Comparative Pharmacology
Head-to-head clinical analysis: DARVON versus IONSYS.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DARVON versus IONSYS.
DARVON vs IONSYS
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.
IONSYS is an iontophoretic delivery system for fentanyl, a mu-opioid receptor agonist. Fentanyl binds to mu-opioid receptors in the CNS, inhibiting ascending pain pathways and altering pain perception and emotional response.
Propoxyphene hydrochloride (Darvon) for moderate to severe pain: 65 mg orally every 4 hours as needed; maximum 390 mg/day.
Apply one 40 mcg fentanyl iontophoretic transdermal system to skin on upper arm or chest; delivers 40 mcg per dose on-demand for up to 24 hours or 80 doses, whichever is shorter. Maximum 2 doses per hour, 6 doses per application. Patient must be opioid-tolerant.
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: 16.3 ± 9.1 hours for fentanyl released from IONSYS; accounts for prolonged release from depot and is longer than intravenous fentanyl (3-12 hours).
Primarily hepatic metabolism to norpropoxyphene, then renal excretion of metabolites; <20% excreted unchanged in urine; minor biliary/fecal elimination.
Renal: approximately 90% as fentanyl metabolites (mainly norfentanyl) and less than 10% as unchanged drug; fecal: less than 10%.
Category C
Category C
Opioid Analgesic
Opioid Analgesic