Can Benzocaine Cause A False-Positive For Cocaine?
In our latest question and answer, the pharmacist discusses whether or not benzocaine can cause a false-positive drug test for cocaine.
Can topical benzocaine cause a false positive for cocaine in an oral swab?
Jul 06, 2022- Benzocaine is a topical anesthetic used in over-the-counter products like Orajel and is structurally different from cocaine despite the similar spelling. Urine drug tests for cocaine look for a specific metabolite called benzoylecgonine, which benzocaine does not produce and therefore cannot cause a false-positive result. False positives for cocaine are extremely unlikely from other drugs or substances, and benzocaine is not known to cross-react with cocaine screening tests.
Thanks for reaching out to us! We've answered a number of questions regarding what drugs or substances could potentially cause false-positive results on urine drug screenings, so we're more than happy to help you with this.
Benzocaine is a topical anesthetic and a common ingredient in several over-the-counter products, such as Orajel and Anbesol. It is structurally related to para-aminobenzoic acid (PABA) and works by blocking nerve conduction. Cocaine on the other hand, is a central nervous stimulant. Interestingly enough, cocaine does have medicinal applications as a topical anesthetic as well but works via a different mechanism than benzocaine.
Although benzocaine and cocaine have a similar spelling, they aren't very closely related, structurally, and their metabolites are not similar enough that they would cause a false-positive result on a urine drug test for each other.
Benzocaine - Cocaine False-Positive?
Several studies have reported pretty definitively that it is extremely unlikely that other drugs or substances (including benzocaine) will cause a false-positive urine drug screening result for cocaine.
One such study, the highly cited 'Urine Drug Screening: Practical Guide for Clinicians' reports the following regarding cocaine and urine drug tests:
Urine drug screens used to evaluate cocaine ingestion assess the presence or absence of cocaine's main metabolite, benzoylecgonine. Cross-reactivity between this screen and substances other than cocaine are nearly nonexistent.
False positives for cocaine have been reported with substances derived from coca plant leaves, or with substances that normally do not contain cocaine, but are adulterated with it. Other than that, the chance of a false-positive occurring with anything else is uncommon.
So, to answer your question specifically regarding whether or not a benzocaine swab could cause a positive result for cocaine, no, this wouldn't be considered a possibility. Urine drug tests look for the cocaine metabolite 'benzoylecgonine', which is quite different than benzocaine and not known to have cross-reactivity with benzocaine.
This answer applies to all of the 'caine' topical anesthetics, including procaine and lidocaine as well. These are not known to cause false positives for cocaine on urine drug tests either.
Final Words
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References & sources
- Cocaine Monograph — PubChem
- Benzocaine Monograph — PubChem
- Urine Drug Screening: Practical Guide for Clinicians — Mayo Clinic Proceedings
- Drug Testing And 'Caine' Drugs — Chemical & Engineering News
Glossary — Terms in This Answer
- Topical anesthetic
- A medication applied to the surface of the skin or mucous membranes to numb a specific area.
- Para-aminobenzoic acid (PABA)
- A chemical compound that is structurally similar to benzocaine and found in some over-the-counter products.
- Nerve conduction
- The process by which nerves transmit electrical signals that carry pain and other sensations.
- Central nervous stimulant
- A drug that increases activity and alertness in the brain and central nervous system.
- Metabolites
- Chemical substances produced when the body breaks down and processes drugs or other compounds.
- False-positive result
- An incorrect test result that indicates the presence of a substance when it is not actually present.
- Benzoylecgonine
- The main metabolite of cocaine that urine drug tests specifically look for to detect cocaine use.
- Cross-reactivity
- When a drug test reacts to a substance other than the one it is designed to detect.
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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