What Can Cause A False Positive For Cocaine?

In our latest question and answer, the pharmacist discusses what other medications can cause a false positive for cocaine.

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May 31, 2018

kmp asked

Can amoxicillin or hydroxyzine give my son a false positive for cocaine?

Answer

Drug TestA variety of medications can cause a false positive result on a drug screen, but the occurrence of a false positive result for cocaine is very rare. False positives are far more common for other medications such as amphetamines and opioids.

Cocaine False Positives

Most urine drug screens utilized to test for cocaine ingestion look for cocaine's main metabolite, benzoylecgonine.

One of the most utilized references regarding drug screenings, Urine Drug Screening: Practical Guide for Clinicians, reports that false-positives for cocaine are exceedingly uncommon. Per the guide:

"Cross-reactivity between this screen [urine] and substances other than cocaine are nearly nonexistent. Urine screens for cocaine are very accurate in detecting recent cocaine ingestion"

Nevertheless, there are a few reported substances that can cause false positives for cocaine. These include:

  • Consumption of natural products containing with coca plant leaves
  • Topical cocaine for anaethesia

If you have received an unexpected positive result, it is recommended to perform a confirmatory test to make sure there was no handling or sample error. We wrote extensively about "false-positives" in other article, which can be found here: What Cause False Positives On Drug Tests?

Below, we discuss various drug screening procedures that will described below.

Urine Drug Analysis For Cocaine

Urine drug analysis is commonly used as the standard for employment screenings as it is quick and painless. This procedure requires individuals to urinate into a medical cup. The test requires at least 30 mL of urine and will test for recent or new drug use. To be considered a positive result for cocaine, the concentration of cocaine levels must be 300ng/ml or higher.

Though it is commonly thought that amoxicillin could cause a false positive result, one study found that the opposite is true. This study concludes that amoxicillin is unlikely to produce a false positive urine screen for cocaine.

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