False positive for amphetamines, need help or my husband is gone?

and chemically related compounds (eg, pseudoephedrine),
have been shown to produce false-positive results, making
the amphetamine assay one of the most difficult tests to
interpret. The Figure illustrates common medications with
structures similar to amphetamines that can produce falsepositive
results.
Interpretation of amphetamine assays requires a detailed
medication history that includes over-the-counter, prescription,
and herbal medications. Pseudoephedrine, ephedrine,
phenylephrine, and decongestants common in overthe-
counter cold medicines are known to cross-react with
the amphetamine assay.39 Results of amphetamine assays
are often positive among patients taking prescription
stimulants for attention deficit and hyperactivity disorder,
for narcolepsy, and as anorexiants because many of these
stimulants contain amphetamines (Table 3). Many psychotropic
medications, such as bupropion,33,40 phenothiazines
(eg, chlorpromazine, promethazine, and thioridazine),29,34
trazodone,37 and TCAs (desipramine and doxepin),30,31 have
been reported to interfere with immunoassays. Most of
these reports attribute the cross-reactivity to metabolites
of these agents, which typically are not assessed in manufacturers’
evaluations of immunoassays for interference.
Other unique agents found to cross-react with the amphetamine
immunoassay include labetalol,23 isometheptene,
27 ranitidine,24,26,35 ritodrine,32 and trimethobenzamide.
22,25 Structural similarities are the main reasons for
the interference.
Another confounding factor for the amphetamine immunoassay
is the inability to distinguish between the 2
isomers of methamphetamine, d-methamphetamine and lmethamphetamine
(l-desoxyephedrine). The d-isomer is
responsible for the central nervous system stimulant effects,
whereas the l-isomer mainly works peripherally and
does not possess euphoric effects.15 Vicks nasal inhaler
contains l-methamphetamine and did cross-react with older
immunoassay tests when used in large quantities. Newer
EMIT tests have shown no positive results with the Vicks
nasal inhaler when used up to twice the recommended
dose.36 Additionally, selegiline and deprenyl, agents used
for the treatment of Parkinson disease and depression, produce
l-amphetamine and l-methamphetamine metabolites,
which give a positive result on immunoassays.38 Unfortunately,
routine GC-MS also does not distinguish between
the 2 isomers and requires chiral chromatography to differentiate
between the d- and l- forms.21
An added problem of amphetamine immunoassays is
their low sensitivity for detection of MDMA.87 Common
monoclonal amphetamine and methamphetamine immunoassays
(eg, EMIT, FPIA, and RIA) can detect MDMA
because of cross-reactivity; however, sensitivity for
MDMA is approximately 50% less than for amphetamine
and methamphetamine.88,89 High concentrations of MDMA
in the urine are needed to elicit positive results on amphetamine
immunoassays. However, specific tests have been
designed to incorporate 3 monoclonal antibodies specific
for amphetamine, methamphetamine, and MDMA, resulting
in greater sensitivity for detection of MDMA.87 These
tests should be considered if MDMA use is suspected