Alan B. Storrow, Michael Magoon, Glenn Mitchell, Joint Military Medical Centers Emergency Medicine Residency, San Antonio, Texas.
Since dextromethorphan is structurally related to opiates, people undergoing urine drug screenings have claimed it has produced falsely positive results.
To determine if a single oral dose of dextromethorphan liquid would produce a falsely positive qualitative urine opiate screening.
Prospective, randomized, triple-blinded, crossover drug protocol.
Urban Level I emergency department.
Twenty adult volunteers, who did not take routine medications, were not pregnant, were without known sensitivity to dextromethorphan, and were negative for urine toxicologic screening immediately prior to testing.
Fifteen male and five female volunteers (mean age 30.7) underwent three separate urine enzyme-multiplied immunoassay technique (EMIT) opiate screenings (Syva Co., San Jose, CA) Each screening was performed six hours after ingestion of a single liquid medication, either dextromethorphan, codeine, or placebo. Each volunteer took all three medications randomly, at least three days 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.
Six hours after ingestion of dextromethorphan at both dosage levels, all of the urine EMIT assays were negative for opiates and all other drugs. This demonstrates with 95% confidence that, at most, 16% of the population could expect to have a positive opiate screening after ingestion. After codeine and placebo ingestion, all assays were positive and negative for opiates, respectively.
Although dextromethorphan is structurally similar to opiates, the ingestion of a single normal (or even twice normal) dose of dextromethorphan is not likely to produce a falsely positive six-hour urine opiate screening.