Quinolones and false-positive urine screening for opiates by immunoassay technology

JAMA. 2001 Dec 26;286(24):3115-9. doi: 10.1001/jama.286.24.3115.


Context: Millions of assays are performed each year to monitor for substance abuse in various settings. When common medications cross-react with frequently used testing assays, false-positive results can lead to invalid conclusions.

Objective: To evaluate cross-reactivity of quinolone antimicrobials in common opiate screening assays and to assess the in vivo implications of this phenomenon.

Design, setting, and participants: The reactivity of 13 quinolones (levofloxacin, ofloxacin, pefloxacin, enoxacin, moxifloxacin, gatifloxacin, trovafloxacin, sparfloxacin, lomefloxacin, ciprofloxacin, clinafloxacin, norfloxacin, and nalidixic acid) was tested in 5 commercial opiate screening assays from September 1998 to March 1999. In 6 healthy volunteers, we confirmed the cross-reactivity of levofloxacin or ofloxacin with these opiate screening assays.

Main outcome measure: Opiate assay activity (threshold for positive result, 300 ng/mL of morphine).

Results: Nine of the quinolones caused assay results above the threshold for a positive result in at least 1 of the assays. Four of the assay systems caused false-positive results for at least 1 quinolone. Eleven of the 13 compounds caused some opiate activity by at least 1 assay system. At least 1 compound caused opiate assay activity in all 5 assay systems. Levofloxacin, oflaxacin, and perfloxacin were most likely to lead to a false-positive opiate result. Positive results were obtained in urine from all 6 volunteers.

Conclusion: Greater attention to the cross-reactivity of quinolones with immunoassays for opiates is needed to minimize the potential for invalid test interpretation.

MeSH terms

  • 4-Quinolones
  • Anti-Infective Agents / metabolism*
  • Cross Reactions
  • False Positive Reactions
  • Humans
  • Immunoassay
  • Opioid-Related Disorders / diagnosis*
  • Opioid-Related Disorders / urine
  • Substance Abuse Detection*
  • Urinalysis


  • 4-Quinolones
  • Anti-Infective Agents