Tramadol

Tramadol is an analgesic agent with a complicated mechanism of action:

  • Action at all opioid receptors, but particularly MOP, causing analgesia as well as nausea and vomiting
  • Inhibits 5-HT reuptake which provides descending inhibitory analgesia
  • Inhibits NA reuptake descending inhibitory analgesia
  • NMDA receptor antagonist
Properties Tramadol
Class Cyclohexanol derivative. Racemic mixture of (+)Tramadol which has greater MOP and 5HT reuptake effects, and (-)Tramadol, which mediates NA reupake inhibition
Uses Analgesia
Presentation Racemic mixture - each isomer has complementary effects. IV solution is clear at 50mg.ml-1
Route of Administration PO/IV/Topical
Dosing 50-100mg QID. Potency 1/5th that of morphine.
Absorption Bioavailability 70%
Distribution VD 4L.kg-1
Metabolism Hepatic to active and inactive metabolites
Excretion Urinary of predominantly inactive metabolites, t1/2β 300 minutes
Respiratory Minimal respiratory depression
CVS Avoid concominant MAO-I use given NA reuptake inhibition
CNS Increased seizure risk in those with epilepsy or concurrent SSRI/SNRI/TCA use. Minimal addiction potential
GIT N/V

References

  1. Peck TE, Hill SA. Pharmacology for Anaesthesia and Intensive Care. 4th Ed. Cambridge University Press. 2014.
Last updated 2017-09-23

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