Successful treatment of dextromethorphan use disorder with combined naltrexone and gabapentin: a case report

A case report describes a young person with dextromethorphan (DXM) use disorder, arising from misuse of NyQuil, which contains DXM, acetaminophen, doxylamine, and alcohol. DXM, related to codeine and ketamine, produces dissociative effects at high doses and has addiction liability. The patient was successfully treated with a combination of naltrexone and gabapentin, targeting NMDA and sigma-1 receptors involved in DXM's mechanism. The report suggests this combination may be a viable treatment for DXM addiction.

Study at a glance

Abstract

NyQuil is an over-the-counter medication containing the pain reliever, acetaminophen; the antihistamine, doxylamine; and dextromethorphan (DXM), the antitussive medication. The Nyquil liquid formulation also contains alcohol, listed among the inactive ingredients. DXM has dependence-producing properties and addiction liability, especially in young people (1). Large doses (>1500 mg/day) can produce dissociative effects similar to ketamine (2). DXM is the methylated d-isomer of levorphanol, a substance related to codeine (3). The active metabolite, dextrorphan, is a noncompetitive NMDA-R antagonist and a sigma-1 receptor agonist (3). Interestingly, DXM overdose has been successfully treated with naloxone, a μ-opioid receptor antagonist (4). Given DXM’s mechanism of action at both NMDA and sigma-1 receptors, it may be possible to treat DXM addiction by targeting these receptors. Moreover, the anti-histamine doxylamine may contribute to the actions of Nyquil. We present a case-report on DXM use disorder treated with the combination of naltrexone and gabapentin.