Comparative Pharmacology
Head-to-head clinical analysis: DARVON W ASA versus ULTRACET.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DARVON W ASA versus ULTRACET.
DARVON W/ ASA vs ULTRACET
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination analgesic: propoxyphene is a weak opioid agonist binding to mu-opioid receptors, inhibiting ascending pain pathways; aspirin irreversibly inhibits cyclooxygenase-1 and -2, reducing prostaglandin synthesis.
ULTRACET is a combination of tramadol (a centrally acting opioid agonist) and acetaminophen (a centrally acting analgesic with antipyretic effects). Tramadol binds to mu-opioid receptors and inhibits norepinephrine and serotonin reuptake. Acetaminophen's mechanism is not fully understood but involves inhibition of cyclooxygenase (COX) enzymes in the central nervous system.
1 capsule (propoxyphene HCl 65 mg / aspirin 650 mg) orally every 4 hours as needed for pain, not to exceed 6 capsules per day.
1-2 tablets (37.5 mg tramadol/325 mg acetaminophen per tablet) orally every 4-6 hours as needed for pain, not to exceed 8 tablets per day.
None Documented
None Documented
Propoxyphene terminal half-life is 6–12 hours (mean 8 h) in healthy adults; prolonged in hepatic impairment or elderly due to reduced metabolism. Aspirin half-life is 15–20 minutes due to rapid hydrolysis to salicylate.
Tramadol: 5.1 ± 0.9 hours (range 4-6 hours) for the parent drug; the active M1 metabolite has a half-life of 6.7 ± 1.7 hours. In hepatic impairment, tramadol half-life increases ~2-3 fold. Acetaminophen: 2-3 hours (range 1.25-3 hours); prolonged in overdose.
Renal elimination of propoxyphene and its metabolites accounts for ~70% of a dose, with ~20% excreted unchanged in urine; biliary/fecal elimination accounts for ~10%; aspirin is renally excreted as salicylate and its conjugates.
Tramadol and its metabolites are primarily excreted via the kidneys (approximately 90% of the dose), with about 30% excreted as unchanged drug and 60% as metabolites. Approximately 10% is excreted in feces. Acetaminophen is primarily conjugated in the liver and excreted renally as glucuronide (60-80%) and sulfate (20-30%) conjugates, with about 5% excreted unchanged.
Category C
Category C
Opioid Analgesic Combination
Opioid Analgesic Combination