Pfizer Fentanyl Citrate Mechanism of Action

Pharmacologic Category: Opioid Analgesic.
Pharmacology: Pharmacodynamics: Mechanism of action: Fentanyl is a synthetic opioid analgesic related to the phenylpiperidines such as morphine. As an analgesic it is estimated to be about 80 times more potent than morphine. As with morphine and pethidine in equianalgesic doses, fentanyl produces respiratory depression but there is a quicker return to normal respiration in healthy individuals.
Fentanyl unlike other phenylpiperidines rarely produces histamine release and exhibits little hypnotic activity.
Clinical trials: No data available.
Pharmacokinetics: Absorption: Following parenteral administration via intravenous or intramuscular injection the action of fentanyl is rapid. Peak analgesic effect occurs within several minutes and has a duration of 30 to 60 minutes following a single dose of up to 100 micrograms given intravenously. Respiratory depressant effects last longer than analgesia.
Distribution: After intravenous injection, serum concentrations of fentanyl have been shown to decrease rapidly to about 20% of peak concentrations within 5 minutes of injection, followed by a slower decrease over the next 10 to 20 minutes to stabilize at a low concentration for 2 hours after injection. The short duration of action is probably due to the redistribution with up to 70% being bound to plasma proteins.
Metabolism: Fentanyl is metabolized, mainly in the liver, to inactive metabolites norfentanyl, 4-N-anilinopiperidine and propionic acid. In vitro data show fentanyl is metabolized to norfentanyl mainly by CYP3A4.
Excretion: About 20% of the drug is excreted in the urine within 8 hours with up to 90% as the metabolites and 10% as unchanged fentanyl.
Toxicology: Preclinical Safety Data: Genotoxicity: No data available.
Carcinogenicity: No data available.