Comparative Pharmacology
Head-to-head clinical analysis: FENTANYL 100 versus WESTADONE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: FENTANYL 100 versus WESTADONE.
FENTANYL-100 vs WESTADONE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Fentanyl is a μ-opioid receptor agonist. It binds to μ-opioid receptors in the central nervous system, activating G-protein coupled receptor signaling (inhibition of adenylate cyclase, modulation of ion channels), leading to increased potassium conductance and decreased calcium influx, resulting in hyperpolarization and reduced neurotransmitter release. This produces analgesia, sedation, and respiratory depression.
Mu-opioid receptor agonist; also acts as an NMDA receptor antagonist and inhibits serotonin and norepinephrine reuptake.
100 mcg intravenously every 1-2 hours as needed for pain; or 100 mcg intramuscularly every 1-2 hours; transdermal patch: 12-100 mcg/hour applied every 72 hours; buccal tablet: 100-200 mcg as a single dose for breakthrough pain.
Oral: 2.5-10 mg every 4-6 hours as needed for pain; maximum 40 mg per day.
None Documented
None Documented
Terminal elimination half-life: 2–4 hours in adults; prolonged in elderly, hepatic impairment, or continuous infusion (due to redistribution).
Terminal elimination half-life: 15-60 hours (mean ~24 hours). Clinical context: Prolonged half-life supports once-daily dosing in opioid maintenance; accumulation occurs with repeated dosing due to long half-life.
Primarily hepatic metabolism to inactive metabolites (norfentanyl, etc.); ~75% excreted in urine as metabolites, ~9% in feces, <10% unchanged in urine.
Primarily renal (40-50% as unchanged methadone and its metabolites, 15-20% as metadone-N-oxide), biliary/fecal (5-10%).
Category D/X
Category C
Opioid Agonist
Opioid Agonist