Protonix (pantoprazole) can cause a false positive urine screening test for THC

March 5, 2015, 11:57 pm

protonix★★★½☆

13-Year-Old Girl With Recurrent, Episodic, Persistent Vomiting: Out of the Pot and Into the Fire. Felton D et al. Pediatrics 2015 Mar 2 [Epub ahead of print]

Abstract

The package insert for Protonix (pantoprazole) states:

There have been reports of false positive urine screen tests for tetrahydrocannabinol (THC) in patients receiving protein pump inhibitors.

The source of these reports have not been clear, and no cases have previously been reported in the literature. This paper describes a 13-year-old girl who presented to hospital with an episode of recurrent cyclic vomiting syndrome, who was diagnosed with cannabinoid hyperemesis syndrome when a urine screening test was positive for THC. After a confirmatory gas chromatography-mass spectrometry test was negative for cannabinoids, the consulting toxicologist pointed out that the patient had received IV pantoprazole several hours before the urine specimen was obtained, and that the protein pump inhibitor was possibly responsible for the false positive test.

Although many clinicians are not aware of this effect, it is often mentioned in online drug discussion groups. This is the first case reported in the medical literature and — as the authors note — it is not clear if other protein pump inhibitors can also cause false positive tests for THC. The mechanism is not known.

H/T Nadia Awad (@Nadia_EMPharmD)

5 Comments:

  1. forensictoxguy Says:

    Yes, in the analytical toxicology world, pantoprazole is well-known to cause a false positive immunoassay result for cannabinoids. I have also seen omeprazole/esomeprazole do the same thing.

  2. Leon Says:

    forensictoxguy:

    Thanks for the additional information. Are you aware of anything in the medical literature describing this, aside from this paper by Felton et al?

  3. Andrew Says:

    Well, let’s have a look at Pfizer’s package insert for Protonix(http://labeling.pfizer.com/ShowLabeling.aspx?id=135):

    “7.5 False Positive Urine Tests for THC – There have been reports of false positive urine screening tests for tetrahydrocannabinol (THC) in patients receiving proton pump inhibitors. An alternative confirmatory method should be considered to verify positive results”

    I have never been able to find any study or paper on this (just articles that seem to treat this false-positive, and many others, as established fact)

    Even baby shampoo seems to provide false positives for THC: http://www.ncbi.nlm.nih.gov/pubmed/22465236

  4. Dan P Says:

    Another reason for Poison Control staff to refer callers to their institution’s laboratory directors or have the toxicology results confirmed using a different method.

  5. Leon Says:

    Andrew:

    I was also not able to find a previous published case reporting this. It appears that this phenomenon was reported to the manufacturer but never appeared in the literature. That is the major reason I found the case report by Felton et al so interesting.

    Dan P:

    I completely agree that is crucial to confirm positive urine screens when the real answer is important. In this case, there were Child Services issues that came into play until the confirmatory test came back negative.