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

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.