Can Benzocaine Cause A False-Positive For Cocaine?

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 adultered 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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