Dextromethorphan Addiction Mediated Through the NMDA System: Common Pathways With Alcohol?

A 45-year-old woman with dextromethorphan use disorder experienced intense cravings that prevented abstinence. Treatment with topiramate, chosen because both drugs act on the NMDA system, eliminated her cravings completely. Genetic testing revealed she carried the GRIK1 rs2832407(C:C) allele, which is linked to increased risk of alcohol use disorder and positive response to topiramate in heavy drinkers. This case illustrates personalized medicine using genetic testing and suggests possible shared genetic susceptibility for dependence across different substances.

Study at a glance

Abstract

Dextromethorphan, an antitussive (cough suppressant) drug of the morphinan class with sedative and dissociative properties found in cough syrup and other over-the-counter products, is also a substance of abuse, seen primarily in young adults all over the world. A case of dextromethorphan use disorder is presented in a 45-year-old women. Her repeated attempts at abstinence were unsuccessful secondary to continued intense cravings. Treatment with topiramate resulted in complete resolution of her cravings. Topiramate was chosen empirically because of a common action with dextromethorphan in the NMDA system. Genetic testing was obtained and the patient was found to be a carrier of the GRIK1 rs2832407(C:C) allele. The (C:C) allele has been associated with an increased risk of alcohol use disorder and a treatment response of patients with heavy drinking to topiramate. This case provides an opportunity to discuss personalized medicine (treatment options aided by the use of genetic testing) and the possible shared genetic susceptibility for dependence in 2 substances of abuse.