Comparative Pharmacology
Head-to-head clinical analysis: DARVON versus MEPERGAN.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DARVON versus MEPERGAN.
DARVON vs MEPERGAN
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.
Meperidine is a synthetic opioid agonist that binds to mu-opioid receptors in the central nervous system, mimicking endogenous endorphins to produce analgesia. Promethazine is a phenothiazine antipsychotic that antagonizes histamine H1, dopamine D2, muscarinic acetylcholine, and alpha-adrenergic receptors, providing sedation and antiemetic effects.
Propoxyphene hydrochloride (Darvon) for moderate to severe pain: 65 mg orally every 4 hours as needed; maximum 390 mg/day.
Meperidine 50-100 mg and promethazine 25-50 mg IM/IV every 3-4 hours as needed. Maximum meperidine dose: 600 mg/day.
None Documented
None Documented
6-12 hours (parent drug); norpropoxyphene half-life 30-36 hours, accumulates with repeated dosing, increasing risk of toxicity.
Meperidine: 3-4 hours (terminal; increased in hepatic impairment). Promethazine: 9-16 hours (terminal; prolonged in elderly).
Primarily hepatic metabolism to norpropoxyphene, then renal excretion of metabolites; <20% excreted unchanged in urine; minor biliary/fecal elimination.
Renal elimination of metabolites (meperidine: ~90% as metabolites, <5% unchanged; promethazine: ~70-80% as metabolites, <1% unchanged). Biliary/fecal excretion is minimal (<10% for both).
Category C
Category C
Opioid Analgesic
Opioid Analgesic/Antiemetic Combination