3. Old stuff
          3.1. Old pharm stuff (pre 2009)
              3.1.3. Pharmacology
                  3.1.3.5. Opioids
                      3.1.3.5.3. Opioid agonists
                          3.1.3.5.3.9. Other opioid agonists
 3.1.3.5.3.9.4. Propoxyphene 

Propoxyphene

[SH4:p116; NPS July 2003 PPR 22]

Usage

  • Mild to moderate pain not adequately relieved by aspirin
    * The only clinical usage
    * Used in some popular pain-relievers such as di-gesic, capadex

Structure

  • Structurally similar to methadone

Pharmacodynamics

Mechanism of action

  • Binds to classic opioid receptors

Effects

  • Does not have antipyretic or antiinflammatory effects
  • No significant antitussive activity
  • Analgesia
    * Oral doses 90-120mg produces analgesia and CNS effects like codeine 60mg + aspirin 650mg

Side-effects

  • Most common side effects
    * Vertigo
    * Sedation
    * N&V
  • Respiratory depression
    * 1/3 as potent as codeine in depressing ventilation
  • Overdose
    --> Seizures and ventilation depression
  • Mild withdrawal syndrome possible
  • Similar abuse potential as codeine
  • IV administration produce severe damage to veins
  • Dependency possible

Pharmacokinetics

Absorption

  • Completely absorbed from oral administration
    * But still poor bioavailability due to high first-pass hepatic metabolism

Metabolism

  • High first-pass hepatic metabolism
  • Propoxyphene is demethylated to norpropoxyphene

Elimination

  • Elimination half-time = 14.5 hours

Clinical

Avoid paracetamol/dextropropoxyphene combinations (e.g. capadex, Di-Gesic, Paradex)
--> No more effective than paracetamol alone
* [NPS]