Dextromethorphan/levomethorphan issues in a case of opiate overdose

摘要

Dextromethorphan is the c/-isomer of 3-methoxy-N-methylmorphinan (methorphan), a synthetic analogue of codeine. It interacts with the a-opioid receptors with resulting antitussive activity, while it does not show any significant affinity for the i and 8 opioid receptors, which are responsible for analgesic and central nervous system depressant effects. On this basis, d-methorphan is widely used all over the world as an over-the-counter cough suppressant drug. Indeed, there are hundreds of cough and cold preparations containing d-methorphan alone or in combination with analgesic (acetaminophen, acetyl salicylic acid), decongestant (phenylephrine, pseudoephedrine), anthistaminic (chlorpheniramine, brompheniramine, pheniramine), and/or expectorant mucolytic agents. In large doses, d-methorphan and its metabolite dextrorphan antagonize the actions of excitatory amino acids on N-methyl-d-aspartate (NMDA) receptors as do phencyclidine and ketamine.