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.
Can amoxicillin or hydroxyzine give my son a false positive for cocaine?
Jun 09, 2022- False positives for cocaine on urine drug screens are extremely rare because the test looks for cocaine's specific metabolite and has very accurate detection with minimal cross-reactivity to other substances.
- Consuming products containing coca plant leaves or using topical cocaine for anesthesia are among the few reported substances that could potentially cause a false positive result.
- If you receive an unexpected positive result, a confirmatory test should be performed to rule out handling errors or sample problems.
A 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 coca plant leaves
- Topical cocaine for anesthesia
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 another article, which can be found here: What Cause False Positives On Drug Tests?
Below, we discuss various drug screening procedures.
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. It concluded that amoxicillin is unlikely to produce a false positive urine screen for cocaine.
As of the writing of this article, there is no sufficient evidence showing that any prescription drug will consistently cause a false-positive for cocaine.
References & sources
- Failure of amoxicillin to produce false-positive urine screens for cocaine metabolite — PubMed
- Urine Drug Screening: Practical Guide for Clinicians — Mayo Clinic Proceedings
Glossary — Terms in This Answer
- Metabolite
- A substance produced when the body breaks down and processes a drug.
- Benzoylecgonine
- The main breakdown product of cocaine that drug tests look for in urine.
- Cross-reactivity
- When a drug test reacts to a substance other than the one it is designed to detect.
- Topical
- Applied directly to the skin or surface of the body rather than taken internally.
- Confirmatory test
- A follow-up test performed to verify the accuracy of an initial positive result.
- Urine drug analysis
- A laboratory test that examines urine samples to detect the presence of drugs or their breakdown products.
- Concentration
- The amount of a substance present in a given volume of liquid.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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