FENTANYL CITRATE PRESERVATIVE FREE
Clinical safety rating: avoid
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur.
Synthetic opioid agonist; primarily binds to mu-opioid receptors in the CNS, modulating nociceptive pathways and producing analgesia, sedation, and euphoria.
| Metabolism | Primarily hepatic via CYP3A4 oxidation to norfentanyl and other inactive metabolites; minor N-dealkylation. Clearance may be reduced in hepatic impairment. |
| Excretion | Primarily hepatic metabolism via CYP3A4, with approximately 75% of the dose excreted in urine as metabolites (primarily norfentanyl) and <10% as unchanged fentanyl. About 9% is excreted in feces. Minimal biliary excretion. |
| Half-life | Terminal elimination half-life is approximately 2–4 hours in healthy adults, but may be prolonged to 4–12 hours in elderly, critically ill, or obese patients due to increased volume of distribution and decreased clearance. Context: Duration of action after a single bolus is relatively short due to redistribution, but accumulation can occur with repeated doses or infusions, leading to prolonged effects. |
| Protein binding | Approximately 80–85% bound, primarily to alpha-1-acid glycoprotein, and to a lesser extent albumin. Binding is saturable and can be altered by disease states (e.g., increased in inflammation, decreased in hypoalbuminemia). |
| Volume of Distribution | Volume of distribution (Vd) is 3–6 L/kg (range 3–8 L/kg) in healthy adults. High Vd reflects extensive tissue distribution (e.g., fat, muscle) and lipophilicity. Context: Allows redistribution from brain to tissues, contributing to rapid offset of effect after single dose. |
| Bioavailability | Intravenous: 100% (all IV formulations have complete bioavailability). Intramuscular: approximately 90% (extensive absorption). Oral transmucosal (not applicable if preservative-free IV formulation is used; for reference: 50% for oral transmucosal due to first-pass metabolism). Transdermal: approximately 92% (not with this formulation; preservative-free is exclusively for IV/IM use). |
| Onset of Action | Intravenous: Immediate (30 seconds to 1 minute). Intramuscular: 5–15 minutes. Transdermal: Not applicable (preservative-free formulation typically IV). Onset is rapid due to high lipophilicity. |
| Duration of Action | Intravenous: 30–60 minutes after a single bolus due to redistribution; context: analgesia persists for about 0.5–1 hour. With continuous infusion, context-sensitive half-life increases with infusion duration (e.g., 3–4 hours after 8-hour infusion). Prolonged with hepatic impairment. |
Initial: 50-100 mcg IV every 2-5 minutes as needed for pain. For anesthesia: 2-50 mcg/kg IV bolus, then 0.7-10 mcg/kg/hr infusion.
| Dosage form | INJECTABLE |
| Renal impairment | No specific GFR-based dose adjustment required. Use with caution in severe renal impairment (CrCl < 30 mL/min) due to potential accumulation of metabolites; consider dose reduction of 50%. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Reduce dose by 50%. Child-Pugh C: Avoid or reduce dose by 75% with close monitoring. |
| Pediatric use | Children 2-12 years: Initial 1-2 mcg/kg IV every 2-4 hours as needed. Continuous infusion: 0.5-2 mcg/kg/hr. Adjust based on response. |
| Geriatric use | Elderly patients: Reduce initial dose by 50% (e.g., 25-50 mcg IV) and titrate slowly due to increased sensitivity and prolonged half-life. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur.
| FDA category | Positive |
| Breastfeeding | Enters breast milk in low concentrations; M/P ratio approximately 0.4. American Academy of Pediatrics considers compatible with breastfeeding; avoid if repeated doses or high maternal dose due to potential infant sedation and respiratory depression. |
| Teratogenic Risk | Fentanyl crosses placenta. First trimester: limited human data; animal studies show no teratogenicity at therapeutic doses, but high doses cause embryotoxicity. Second/third trimester: chronic use may cause fetal dependence and withdrawal; at delivery, may cause neonatal respiratory depression. |
■ FDA Black Box Warning
Risk of respiratory depression: life-threatening, especially in opioid-naive patients; requires resuscitation equipment. Risk of opioid addiction, abuse, and misuse. Accidental ingestion, especially in children, can be fatal. Concomitant use with CNS depressants (e.g., benzodiazepines) increases risk of profound sedation, respiratory depression, coma, and death. Neonatal Opioid Withdrawal Syndrome with prolonged use during pregnancy.
| Common Effects | Constipation |
| Serious Effects |
["Hypersensitivity to fentanyl or any component","Significant respiratory depression","Acute or severe bronchial asthma","Paralytic ileus","Concurrent use with MAOIs or within 14 days","Obstructive sleep apnea without monitoring"]
| Precautions | ["Respiratory depression: monitor ventilation, have naloxone available","Bradycardia and hypotension","Chest wall rigidity (especially with rapid IV administration)","Serotonin syndrome with serotonergic drugs","Adrenal insufficiency with prolonged use","Increased intracranial pressure (use cautiously)","Seizure risk in epilepsy","Biliary tract spasm","Tolerance and physical dependence","Avoid abrupt cessation"] |
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| Fetal Monitoring | Monitor maternal respiratory rate, oxygen saturation, sedation level, and pain score. Fetal heart rate monitoring during labor; neonatal observation for respiratory depression and opioid withdrawal. |
| Fertility Effects | Limited human data. Animal studies show no adverse effects on fertility at therapeutic doses. High doses may disrupt estrous cycles; opioid-induced hyperprolactinemia can impair ovulation. |