‘Breaking Bad’ on a Routine Urine Drug Screen: The case of an innocent drug-positive

Post Contribution by Dr. Lena Palaniyappan

Often we request urine drug screening when we suspect possible drug use, but cannot trust what the patient says. What if this test declares a non-user as being positive?

Who will you believe in – the test or the tested? 

One of my patient who was on treatment for depression for more than 3 years, landed in a new job after much struggle. I was genuinely pleased for him. He was undergoing routine paperwork before taking up the job in the next few days. Then, out of the blue, he rang my office in despair.

His new employers asked for a random urine drug test, and he turned positive for amphetamine and LSD (Lysergic Acid Diethylamide). Yikes!

I knew him quite well. He was not a user. He was devastated.

We set out to find the reasons for this false-positivity. Could it be contamination? Or a genuine lab mix-up?

It turned out that the antidepressant that he was on, desipramine, can cause notorious false positive results for both amphetamine and LSD. Holy Moly!

We know how important urine drug screen testings are for our clinical practice, but these are also used in educational, employment and legal settings. Hence, it is very important for clinicians to interpret these test results and have knowledge of false positive results. The misinterpretation of results can have negative consequences for the individuals being tested.

Let’s answer this question first:

Which of the following non-psychotropic medications can have false-positive results for amphetamine?

Answer: All of the above

Learn all you need to know about potential false positive drug screen in our course chapter.

In this chapter we talk about:

  1. False positive for cannabinoids. 
  2. False positive for opioids 
  3. False positive for benzodiazepines. 
  4. False positive for phencyclidine 
  5. False positive for tricyclic antidepressants. 
  6. False positive for amphetamine. 
  7. False positive for methadone. 
  8. False positive for LSD (lysergic acid diethylamide). 
  9. False positive for barbiturates.


  • Saitman A, Park HD, Fitzgerald RL. False-positive interferences of common urine drug screen immunoassays: a review. J Anal Toxicol. 2014;38(7):387-396. doi:10.1093/jat/bku075



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