Comparative Pharmacology
Head-to-head clinical analysis: DARVON versus ORAMORPH SR.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DARVON versus ORAMORPH SR.
DARVON vs ORAMORPH SR
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. Binding to mu-opioid receptors in the central nervous system (CNS) and peripheral tissues results in analgesia, euphoria, sedation, respiratory depression, and physical dependence. Morphine also activates descending inhibitory pathways and inhibits ascending nociceptive transmission.
Propoxyphene hydrochloride (Darvon) for moderate to severe pain: 65 mg orally every 4 hours as needed; maximum 390 mg/day.
10-30 mg orally every 8-12 hours, sustained-release; titrate as needed for pain.
None Documented
None Documented
6-12 hours (parent drug); norpropoxyphene half-life 30-36 hours, accumulates with repeated dosing, increasing risk of toxicity.
2–4 hours in adults; in controlled-release formulation, effective half-life is prolonged due to sustained absorption. Clinically, steady-state is achieved in 1–2 days.
Primarily hepatic metabolism to norpropoxyphene, then renal excretion of metabolites; <20% excreted unchanged in urine; minor biliary/fecal elimination.
Renal (approximately 90% as morphine-3-glucuronide and morphine-6-glucuronide, minor amounts of unchanged morphine, and other conjugates); biliary/fecal (approximately 10%).
Category C
Category C
Opioid Analgesic
Opioid Analgesic