Comparative Pharmacology
Head-to-head clinical analysis: DARVON versus INFUMORPH.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DARVON versus INFUMORPH.
DARVON vs INFUMORPH
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Propoxyphene is a mu-opioid receptor agonist that inhibits ascending pain pathways by binding to opioid receptors in the CNS, altering pain perception. It also has weak local anesthetic effects.
Morphine is a full opioid agonist with relative selectivity for the mu-opioid receptor, although it can interact with other opioid receptors at higher doses. It mimics endogenous endorphins by binding to opioid receptors in the CNS, causing inhibition of ascending pain pathways and altering pain perception.
Propoxyphene hydrochloride (Darvon) for moderate to severe pain: 65 mg orally every 4 hours as needed; maximum 390 mg/day.
Morphine sulfate 10-30 mg orally every 4 hours as needed; or 2.5-15 mg IV/IM/SC every 2-6 hours; or 0.5-2 mg per hour continuous IV infusion. Extended-release formulations: 15-30 mg orally every 8-12 hours.
None Documented
None Documented
6-12 hours (parent drug); norpropoxyphene half-life 30-36 hours, accumulates with repeated dosing, increasing risk of toxicity.
Terminal elimination half-life: 2–4 hours in healthy adults; prolonged to 4–6 hours in the elderly or those with renal impairment, leading to accumulation of active metabolites (M6G).
Primarily hepatic metabolism to norpropoxyphene, then renal excretion of metabolites; <20% excreted unchanged in urine; minor biliary/fecal elimination.
Renal elimination of morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) accounts for approximately 90% of total clearance, with <10% excreted as unchanged morphine in urine. Biliary/fecal elimination accounts for the remaining fraction (<10%).
Category C
Category C
Opioid Analgesic
Opioid Analgesic