Last updated : July 7, 2025
The Department of Transportation (DOT) doesn’t sway from demanding compliance from employers who hire a safety-sensitive workforce. There are many rules and regulations to adhere to if employers want to remain in compliance. The DOT drug test was incorporated into the mandates to ensure that drivers aren’t impaired while on the road. Its design, of course, was to keep the public as safe as possible while traveling the nation’s highways and byways.
You would assume that someone operating a commercial vehicle would never consider being impaired by drug use when behind the wheel. However, the Federal Motor Carrier Safety Administration (FMCSA) Drug and Alcohol Clearinghouse (DACH) reported that since the database went live in January 2020, over 227,000 commercial motor vehicle drivers have failed a drug test and were removed from service.
It’s nearly impossible for a drug test result to show an inaccurate result. Drug testing technology has become very advanced over the years. Moreover, the sensitivity of laboratory equipment continues to become more and more precise. Still, some drivers who test positive for drugs dispute the results of their DOT drug test.
The DOT gives an employee who tests positive for drug use to dispute the result within 72 hours of learning of the positive result. When a test result is disputed, a second, more in-depth, test is performed. The employee doesn’t provide a specimen for the second test though. It’s done on the original specimen.
How is that possible?
The DOT’s drug testing protocol stipulates that each urine specimen be divided into two separate collection cups. Initially, testing is completed on one of the specimens. The second is stored. If the employee notifies the Medical Review Officer (MRO), either verbally or in writing, that they don’t agree with the test result, then the second specimen is sent out to a different SAMHSA-certified laboratory for further testing.
Noted in the DOT’s protocol as the split specimen test, the procedure stipulates that the test won’t be performed if the first test proves invalid.
If the “backup” specimen is returned with a positive result, the MRO contacts the employee. It could be that there is a valid reason for the positive test result. For instance, some medications are known to cause a false positive drug test result. If the employee can present evidence that they have been taking prescription medications or over-the-counter medications that are known to cause positive test results, the MRO will confirm the same to the employers and anyone else who requires the information.
We should note here that the DOT recently released a final ruling regarding oral fluid tests. They are allowed as an alternative to the urine drug test. Protocol for using the oral fluid test mandates a split sample test be administered using mouth swabs as well. However, employers can’t begin using the test until two laboratories have been approved by SAMHSA to perform testing. We’ll keep you posted.
Some drugs trigger false positive results
It is extremely rare, but possible that the DOT drug test result could be inaccurate due to a laboratory error. It’s more likely that some other form of medication triggered a false positive result on the urine test.
Some medications known to affect DOT drug testing are:
- Dextromethorphan—found in Robitussin and Delsym—can trigger a PCP result
- Diphenhydramine—found in Benadryl—can trigger an opioid result
- Pseudoephedrine—found in certain decongestants—can trigger and amphetamine or methamphetamine result
- Phentermine—a weight loss medication—can trigger an amphetamine result
- Quetiapine—used to treat certain mental health conditions—can trigger an opioid result
- Proton Pump Inhibitors—used to treat gastroesophageal reflux disease (GERD) and heartburn—can trigger a THC result
- Promethazine—used to relieve nausea and vomiting—can trigger both amphetamine and methamphetamine results
- NSAID’s—Ibuprofen, and naproxen, both used to treat fever, inflammation, and pain—can trigger both THC and barbiturate results
- Quinolone Antibiotics—used to treat bacterial infections—can trigger either amphetamine, methamphetamine, or opioid results
- Venlafaxine and Desvenlafaxine—antidepressant medications, such as Effexor XR and Pristiq—can trigger a PCP result
- Sertraline—brand name Zoloft—can trigger both Benzodiazepine and LSD results
- Trazodone—an older antidepressant that’s not used often—can trigger amphetamine and methamphetamine results
- Bupropion—brand name Wellbutrin—can trigger amphetamine and methamphetamine results
Positive proof
It would be highly illogical for someone to dispute a DOT drug test result if they knew they recently used drugs. So, when someone disputes the result of a DOT drug test, one of the medications listed above could have triggered the result. False positive results on urine drug tests are rare, but possible, even if the person never ingested the drug.
The MRO is responsible for determining if that’s the cause and alerting all necessary parties—such as the employer and the FCMSA Drug and Alcohol Clearing House. When the employee’s record is cleared, they are immediately returned to duty.
