The abbreviation “AMP” on a drug test refers to amphetaminesa class of powerful central nervous system stimulants. Amphetamine testing is a standard component of most panel screensroutinely used for pre-employmentlegaland medical monitoring. While the primary goal is to detect illicit substancesthe test also screens for legally prescribed medications in this chemical category. The initial screening is highly sensitive but not entirely specificmeaning a positive result does not automatically confirm illegal drug use. Accurate interpretation requires understanding the difference between the intended targets and other substances that can interfere with the test.
The Core Targets of the Amphetamine Panel
The amphetamine panel detects compounds sharing the phenethylamine structure. This includes the parent drugamphetamineoften prescribed for conditions like ADHD and narcolepsy; medications like Adderall will trigger a positive result. Methamphetaminea more potent compound known as crystal methis another primary target. The body metabolizes methamphetamine into amphetamineso a positive result for both often indicates methamphetamine use. The panel also detects designer drugs like 3,4-methylenedioxymethamphetamine (MDMA)or Ecstasyand its metaboliteMDA.
How Drug Screening and Confirmation Tests Work
Drug testing follows a two-step process to ensure accuracy. The initial screen uses an immunoassay (IA) techniquewhich is fast and inexpensive. This method utilizes antibodies designed to bind to the drug or its metabolites above a predetermined concentration threshold.
The immunoassay is highly sensitive to minimize false negativesbut this comes at the cost of specificity. Antibodies can cross-react with other compounds structurally similar to amphetamines. A positive immunoassay result is considered a presumptive positivenecessitating a secondmore definitive step.
The confirmatory test uses sophisticated technologyusually Gas Chromatography-Mass Spectrometry (GC/MS) or Liquid Chromatography-Mass Spectrometry (LC-MS/MS). This technique separates the sample into its chemical componentsidentifying the exact molecular fingerprint of any substance present. These methods are the gold standard because they are highly specific and accurately distinguish amphetamine from chemically similar compoundsruling out false positives.
Common Medications That Cause False Positives
A significant number of legally available medications and over-the-counter products can result in a presumptive positive for amphetamines on the initial immunoassay screen. This occurs due to chemical cross-reactivitywhere the antibodies in the test mistake a non-amphetamine molecule for the target drug. Several common medications are structurally similar to amphetamines and frequently trigger false positives:
- Antidepressants like bupropion (used for depression and smoking cessation) and sertraline.
- Over-the-counter cold remedies containing decongestants such as pseudoephedrine and ephedrine.
- The cough suppressant dextromethorphan and certain antihistamines like brompheniramine.
- The weight-loss stimulant phentermine.
- Certain beta-blockers (e.g.labetalol) and the antacid ranitidine.
If a person is taking any of these medicationsthe initial screening result must be viewed with caution until a confirmation test is performed.
Necessary Steps Following a Positive Screening
If an initial immunoassay screen returns a presumptive positive result for amphetaminesthe process mandates the involvement of a licensed physician known as a Medical Review Officer (MRO). The MRO acts as an independent gatekeeperdetermining if a legitimate medical explanation exists for the non-negative test result. The MRO initiates confidential contact with the individualtypically making at least three attempts within a 24-hour period.
During this interviewthe MRO asks the donor to provide documentationsuch as valid prescriptions or medical recordsto explain the substance’s presence. If the donor confirms using a medication known to cause cross-reactivitythe MRO orders the confirmatory GC/MS or LC-MS/MS testing. If the confirmatory test verifies the substance is a legitimately taken prescription medicationthe MRO reports the final result to the employer as negative. This crucial step protects the individualensuring that legal and prescribed medication use is not misinterpreted as illicit drug use.