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Seven Things To Know When You Receive A Notice Of Investigation From The Department Of Health

Medications and Other Substances that Mimic Prohibited Drugs on Urinalysis Drug Tests: Cocaine and Imposter Substances (Part 2 of Series)

By George F. Indest III, J.D., M.P.A., LL.M., Board Certified by The Florida Bar in Health Law, and Hartley Brooks, Law Clerk, The Health Law Firm

When representing nurses and other license health professionals, our firm often encounters issues regarding positive drug tests that employers request.  These clients include nurses, pharmacists, dental professional, mental health counselors, therapists, etc.  Job seekers should be aware that employers, particularly large companies and government organizations, may require drug tests as part of the hiring process.

These issues are particularly relevant when a health professional has applied to a hospital, a medical organization, or a placement agency for work in a hospital and is required to submit to a pre-employment drug test.  The client often contends that a positive result is a false positive and that some other substance must be responsible for it.

A positive result for any drug for which you do not have a valid prescription from a physician, including marijuana, can have severe and far-reaching consequences.  It could result in being eliminated from consideration for a new job or termination from a current position.  It can also result in a complaint against your professional license, which could lead to its suspension or revocation.  This could be devastating to your career and your future job prospects.  Our firm is routinely called on to defend health professionals in such situations.

Remember to read Part 1 and Part 3 of this blog series! Part 1 deals with substances that may cause a false positive for amphetamines. Part 3 Marijuana and THC Imposter Substances.

Routine Drug Testing.

Most routine drug tests are “five panel” urinalysis drug tests to detect marijuana, cocaine, opiates, amphetamines, and phencyclidine. Sometimes a “ten panel” or “21 panel” test is used, depending on the employer. These drug tests are most often immunoassay (IA) tests that screen for the common classes of drugs mentioned above.  An IA drug test is typically used to evaluate the use of illegal substances and not prescribed medications or the abuse of prescribed medications.  These drug tests will test for the drugs and their metabolites to assess usage.

A false positive is when a drug test detects a substance or metabolite that is not actually one that is from the prohibited drug.  Instead, the test is detects an imposter substance acting like the one it is looking to detect.  Another urinalysis drug test used is a gas chromatography-mass spectrometry (GC/MS) test.  This test is considered the “gold standard” of drug tests.  But, due to its complexity and its cost, it is typically used only to confirm positive IA test results.

Cocaine False Positives.

Cocaine is known to have one major substance that will yield false positives in drug screens:  coca leaf and coca leaf tea.  Coca leaf is the source of cocaine, which is a Schedule II narcotic in the United States.  Due to cocaine’s being an illegal substance, coca leaf and coca leaf tea are also illegal in the United States, both for brewing as a tea and for chewing.

Consumption of coca tea and the chewing of its leaves is common in South America, especially where coca leaf is grown in Peru, Bolivia, and Columbia. While coca leaf is illegal in the United States, it is still easily accessible for purchase over the Internet and in other countries.  Urine analysis of subjects who ingested coca tea indicated that cocaine and two of its metabolites, benzoylecgonine (BE) and ecgonine methyl ester, were present in varying quantities.

Examples of False Positives from Coca Leaf Tea.

We have had several clients who screened positive for cocaine on employer ordered drug tests, because of their earlier ingestion of coca leaf tea.

On one case a nurse was visiting his grandmother who was from South America.  The grandmother had container of tea bags that looked like regular, commercial tea sold in the United States.  He brewed a cup of tea and drank it, not knowing that it was coca leaf tea.

The next day, he had an employer ordered drug test.  His drug test was positive for cocaine. Backtracking to try to determine the source, we discovered the package that the coca leaf tea bags were in.  They were clearly labeled “coca leaf” but were not labeled as containing cocaine, being illegal or with any other warnings.  The grandmother had brought these back with her on her last trip to South America.

In another case, someone had given a pharmacist a gift basket containing crackers, honey, teas and other different food products.  A box of various different teas was included in the gift basket.

The pharmacist sampled the different teas at different times.  However, when her employer ordered a drug test, it came back with a positive for cocaine.  The pharmacist was suspended.

Backtracking to try to find the reason for the positive drug test, we located the gift basket’s label and contents and the tea box, showing that the coca leaf tea was included.  The gift basket had been assembled in a foreign country and shipped to the pharmacist from outside the United States.

Amoxicillin and False Positives for Cocaine.

Amoxicillin is also rumored to be a potential source for a cocaine false positive for a urinalysis drug screening.  However, a study reporting in the Journal of Analytical Toxicology in 2008 seemed to find otherwise.  The results from the study found amoxicillin to be an unlikely imposter substance, although the scientific validity of the study might be questioned.

