Comparative Pharmacology
Head-to-head clinical analysis: FENTANYL versus WESTADONE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: FENTANYL versus WESTADONE.
FENTANYL vs WESTADONE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Fentanyl is a synthetic opioid that primarily acts as a μ-opioid receptor agonist. It binds to μ-opioid receptors in the central nervous system (CNS), leading to G-protein-coupled receptor activation, inhibition of adenylate cyclase, decreased cAMP production, and modulation of ion channels (e.g., increased potassium efflux, decreased calcium influx). This results in hyperpolarization of neurons and reduced neurotransmitter release, producing analgesia, sedation, and euphoria. Fentanyl also has high lipid solubility, allowing rapid CNS penetration and a fast onset of action.
Mu-opioid receptor agonist; also acts as an NMDA receptor antagonist and inhibits serotonin and norepinephrine reuptake.
25-100 mcg IV every 1-2 hours as needed; 50-100 mcg IM every 1-2 hours; transdermal patch: 12.5-100 mcg/h every 72 hours; transmucosal: 200-1600 mcg as single dose.
Oral: 2.5-10 mg every 4-6 hours as needed for pain; maximum 40 mg per day.
None Documented
None Documented
Clinical Note
moderateFentanyl + Torasemide
"The risk or severity of adverse effects can be increased when Fentanyl is combined with Torasemide."
Clinical Note
moderateFentanyl + Etacrynic acid
"The risk or severity of adverse effects can be increased when Fentanyl is combined with Etacrynic acid."
Clinical Note
moderateFentanyl + Furosemide
"The risk or severity of adverse effects can be increased when Fentanyl is combined with Furosemide."
Clinical Note
moderateFentanyl + Bumetanide
Terminal elimination half-life is 3–12 hours (mean ~7 hours) in adults; prolonged in elderly, hepatic impairment, or with continuous infusion due to context-sensitive half-life.
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 norfentanyl and other inactive metabolites; renal excretion of metabolites accounts for ~75% of the dose (10% unchanged), with ~9% excreted in feces.
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
"The risk or severity of adverse effects can be increased when Fentanyl is combined with Bumetanide."