title: Cross-Reactivity of Chloroquine and Hydroxychloroquine With DRI Amphetamine Immunoassay.
abstract: Chloroquine and hydroxychloroquine are medical drugs used to treat the chemoprophylaxis of malaria and a second-line anti-inflammatory drug.
  
  
  
  We performed a study of cross-reactivity of chloroquine and hydroxychloroquine in the DRI Amphetamine Assay inspired by a case report of a self-ingestion of chloroquine after a family dispute, that involved the following: (1) an in vitro study with control samples of healthy subjects, (2) an in vivo study with samples of patients with rheumatoid arthritis, and (3) an evaluation of the cross-reactivity of chloroquine and hydroxychloroquine in 3 additional immunoassays.
  
  
  
  In the case report, the Amphetamine DRI assay resulted positive both at 1000 ng/mL cutoff (1507 and 1137 ng/mL) and at 500 ng/mL cutoff (1178 and 642 ng/mL). Chloroquine urine levels were 103,900 and 100,900 ng/mL at 5 and 9 hours after ingestion. The results with control samples showed a positive cross-reactivity of chloroquine in the DRI Amphetamine Assay (approximately 0.74% and 0.89% at cutoff of 1000 and 500 ng/mL, respectively). Hydroxychloroquine did not cross-react with the DRI Amphetamine Assay up to 1,000,000 ng/mL. In patients treated with chloroquine or hydroxychloroquine, DRI Amphetamine did not produce false-positive results. The comparative assay study showed a positive cross-reactivity of chloroquine in the Emit II Plus Amphetamines Assay with control samples.
  
  
  
  Chloroquine can cause false-positive results in the DRI Amphetamine Assay when it is present at high concentrations. Hydroxychloroquine did not produce false-positive results neither in the DRI Amphetamine Assay nor in the others immunoassays evaluated.
authors.affiliation: *Clinical Toxicology Unit, Clinical Analysis Department, Hospital Universitari Son Espases, Research Institute of Health Sciences (IdISPa), Palma de Mallorca, Spain; †Research Institute of Health Sciences (IdISPa), Palma de Mallorca, Spain; ‡Division of Emergency, Department of Paediatrics, Hospital Universitari Son Espases, Palma de Mallorca, Spain; §Department of Rheumatology, Hospital Universitari Son Espases, Palma de Mallorca, Spain; ¶Clinical Analysis Department, Hospital Universitari Son Lla[Combining Grave Accent]tzer, Palma de Mallorca, Spain; ‖Clinical Analysis Department, Hospital Can Misses, Ibiza, Spain; **Division of Emergency Laboratory, Hospital Universitari de Bellvitge, Barcelona, Spain; and ††Reference Laboratory, Barcelona, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Gomila
authors.forename: Loreto
authors.initials: L
authors.lastname: Quesada
authors.forename: Victoria
authors.initials: V
authors.lastname: López-Corominas
authors.forename: Julia
authors.initials: J
authors.lastname: Fernández
authors.forename: Miguel Á
authors.initials: MÁ
authors.lastname: Servera
authors.forename: Laura
authors.initials: L
authors.lastname: Sahuquillo
authors.forename: Macarena
authors.initials: M
authors.lastname: Dastis
authors.forename: Albert
authors.initials: A
authors.lastname: Torrents
authors.forename: Bernardino
authors.initials: B
authors.lastname: Barceló
mesh_terms: D000293:Adolescent; D000661:Amphetamine / Q000627:therapeutic use / Q000652:urine*; D018501:Antirheumatic Agents / Q000652:urine; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000652:urine; D002738:Chloroquine / Q000627:therapeutic use / Q000652:urine*; D003429:Cross Reactions / Q000502:physiology; D005260:Female; D006801:Humans; D006886:Hydroxychloroquine / Q000627:therapeutic use / Q000652:urine*; D007118:Immunoassay / Q000379:methods; D015813:Substance Abuse Detection / Q000379:methods
chemical_list: D018501:Antirheumatic Agents; D006886:Hydroxychloroquine; D002738:Chloroquine; D000661:Amphetamine