One Size Does Not Fit All

A Continued Discussion of False Positive Drug Testing

Teaching and disseminating medication information has been my mission for almost 44 years. I was very fortunate to have the opportunity to write a two-part series for the Pilot Protection Services on medications that may cause a false positive drug test (PPS June and August 2021). 

Over the past two years, I have received six questions on positive drug levels in patients and three questions that were aviation-related. I was contacted by healthcare providers and individuals who had read my articles in Dr. Google. I could find no logical reason for the positive findings. 

The most prevalent testing method is the urine drug test (UDT). An immunoassay screens the urine. Preliminary immunoassay positives are confirmed by GCMS (gas chromatography-mass spectrometry). Most urine tests will test for opiates, benzodiazepines, cocaine, THC, PCP, barbiturates, tramadol (non-opioid), fentanyl, and NMDA. A retrospective analysis of 8,825 deidentified patient drug results was studied. The drugs that were evaluated were amphetamine/methamphetamine/3,4-methylenedroxy-methamphetamine (MDMA), benzodiazepines (Valium-like medications), opioids (hydrocodone, hydromorphone, morphine, oxycodone), and tetrahydrocannabinol (THC). The false positive rate for amphetamines was approximately 14%, for opioids approximately 34% (excluding oxycodone), 100% for phencyclidine (PCP) and MDMA, and the false positive for THC was not reported (J anal Toxicol. 2016 Mar;40(2):97-107).

A study from the Quattrone Center for the Fair Administration of Justice, University of Pennsylvania, December 2023, evaluated drug field testing by police officers. The color-based presumptive testing was easy to use but had a high rate of false positives. The tests were improperly stored at higher temperatures than recommended, and there was an inability to read the colors, especially at night, and compare the test to the positive and negative color chart. These problems led to a high number of false positives and negatives. The study concluded that an estimated 33,000 arrests were made due to false positive results of the color-based presumptive tests.

The minimum annual random drug and alcohol testing rate by the Department of Transportation for 2024 is 25% for random drug tests and 10% for random alcohol testing. Pursuant to 14 CFR 120.109(b), the FAA Administrator’s decision to change the minimum annual random drug testing rate is based on the reported random drug test positive rate for the entire aviation industry. If the reported random drug test positive rate is less than 1.00%, the Administrator may continue the minimum random drug testing rate at 25%. In 2022, the random drug test positive rate was 0.786%. Therefore, the minimum random drug testing rate will remain at 25% for calendar year 2023.

Similarly, 14 CFR 120.217(c) requires the decision on the minimum annual random alcohol testing rate to be based on the random alcohol test violation rate. If the violation rate remains less than 0.50%, the Administrator may continue the minimum random alcohol testing rate at 10%. In 2022, the random alcohol test violation rate was 0.150%. Therefore, the minimum random alcohol testing rate will remain at 10% for the calendar year 2022 (Federal Register, a notice by the FAA on 11/17/23).

Let’s review my list of the most common medications that may cause a false positive test result for amphetamines. Bupropion extended-release (Wellbutrin XR Ò, XL Ò), labetalol (Trandate Ò), pseudoephedrine (Sudafed Ò), and ranitidine (Zantac Ò OTC). Bupropion extended-release is a norepinephrine and dopamine reuptake inhibitor. The indication for bupropion is for depression. Bupropion was added to the list of antidepressants (fluoxetine {Prozac Ò}, sertraline, {Zoloft Ò}, citalopram {Celexa Ò}, and escitalopram {Lexapro}, approved by the FAA with a special issuance. Labetalol is a beta-blocker indicated for hypertension. Pseudoephedrine is an over-the-counter decongestant that is also a medication utilized in combination with a non-sedating antihistamine, such as Loratadine/pseudoephedrine (Claritin-DÒ) for allergies and decongestion.

Serotonin reuptake inhibitors (SSRIs) are antidepressant medications that increase the amount of serotonin in the blood. Serotonin regulates mood. Patients with depression have low serotonin levels. Two SSRIs approved for use by the FAA that may cause false positive drug levels are fluoxetine (Prozac Ò) and sertraline (Zoloft (Prozac Ò).Fluoxetine has been reported to cause a false positive level of LSD and amphetamine. Sertraline may cause false positive drug levels for LSD and benzodiazepine.

THC (tetra-hydro-cannabinol) false positive drug levels have been reported when ibuprofen (Motrin Ò), naproxen sodium (Naprosyn Ò), and pantoprazole (Protonix Ò) are being administered. Ibuprofen and naproxen sodium are non-steroidal anti-inflammatories, and pantoprazole is a proton pump inhibitor that is indicated for gastroesophageal reflux disease. Verapamil (Calan Ò) is a calcium channel blocker that is prescribed for administration to patients with hypertension. Verapamil has been reported to cause a falsely elevated opioid level.

I am sharing three real case scenarios where a false positive drug test may have played a role. My disclaimer is that no names, where these experiences happened, and what companies were involved will be discussed. Case number one is an airline pilot randomly chosen for a drug test after a flight. The pilot tested positive for THC. This pilot has never smoked, eaten, or been around secondary marijuana smoke. He was prescribed naproxen sodium by his physician for knee pain. Case number two is a flight attendant who was randomly selected for drug testing and tested positive for THC. The flight attendant had a peptic ulcer and was prescribed pantoprazole (Protonix Ò). Case number three is a student pilot and a flight attendant who developed gastroesophageal reflux disease (GERD). She was prescribed pantoprazole for GERD. I spoke with the student pilot and recommended that the pantoprazole be changed to famotidine. Famotidine is a histamine blocker prescribed for patients with an ulcer or GERD. Famotidine will not cause a false positive THC level if the student pilot/flight attendant were to be randomly chosen for a drug test. Could two of the positive THC levels be false?

In my humble medication and research-based experience, our government agencies, HIMS physicians, and aviation lawyers need to take a very scientific look at false positive drug tests. There may be a small percentage of pilots who genuinely have not taken a forbidden drug. I have spent twenty-one years researching this phenomenon. There is a need to evaluate how we do drug testing, the reliability and specificity of the drug tests, and how many of the “false positive” drug tests are due to commonly prescribed medication interactions. The positive drug test impacts the careers of our aviation professionals. The recreational pilot is also affected if their employment requires randomized drug testing. To this small percentage of pilots, I say there may be a positive result from a false positive result. The phrase I continually express is, “Let’s be proactive and not reactive.” My mission is to keep you flying. Be well and fly safe.

Larry M. Diamond, PharmD, CFII
Larry Diamond has a Doctor of Pharmacy Degree and has been a pharmacist for 37 years. Larry’s pharmacy practice has been as a Clinical Pharmacy Specialist in Cardiology, Orthopedic Surgery Specialist and most recently Clinical Pharmacy Coordinator. He is a CFII, a pilot for 33 years and has been an AOPA member since 1984.

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