The dextromethorphan defense: dextromethorphan and the opioid screen

Abstract

Objective: To determine whether a single oral dose of dextromethorphan produces a falsely positive qualitative urine opioid screen.

Methods: A prospective, randomized, triple-blind, placebo-controlled, crossover exposure study design was used. Twenty adult volunteers participated. All were without routine medications, not pregnant or lactating, without known sensitivity to dextromethorphan, and negative for urine toxicologic screening immediately prior to testing. These volunteers underwent three separate urine Enzyme-Multiplied Immunoassay Technique (EMIT) opioid screens. Each screen was performed six hours after the subject had ingested a single liquid medication, either dextromethorphan, codeine, or placebo. Each volunteer took all three medications randomly, at least 72 hours apart. Half of the volunteers took the standard adult dose of dextromethorphan (20 mg), while the other half ingested twice this amount (40 mg). The amounts of codeine (30 mg) and sucrose placebo (10 mL) remained constant.

Results: For these young adults (mean age +/- SD = 30.7 +/- 2.8 years), all urine EMIT assays six hours after ingestion of dextromethorphan, at both dosage levels, were negative for opioids and all other drugs. All assays after codeine and placebo ingestion were positive and negative for opioids, respectively.

Conclusion: Although dextromethorphan is structurally similar to opioid drugs, the ingestion of a single normal (or even twice normal) dose of dextromethorphan is not likely to produce a falsely positive six-hour urine opioid EMIT screen.