DXM

Dextromethorphan (DXM) is a medication used as an antitussive in many over-the-counter cough preparations. It is a non-opioid cough suppressant in the morphinan family, included in syrups, tablets, and gels. Therapeutic doses relieve cough without providing analgesia or strong sedation for most adults. At much higher doses, it can produce dissociative and hallucinogenic effects.

DXM acts mainly as an antagonist of the NMDA receptor. It is metabolized in the liver by CYP2D6 to dextrorphan, which also has dissociative properties and may contribute to psychotropic effects. DXM can weakly inhibit the reuptake of serotonin and norepinephrine and interact with sigma-1 receptors. These pharmacologic actions underlie both its therapeutic effects and potential adverse effects.

Therapeutic use is generally safe when used as directed. Common side effects include dizziness, drowsiness, nausea, and mouth dryness. At high doses, symptoms may include confusion, impaired motor function, rapid heartbeat, high or low blood pressure, hyperthermia, and, in severe cases, seizures or coma.

High-dose use increases risk of serotonin syndrome when combined with other serotonergic drugs. DXM has a history of misuse as a recreational dissociative, sometimes in large amounts or in combination products, leading to emergency department visits and regulatory concerns.

DXM can interact with monoamine oxidase inhibitors (MAOIs) and other serotonergic agents, raising the risk of hypertensive crisis or serotonin syndrome. It should be used with caution in people with liver disease, psychiatric illness, or those taking other CNS depressants, and is generally advised not to combine it with alcohol.

Legally, DXM is available over-the-counter in many countries, but sale to minors and limits on package sizes exist in various places. As with other cough medicines, it is important to follow dosing instructions and seek medical attention for signs of overdose or adverse reactions.