Dextromethorphan is a synthetic codeine analog that acts as a weak opioid receptor agonist.
Dextromethorphan acts as a weak opioid agonist and therefore its opioid effects and the potential for addiction are low compared to other opioids. If an overdose occurs, it can be treated with naloxone.
Another unique mechanism of this drug is antagonism on NMDA receptors. NMDA receptors are ionotropic receptors that depolarize the neuron in response to activation by glutamate. Since this drug acts as an excitatory amino acid antagonist, it prevents neuronal damage and modulates pain sensation.
Dextromethorphan is primarily used as a cough suppressant and can be found in many over-the-counter cough syrups. This is accomplished by depressing the medullary cough center through sigma receptor stimulation.
Since dextromethorphan inhibits serotonin reuptake, patients are at increased risk of serotonin syndrome, especially if they are taking serotonergic medications such as SSRIs.
Although rare, drug overdose is possible in patients taking huge quantities of dextromethorphan.
Dextromethorphan poisoning is uncommon and in rare cases can be associated with respiratory depression, especially in young children. In severe cases of dextromethorphan overdose, naloxone can be considered given its antagonistic action on opioid receptors.
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