Methamphetamine and Amphetamine Isomer Concentrations in Human Urine Following Controlled Vicks VapoInhaler Administration

Legitimate use of legal intranasal decongestants containing L-methamphetamine may complicate interpretation of urine drug tests positive for amphetamines. Our study hypotheses were that commonly used immunoassays would produce no false-positive results and a recently developed enantiomer-specific gas chromatography‐mass spectrometry (GC‐MS) procedure would find no D-amphetamine or D-methamphetamine in urine following controlled Vicks VapoInhaler administration at manufacturer’s recommended doses. To evaluate these hypotheses, 22 healthy adults were each administered one dose (two inhalations in each nostril) of a Vicks VapoInhaler every 2 h for 10 h on Day 1 (six doses), followed by a single dose on Day 2. Every urine specimen was collected as an individual void for 32 h after the first dose and assayed for D -a ndL-amphetamines specific isomers with a GC‐MS method with >99% purity of R-(2)-a-methoxy-a-(trifluoromethyl)phenylacetyl derivatives and 10 mg/L lower limits of quantification. No D-methamphetamine or D-amphetamine was detected in any urine specimen by GC‐MS. The median L-methamphetamine maximum concentration was 62.8 mg/L (range: 11.0‐1,440). Only two subjects had detectable L-amphetamine, with maximum concentrations coinciding with L-methamphetamine peak levels, and always � 4% of the parent’s maximum. Three commercial immunoassays for amphetamines EMIT w II Plus, KIMS w II and DRI w had sensitivities, specificities and efficiencies of 100, 97.8, 97.8; 100, 99.6, 99.6 and 100, 100, 100%, respectively. The immunoassays had high efficiencies, but our first hypothesis was not affirmed. The EMIT w II Plus assay produced 2.2% false-positive results, requiring an enantiomer-specific confirmation.