Comparative Pharmacology
Head-to-head clinical analysis: DARVON N versus FENTORA.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DARVON N versus FENTORA.
DARVON-N vs FENTORA
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Propoxyphene is a weak mu-opioid receptor agonist that produces analgesia by binding to opioid receptors in the central nervous system, altering the perception of and response to pain. Its metabolite norpropoxyphene has local anesthetic and sodium channel blocking effects, which may contribute to cardiac toxicity.
Fentanyl is a potent mu-opioid receptor agonist, binding to and activating opioid receptors in the brain and spinal cord, leading to analgesia and sedation.
100 mg orally every 4 hours as needed for pain; maximum 600 mg per day.
For opioid-tolerant adults: 100 mcg (one tablet) placed in buccal cavity; titrate upward in increments of 100 mcg per breakthrough pain episode, with minimum 2-hour interval between doses; maximum 4 doses per day.
None Documented
None Documented
Propoxyphene: 6-12 hours; norpropoxyphene: 30-36 hours. Accumulation of norpropoxyphene on repeated dosing increases risk of toxicity.
Terminal elimination half-life is approximately 2–4 hours in adults, but can range from 2 to 6 hours depending on hepatic clearance. In elderly or hepatically impaired patients, half-life may be prolonged. The rapid initial decline is due to redistribution, and the terminal phase reflects slow elimination from deep compartments.
Primarily renal (approximately 70% as unchanged drug and glucuronide conjugates); minor biliary/fecal elimination (25-30%).
Primarily renal: Approximately 75% of the dose is excreted in urine as metabolites (mostly norfentanyl, despropionylfentanyl, and hydroxyfentanyl), with less than 7% as unchanged fentanyl. Fecal elimination accounts for about 9%.
Category C
Category C
Opioid Analgesic
Opioid Analgesic