title: Failure of amoxicillin to produce false-positive urine screens for cocaine metabolite.
abstract: Amoxicillin has been causally linked in the lay and medical literature to false-positive urine drug screens for cocaine metabolites. An exhaustive search of the peer-reviewed medical literature revealed no data to support this link. We hypothesized that amoxicillin does not cause false-positive urine drug screens for cocaine metabolites. To test this hypothesis, we examined the urine of 33 subjects administered a course of amoxicillin, subjecting the specimens to four common urine screening immunoassays. Thirty-one specimens were negative for the cocaine metabolite, benzoylecgonine (BE), by all four screening methods; two were positive for BE by all four screening methods. Both positive specimens were confirmed by gas chromatography-mass spectrometry (GC-MS) for the presence of BE at > 150 ng/mL. Three specimens that screened negative, but produced absorbance values that were intermediate between negative and positive controls, were submitted for GC-MS analysis; BE was detected in all three specimens at concentrations of 54, 94, and 119 ng/mL. Twenty-eight specimens produced screening results indistinguishable from negative controls. Within the limitations of the study design, we conclude that amoxicillin is unlikely to produce false-positive urine screens for cocaine metabolites.
authors.affiliation: Department of Community Health and Family Medicine, University of Florida Health Science Center, Jacksonville, Florida, USA.
authors.forename: Gary M
authors.initials: GM
authors.lastname: Reisfield
authors.forename: Judella
authors.initials: J
authors.lastname: Haddad
authors.forename: George R
authors.initials: GR
authors.lastname: Wilson
authors.forename: Laura M
authors.initials: LM
authors.lastname: Johannsen
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Voorhees
authors.forename: Chris W
authors.initials: CW
authors.lastname: Chronister
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Goldberger
authors.forename: James D
authors.initials: JD
authors.lastname: Peele
authors.forename: Roger L
authors.initials: RL
authors.lastname: Bertholf
mesh_terms: D000658:Amoxicillin / Q000493:pharmacokinetics*; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D003042:Cocaine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics* / Q000652:urine; D005189:False Positive Reactions; D006801:Humans; D015813:Substance Abuse Detection
chemical_list: D000900:Anti-Bacterial Agents; C005618:benzoylecgonine; D000658:Amoxicillin; D003042:Cocaine