For the treatment of cancer patients with severe pain that breaks through their regular narcotic therapy.
Opiate receptors are coupled with G-protein receptors and function as both positive and negative regulators of synaptic transmission via G-proteins that activate effector proteins. Binding of the opiate stimulates the exchange of GTP for GDP on the G-protein complex. As the effector system is adenylate cyclase and cAMP located at the inner surface of the plasma membrane, opioids decrease intracellular cAMP by inhibiting adenylate cyclase. Subsequently, the release of nociceptive neurotransmitters such as substance P, GABA, dopamine, acetylcholine and noradrenaline is inhibited. Opioids also inhibit the release of vasopressin, somatostatin, insulin and glucagon. Fentanyl's analgesic activity is, most likely, due to its conversion to morphine. Opioids close N-type voltage-operated calcium channels (OP2-receptor agonist) and open calcium-dependent inwardly rectifying potassium channels (OP3 and OP1 receptor agonist). This results in hyperpolarization and reduced neuronal excitability.
Fentanyl has an LD50 of 3.1 milligrams per kilogram in rats, and, 0.03 milligrams per kilogram in monkeys. The LD50 in humans is not known.
Bioavailability is 92% following transdermal administration and 50% following buccal administration.
7 (range 3-12) hours
Fentanyl is metabolized primarily via human cytochrome P450 3A4 isoenzyme system and mostly eliminated in urine. Within 72 hours of IV fentanyl administration, approximately 75% of the dose is excreted in urine, mostly as metabolites with less than 10% representing unchanged drug.
* 3 to 8 L/kg [Surgical Patients] * 0.8 to 8 [Hepatically Impaired Patients]
* 27 – 75 L/h [Surgical Patients receving IV administration] * 3 – 80 L/h [Hepatically Impaired Patients receving IV administration] * 30 – 78 L/h [Renally Impaired Patients receving IV administration]