PPI and False-positive THC Screen: False Positive Equal False Allegation

Abstract

Introduction: Proton pump inhibitor (PPI) is a class of medication frequently prescribed to treat, gastroesophageal reflux disease (GERD), and peptic ulcer disease. Yet, it is important to be mindful of the potential cause of false-positive urine cannabinoid screen in PPI users. We describe a case of a false-positive (FP) urine cannabinoid screen in a patient with pantoprazole usage. Case: A 43-year old male with a history of orthotopic liver transplant secondary to cirrhosis secondary to chronic hepatitis C, gastroesophageal reflux disease on proton pump inhibitor (PPI) presented to outpatient liver clinic for routine post transplant monitoring. Patient denied illicit drug abuse. On investigations, patient's urine drug screen (UDS) was positive for tetrahydrocannabinol (THC). A review of the patient's home medications (including divalproic acid, lasix, spironolactone, atorvastatin, and risperidone) and multiple discussions with the patient did not reveal a source for the positive urine cannabinoid screen. Patient was subsequently switched from pantoprazole to a histamine receptor blocker as there was high suspicion for false positive THC on UDS. Patient's repeat UDS done 2 weeks later showed negative reactivity to THC and has had a negative UDS since. Discussion: Urine drug screening for cannabinoids looks for metabolites of delta-9-tetrahydrocannabinol (THC). THC is the active ingredient in marijuana and can persist in the urine for multiple days to weeks depending on the chronicity of use. Very few substances such as Hemp-containing foods and passive inhalation of marijuana smoke have been implicated in positive THC screens. The pre-Food and Drug Administration approval data has labeled pantoprazole as a cause of false-positive urine screen for THC as no other drug in the class of PPI have been implicated with FP results. However, the exact mechanism of action leading to FP test result is unknown. It takes 4-5 days for Pantoprazole to be eliminated from the body. In our patient a repeat UDS was negative after the discontinuation of Pantoprazole. As many states are resisting the idea of legalizing marijuana, it is of great importance to be aware of the potential FP results in urine THC screening as this could compromise patients' eligibility to work or compete in athletic events.