The study tested 33 urine samples from subjects who had been administered a course of amoxicillin.  31 urine samples tested negative; however, two tested positive for BE, a cocaine metabolite.  The amount in the two samples that tested positive for the cocaine metabolite was less than 150 nanograms per milligram, the federal cut-off for cocaine.  Therefore, the study concluded that amoxicillin is unlikely to cause a false positive urinalysis drug test for cocaine.  Click here to read the full study.

I personally take issue with this conclusion.  A big red flag here, however, is that this study does show that two out of the 33 samples were, in fact, positive for a cocaine metabolite, or at least its imposter.  That’s six percent (6%) or the universe tested.  With the millions of people who take amoxicillin every day, that equates to a pretty large number.  If one million people each day are on amoxicillin, then this means 60,000 of them could test positive for cocaine on a urinalysis test.

The Centers for Disease Control (CDC) states that in 2019, 54.1 million prescriptions for amoxicillin were written in the U.S.  If the same percentage were applied to this group, then 3,346,000 people would test positive for cocaine.

Furthermore, the drug screening tests used by many employers and especially those used by state sponsored provider health programs or peer assistance programs such as the Florida Intervention Project for Nurses (IPN) and the Florida Professional Resources Network (PRN) often use a much lower cut-off level than the federal level.

One must also question whether the study conducted used statistically significant samples and whether it would be considered scientifically valid or not. From the small numbers, it probably isn’t. However, it did produce some evidence that amoxicillin can cause a false positive for cocaine.

Other Discussions in Future Blogs.

Remember to read Part 1 and Part 3 of this blog series! Part 1 deals with substances that may cause a false positive for amphetamines. Part 3 Marijuana and THC Imposter Substances.


Algren M.D, Adam D., Micheal R. Christian M.D.. “Buyer Beware: Pitfalls in Toxicology Laboratory Testing.” Missouri Medicine: The Journal of the Missouri State Medical Association. (May 2015). 

“Can I Bring Coca Leaves into the United States?” U.S. Customs and Border Protection. (21 June 2023).,in%20Bolivia%2C%20Peru%20and%20Colombia.

Centers for Disease Control and Prevention. Outpatient antibiotic prescriptions–United States, 2019. (accessed June 30, 2023)

“Cutoff levels for drugs and drug metabolites.” 10 Code of Federal Regulations Section 26.133. (accessed 6/30/2023, last amended 6/26/2023)

Jenkins, Amanda J., Teobaldo Llosa, Ivan Montoya, and Edward J. Cone. “Identification and Quantitation of Alkaloids in Coca Tea.” Forensic Science International. (9 February 1996).,urine%20drug%20test%20for%20cocaine.

Olsson, Reagan. “What Medications Can Cause False Positives on Drug Tests?” Banner Health. (7 Janurary 2023).

Raouf PharmD., Mena, Jeffrey J. Bettinger PharmD, and Jeffrey Fudin PharmD. “A Practical Guide to Urine Drug Monitoring.” Federal Practitioner. (2018).

Reisfield, G. M., Haddad, Johannsen, Voorhees, Chronister, Goldberger, Peele, & Bertholf. “Failure of amoxicillin to produce false-positive urine screens for cocaine metabolite.” Journal of analytical toxicology, 32(4), 315–318. (2008).

Contact Experienced Health Law Attorneys in Matters Involving PRN or IPN.

The Health Law Firm’s attorneys routinely represent nurses, pharmacists, counselors, physicians, dentists, and other health professionals in matters involving allegations of impairment, drug diversion, and drug abuse, and referrals to the Intervention Project for Nurses (IPN), the Professional Resource Network (PRN), physician health programs, and peer assistance program.

About the Authors:  George F. Indest III, J.D., M.P.A., LL.M., is Board Certified by The Florida Bar in Health Law. He is the President and Managing Partner of The Health Law Firm, which has a national practice. Its main office is in the Orlando, Florida, area. The Health Law Firm, 1101 Douglas Avenue, Suite 1000, Altamonte Springs, FL 32714, Phone: (407) 331-6620; Toll-Free (888) 331-6620

Hartley Brooks is a law clerk at The Health Law Firm. She is preparing to attend law school.

Current Open Positions with The Health Law Firm.  The Health Law Firm always seeks qualified individuals interested in health law.  Its main office is in the Orlando, Florida, area.  If you are a current member of The Florida Bar or a qualified professional who is interested, please forward a cover letter and resume to:  [email protected] or fax them to (407) 331-3030.

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