Dextromethorphan Abuse

CMAJ Practice

Five things to know about … Dextromethorphan abuse

Tony Antoniou PhD, David N. Juurlink MD PhD

Dextromethorphan is more Use is increasing among adolescents Box 1: “Plateaus” of dextromethorphan than an innocuous antitussive toxicity*2,3 According to the Ontario Student Drug At large doses used recre- Plateau 1 (1.5–2.5 mg/kg) Use and Health Survey, 9.7% of stu- ationally (300 to > 1500 mg), • Total intake 100–200 mg (4–6 capsules or dents in grades 7 to 12 reported using dextromethorphan and its 35–60 mL of syrup) dextromethorphan recreationally in metabolite dextrophan block • Restlessness, euphoria 2013, compared with 6.9% in 2011.5 N-methyl-d-aspartate recep- Plateau 2 (2.5–7.5 mg/kg) Most dextromethorphan-related calls to tors, producing dissociative • Total dose 200–500 mg (7–18 capsules or poison control centres involve adoles- effects similar to those of 60–185 mL of syrup) cent males and solid dose formulations 1 6 phencyclidine and ketamine. • Exaggerated auditory and visual sensations, of the drug. 2 Neurobehavioural effects can closed-eye hallucinations, imbalance begin within one hour after ingestion, are dose-related and Plateau 3 (7.5–15 mg/kg) are described by users as • Total dose 500–1000 mg (18–33 capsules or Withdrawal can occur 185–375 mL of syrup) occurring in “plateaus” (Box 2,3 • Visual and auditory disturbances, altered 1). Adrenergic effects (e.g., consciousness, delayed reaction times, Anecdotal reports from long-term hypertension,1 diaphoresis) can mania, panic, partial dissociation users (i.e., months to years) have result from dose-related inhib described intense cravings, flash- ition of catecholamine reup- Plateau 4 (> 15 mg/kg) backs and hallucinations within take, and serotonergic effects • Total dose > 1000 mg (> 33 capsules or three days after stopping dextro can result from agonist effects > 375 mL of syrup) methorphan.2,3 Physical symptoms of at serotonin receptors.4 Sero- • Hallucinations, delusions, ataxia, complete withdrawal include diarrhea, vomit- dissociation tonin syndrome can also arise ing and rigors. Symptoms typically from interactions with seroto- *Assuming a 75-kg person, 30-mg capsules and 3 mg per resolve within two days without spe- millilitre of syrup. 2,3 51 nergic drugs. cific treatment.

Treatment is supportive See references, Appendix 1, www.cmaj.ca Clinical effects may be influenced /lookup/suppl/doi:10.1503/cmaj.131676/-/DC1 by combined-formulation drugs No specific antidote exists for dextro methorphan toxicity.3,5 Guidelines sug- Some effects attributed to dextro gest benzodiazepines for seizures and Competing interests: None declared. methorphan may reflect ingestion of aggressive cooling measures for hyper- This article has been peer reviewed. combination drugs, particularly thermia. Naloxone can be considered for Affiliations: Department of Family and Com decongestants, acetaminophen and use in patients in a coma or with respira- munity Medicine (Antoniou), St. Michael’s Hospi- anticholinergic antihistamines.2,4 tory depression, although clinical tal; Department of Family and Community Medi- Because dextromethorphan is not response is varied.2,4 Acetaminophen lev- cine (Antoniou), University of Toronto; Institute detected by basic drug screens, tox- els should be obtained when concomitant for Clinical Evaluative Sciences (Juurlink); Department of Medicine (Juurlink), Sunnybrook icity secondary to its use should be ingestion is suspected, and additional Health Sciences Centre, Toronto, Ont. considered 3when evaluating patients measures for4 the management of associ- 2,4 Correspondence to: Tony Antoniou, tantoniou with a dissociative toxidrome. ated complications (e.g., delayed hepatic @smh.ca injury related to acetaminophen over- dose) implemented as appropriate.2,4 CMAJ 2014. DOI:10.1503/cmaj.131676