What Medications Could Give a Positive Amphetamine Reading

January/Feb 2015

Drug Monitoring and Imitation Positives

Urine drug screenings are useful diagnostic tests. In chronic pain direction, drug testing can assess the advisable intake of drugs, help with the diagnosis of substance abuse, and improve drug management.^aneScreening for illicit drugs or misused medications can be useful in assessing and monitoring patients with chronic pain. It is of import to consider the potential for faux positive results (ie, incorrect indications) when the results of urine drug screenings are interpreted. Annotation that false negatives can also occur, when a drug is present in the patient's system simply not showing up on the screening results.

Drugs That Can Cause False Positives

Several common medications can lead to a false positive on a drug screen, including but not express to: brompheniramine, bupropion, chlorpromazine, clomipramine, dextromethorphan, diphenhydramine, doxylamine, ibuprofen, naproxen, promethazine, quetiapine, quinolones (ofloxacin and gatifloxacin), ranitidine, sertraline, thioridazine, trazodone, venlafaxine, verapamil.

Amphetamine (more on this below) and methamphetamine are the most usually reported false positive. More complex drugs tin also show up incorrectly on drug screen results: methadone, opioids, phencyclidine, barbiturates, cannabinoids (run across as well, a sample case report on marijuana simulated positives and an inquire the expert QA on imitation-positve marijuana results), as well every bit benzodiazepines were likewise reported in patients taking usually used medications
.

An OTC nasal inhaler can cause a false positive too.

How Drug Tests Are Washed

Urine specimens are typically preferred although oral flued may be used likewise. There are two main types of urine monitoring tests: presumptive and definitive.

Presumptive drug monitoring identifies possible use or not-use of drugs or drug classes and includes lab-based immunoassay and point-of-care methods. Results are expressed as negative or presumptive-positive, and cannot distinguish true-positive from false-positive results.

Definitive drug monitoring, which tin can be more than costly, identifies specific drugs and metabolites, and can confirm presumptive results or rule out presumptive false-positives. Come across strategies for a ii-footstep approach and more than specific details on what these tests can and cannot testify in our Clinician Guide on Drug Monitoring.

False Positive for Amphetamines

Urine screenings for amphetamines commonly involve the use of immunoassays. Multiple immunoassays are bachelor, and they all share similar bones methodology. In these tests, a sample of urine or actual fluid is added to a solution containing antibodies or immunoglobulins, which demark to targeted analytes. Past interacting with specific structures, the immunoglobulins signal the presence of certain drugs.² Immunoassays frequently are used in initial urine drug screenings because they provide rapid results, cost relatively little, and are commercially available. However, simulated positives are possible and must be considered when interpreting results.

Immunoassays often lack the specificity to target individual drugs and typically screen for structurally related compounds. Immunoassays for amphetamines can observe several related chemicals, including methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,iv-methylenedioxymethamphetamine (MDMA), and methylenedioxyethylamphetamine (MDEA), that share a common structure that includes a phenyl ring and an amino group continued past a two-carbon side chain.³ However, these structural elements also can be constitute in other not-amphetamine drugs every bit shown in Figure one (below), and this may issue in false positive urine screenings.^4-7

For instance, the commonly used decongestants pseudoephedrine and phenylephrine share similar structural characteristics with amphetamines, and cantankerous-reactivity with screenings has been documented.^2,viii A instance report linked the use of intravenous (4) phenylephrine to a false positive amphetamine screening.^ix Upon admission, the patient's routine immunoassay for amphetamines showed a negative issue, but after 3 days, a repeat analysis was positive for amphetamine. A confirmatory test was ordered and identified Iv phenylephrine as a likely cause of the fake positive.

Some other drug that has been associated with false positive results for amphetamine is ane,three dimethylamylamine (DMAA). DMAA has sympathomimetic activity and is an ingredient in some dietary and weight-loss supplements. A case study linked a false positive amphetamine screening to use of the weight-loss supplement Oxyelite Pro.¹⁰ In addition, a review of drug screenings conducted by the Department of Defense showed that DMAA was associated in 124 cases out of 134 fake-positive amphetamine samples. Positive amphetamine screens from 2 initial separate immunoassays were adamant to be false positive in confirmatory testing.¹¹ Identifying pseudoephedrine, phenylephrine, and DMAA equally possible causes of imitation positives is especially problematic because they are available over-the-counter, causing some patients to be unaware of their intake.

In addition to weight-loss supplements, bupropion, which is used as an antidepressant and smoking abeyance assistance, also is structurally similar to amphetamine and has been associated with false positive screenings. A retrospective chart review of x,011 urine drug screens found that of 362 initial positive amphetamine tests, 128 (35%) were false positives. In 53 of these false positives (41%), utilize of bupropion was documented.¹² A case report also described a patient taking 300 mg of bupropion daily and testing falsely positive for amphetamines. A reference test, which added bupropion to drug-complimentary urine, showed that the cross-reactivity of bupropion with the amphetamine immunoassay ranged from 3% to 17%, depending on concentration.¹³

Other drugs tin undergo metabolism and cause false positive results. Meta-chlorophenylpiperazine, a metabolite of trazodone, has shown in vitro activeness with a Roche amphetamine urine immunoassay. Testing of half-dozen patients taking trazodone showed that 3 tested falsely positive for amphetamines.¹⁴ Labetalol, promethazine, chlorpromazine, and metformin also take been associated with false positive amphetamine screenings.^15-17 Fenofibrate was identified as the cause of a simulated positive urine amphetamine screening in a patient afterwards 2 dissever immunoassays were positive.¹⁷ In that example, fenofibrate was discontinued, afterward which repeat urine screenings were negative.

Follow-up Drug Testing and Amphetamines

Positive amphetamine immunoassay screening test results tin be confirmed with gas chromatography-mass spectrometry tests (GC-MS). GC-MS separates samples into fragments that are specific to each private compound. Because each fragment blueprint can be linked to a single molecular compound, GC-MS is much more specific than immunoassays and can detect the presence and amount of each drug screened.^eighteen

While urine drug screenings are valuable tools in pain management, they have limitations, including the potential for imitation positives. For amphetamines, most incidents of simulated positives tin can be related to a drug'south construction, merely case reports and retrospective reviews have associated many drugs with false positives. Following a positive drug screening, the possibility of a false positive always should exist considered. A thorough review of the patient's vital signs, relevant history, and recent medications should exist conducted, with additional analysis with more specific tests such as GC-MS, if warranted.

Last updated on: September 7, 2021

Ask The Expert: Fake-Positive Screen for Benzodiazepines

What Medications Could Give a Positive Amphetamine Reading

Source: https://www.practicalpainmanagement.com/resources/diagnostic-tests/ask-expert-false-positive-amphetamine-urine-screens

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