Comparative Pharmacology
Head-to-head clinical analysis: DARVOCET versus DARVON N W ASA.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DARVOCET versus DARVON N W ASA.
DARVOCET vs DARVON-N W/ ASA
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Darvocet is a combination of propoxyphene, a mu-opioid receptor agonist that alters perception of and response to pain, and acetaminophen, which inhibits COX enzymes and modulates descending serotonergic pathways.
Propoxyphene is a weak opioid agonist that binds to mu-opioid receptors in the CNS, altering pain perception. Aspirin inhibits cyclooxygenase (COX-1 and COX-2), reducing prostaglandin synthesis, which mediates pain, fever, and inflammation.
1 tablet (propoxyphene 100 mg / acetaminophen 650 mg) orally every 4 hours as needed for pain; maximum 6 tablets per day.
1-2 capsules (propoxyphene napsylate 100 mg / aspirin 325 mg per capsule) orally every 4 hours as needed for pain; maximum 6 capsules per day.
None Documented
None Documented
Propoxyphene: 6-12 hours (parent), 30-36 hours (norpropoxyphene). Acetaminophen: 1-4 hours (therapeutic doses). Accumulation of norpropoxyphene occurs with repeated dosing.
Propoxyphene: terminal elimination half-life is 6-12 hours in adults with normal renal function; norpropoxyphene has a longer half-life (30-36 hours). Aspirin (as salicylate): half-life is dose-dependent, ranging from 2-3 hours at low doses to 15-30 hours at anti-inflammatory doses (300-600 mg in Darvon-N W/ASA).
Propoxyphene: primarily hepatic metabolism to norpropoxyphene, renal excretion of metabolites (<1% unchanged). Acetaminophen: renal excretion of conjugates (85-90%) and unchanged drug (2-4%).
Renal: propoxyphene and its metabolites (norpropoxyphene) are primarily eliminated via kidneys, with ~20-25% excreted unchanged; fecal: minor; biliary: some enterohepatic recirculation occurs, but exact % are not well quantified for the combination product. Aspirin is hydrolyzed to salicylate, which is excreted renally (75% as salicyluric acid, 10% as salicylic acid, 10% as glucuronide conjugates, and minor amounts as gentisic acid).
Category C
Category C
Opioid Analgesic Combination
Opioid Analgesic Combination