Brand names: Darvon, Darvocet, plus many others
Propoxyphene was often formulated together with acetaminophen, aspirin or other analgesic. It was found that propoxyphene provided little additional analgesic effect over its partner, whiling having an abuse potential and significant toxicity.
Toxic levels were related to both the parent drug and toxic metabolite (norpropoxyphene). Both propoxyphene and norpropoxyphene have a long half-life (4-24 hours, 24-34 hours).
Toxic levels could be achieved by:
(1) accumulation with chronic use, especially in the elderly or with chronic liver disease
(2) suicidal intent
(3) accidental, often at seemingly low doses
Toxic effects include:
(1) vomiting
(2) prolongation of the QT interval with torsades de pointes
(3) other cardiac arrhythmias
(4) hypoglycemia
(5) seizures
(6) diabetes insipidus
(7) respiratory depression
(8) cardiovascular collapse
(9) coma
While naloxone can reverse some of the toxic effects, large doses may be needed and the reversal may be incomplete. In addition, rebound in symptoms can occur as the naloxone is eliminated.
Additional concerns:
(1) toxic effects of acetaminophen if a drug combination ingested
(2) additive effects of alcohol or other CNS depressants
