Chapter 16 - Critical Issues When Testing for Amphetamine-Type Stimulants: Pitfalls of Immunoassay Screening and Mass Spectrometric Confirmation for Amphetamines, Methamphetamines, and Designer Amphetamines

Abstract

Amphetamine and methamphetamine are not only widely abused but these drugs along with certain drugs, which are metabolized to amphetamine or methamphetamine (which is further metabolized to amphetamine) are also used for treating narcolepsy, attention-deficit disorders in children over age 6 years, as well as short-term treatment of obesity. Immunoassays are commonly employed to screen for the presence of amphetamine/methamphetamine, but many over-the-counter drugs, most commonly ephedrine/pseudoephedrine interfere with immunoassays causing false-positive test results. However, analytical test results may also occur after taking prescription medications that are metabolized to amphetamine or methamphetamine. Moreover, l-isomer of methamphetamine is present in Vick’s inhaler while d-methamphetamine is abused. Although recommended use of Vick’s inhaler should not produce positive test result with amphetamine/methamphetamine immunoassay due to stereospecificity of antibody, excess use of Vick’s inhaler may cause positive test result. In that situation gas chromatography–mass spectrometry analysis using chiral derivatization must be used to confirm methamphetamine abuse.