Medications That Can Cause A False Positive For Methamphetamine

In our latest question and answer, the pharmacist discusses what over the counter and prescription drugs can cause false positives for methamphetamine on drug tests.

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Mar 31, 2018

angie asked

What over the counter and prescription medicine show a false positive on methamphetamine tests?

Answer

Methamphetamine TestThere are many different over the counter and prescription medications that have been reported to cause false positives for methamphetamine on a drug test.

All of the following medications have documented cases of causing a false positive for either amphetamine or methamphetamine:

  • Amantadine
  • Dimetapp (Brompheniramine)
  • Wellbutrin (Bupropion)
  • Chlorpromazine
  • Chloroquine
  • Desipramine
  • Doxepin
  • Labetalol
  • Ritalin (Methylphenidate)
  • Sudafed PE (Phenylephrine)
  • Promethazine
  • Sudafed (Pseudoephedrine)
  • Zantac (Ranitidine)
  • Selegiline
  • Thioridazine
  • Trazodone
  • Trimethobenzamide
  • Effexor (Venlafaxine)
  • Vicks inhaler

Sources: Study One, Study Two, Study Three

Methamphetamine False Positives

False positives on drug tests are unfortunately fairly common. The main issue is the tests themselves.

Most drug tests are simple, urine based immunoassay tests. Common ones include the EIA (Enzyme Linked Immunoassay) test and the CEDIA (Closed Enzyme Donor Immunoassay) test. They both use similar principles. They work by utilizing antibodies to react to specific drug compounds. When a specified drug is present in a test urine sample, an antibody binds to it and produces a reaction. When a reaction occurs, it is classified as 'positive' result.

Immunoassay tests have a significant problem with 'cross-reactivity'. Often times, drugs that are NOT being tested for can react with the wrong antibody (i.e. 'cross react'), resulting in a 'false positive'. 

If you get a false positive for methamphetamine, you could simply ask to retake the test if that is allowed.

Additionally, you can ask to take a more accurate and conclusive test that can detect drug compounds in a specific manner such as gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). These tests do not use antibodies and can accurately determine the exact molecule being looked for.

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