimester | Avoid use due to risk of congenital malformations; limited data but association with neural tube defects suggested. |
| 2nd trimester | Use only if clearly needed; may cause fetal dependence and withdrawal; risk of preterm labor with chronic use. |
| 3rd trimester | Avoid prolonged use; high risk of neonatal respiratory depression and opioid withdrawal syndrome. |
Clinical note
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur.
| FDA category | Positive |
| Placental transfer | Rapidly crosses placenta; fetal concentrations approximate maternal levels after IV administration. |
| Breastfeeding |
■ FDA Black Box Warning
Risk of respiratory depression, especially in non-opioid tolerant patients; risk of addiction, abuse, and misuse; risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy; risk of fatal overdose with accidental ingestion; risk of interaction with alcohol and CNS depressants.
| Common Effects | Constipation |
| Serious Effects |
Hypersensitivity to fentanyl or any componentAcute or severe bronchial asthmaUpper airway obstructionConcurrent use or within 14 days of MAO inhibitors
| Precautions | Respiratory depression; hypotension, bradycardia; serotonin syndrome with serotonergic drugs; adrenal insufficiency; severe hypotension; seizures; opioid-induced hyperalgesia; tolerance and physical dependence; withdrawal with abrupt discontinuation; elderly and cachectic patients; renal impairment. |
| Food/Dietary |
Loading safety data…
| Enters breast milk in low concentrations; monitor for drowsiness and feeding difficulties in infant; AAP recommends caution with repeated use. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Limited human data; animal studies show no teratogenicity at clinically relevant doses. Second/third trimester: Chronic use may cause fetal opioid dependence and neonatal abstinence syndrome (NAS). No structural malformations reported. Risk of premature delivery, poor fetal growth. Use only if benefits outweigh risks. |
| Fetal Monitoring | Monitor maternal vital signs (respiratory rate, oxygen saturation, sedation level). Fetal heart rate monitoring during labor. Watch for signs of opioid toxicity in neonate after birth. Consider umbilical cord blood drug levels if indicators of exposure. |
| Fertility Effects | In animal studies, no effects on fertility. In humans, no adequate studies. However, opioid-induced hypogonadism may occur with chronic use, potentially impairing fertility. Withdrawal may normalize function. |
| No known food interactions. Avoid alcohol consumption as it may potentiate central nervous system depression and increase risk of respiratory depression. |
| Clinical Pearls | Fentanyl-25 mcg/h patch provides systemic opioid analgesia for 72 hours. Apply to non-irritated, non-hairy skin on chest, back, flank, or upper arm. Avoid heat sources (heating pads, saunas) which increase absorption and risk of overdose. Do not cut or damage the patch. Monitor for respiratory depression, especially in opioid-naïve patients. Initiate at lowest dose and titrate based on response. Dispose of used patches by folding adhesive sides together and flushing down toilet or returning to take-back program. |
| Patient Advice | Apply the patch to clean, dry, hairless skin on your chest, back, flank, or upper arm. Avoid areas with cuts or rashes. · Replace the patch every 72 hours (3 days). Remove the old patch before applying a new one to a different skin site. · Do not use heating pads, electric blankets, hot water bottles, or saunas while wearing the patch as increased heat speeds up drug absorption. · Do not cut, tear, or damage the patch. If damaged, discard and apply a new patch at a different site. · Do not take other opioid medications or central nervous system depressants (e.g., alcohol, benzodiazepines) without consulting your doctor. · Serious side effects include slowed or difficult breathing, extreme drowsiness, dizziness, confusion, or feeling faint. Seek emergency medical help immediately. · Store patches out of reach of children and pets. After removal, fold the patch in half with adhesive sides together and flush down the toilet or return to a collection site. · Do not stop using this medication suddenly without talking to your doctor to avoid withdrawal symptoms. |