Medicines as a Cause of Unusual Hair-Test Results

A positive result in a hair analysis is a shock for many of those affected: you feel confident that you have not consumed any illegal drugs, and suddenly there is an abnormal result in the laboratory report. This is particularly stressful when it comes to the MPU, the workplace, a court case or a custody dispute.

In fact, medications can affect drug tests. Cross-reactions are possible, especially with simple preliminary tests, so-called immunoassays. The test not only reacts to the drug being sought, but also to chemically similar active ingredients or degradation products. With a professional hair analysis, the risk of false-positive results is lower than with rapid urine tests. However, it is not infallible either, especially if findings are misinterpreted or medications taken are not documented.

It is therefore important to note that an abnormal finding does not automatically mean illegal drug use. It must be classified technically and, if necessary, checked by specific confirmation analysis.

How does a hair analysis for drugs actually work?

A hair analysis examines whether drugs, medications or their breakdown products can be detected in the hair. As a hair grows, substances from the blood can be stored in the hair matrix. External influences, such as smoke, dust or contaminated surfaces, can also play a role. Reputable laboratories therefore take not only the pure detection of a substance into account, but also concentrations, metabolites and plausibility.

Head hair is usually examined to prove abstinence. As a rough rule of thumb: one centimeter of head hair corresponds to approximately one month of detection period. Depending on the question, several months can be viewed retroactively.

There are two important stages in laboratory analysis:

1. Screening or search test: This roughly checks whether a substance class is suspicious. Immunological preliminary tests are quick, but more prone to cross-reactions.
2. Confirmatory analysis: Procedures such as GC-MS or LC-MS/MS identify substances much more precisely. You can often distinguish between illegal drugs, legally prescribed medications and certain breakdown products.

The Society for Toxicological and Forensic Chemistry points out in its guidelines and statements that forensic toxicological hair analyzes place high demands on quality assurance, methods and interpretation. Positive hair findings must be assessed by an expert, especially if they have legal or expert consequences. Sources: GTFCh guidelines, GTFCh/DGVM statement on hair analysis

Which medications make the hair analysis positive for drugs?

The most important distinction is: Some medications cause a true positive result because they themselves belong to the substance group being sought. Others can trigger a false-positive reaction in non-specific preliminary tests, even though there is no illegal consumption.

Over-the-counter medications: cold medicines, painkillers and cough syrups

When many people think of drug tests, the first thing that comes to mind is illegal substances. However, over-the-counter or previously over-the-counter preparations can also be problematic.

Cough syrups containing codeine are a classic example. Codeine is partially metabolized in the body to morphine. If a test for opiates is positive, this could be explained by codeine. This is not necessarily a “false positive”, but rather a medically explainable positive finding.

Pseudoephedrine or ephedrine from cold and cold medicines can also be problematic in simple immunoassays because they are chemically related to amphetamines. However, a precise LC-MS/MS analysis should clarify whether amphetamine, methamphetamine or just a legal cold drug is actually present.

When using Ibuprofen or Naproxen , special care is important in the formulation: In modern hair analyzes with confirmatory analysis, these painkillers usually do not lead to a positive drug detection. Individual reports of cross-reactions tend to concern older or simple rapid urine and saliva tests.

Prescription medications and psychotropic drugs

When it comes to prescription medications, the situation is more complex. Some active ingredients are themselves psychoactive or belong to substance groups that are also examined in drug tests.

ADHD medications are particularly relevant. Lisdexamfetamine, known from Elvanse, is converted into dexamfetamine in the body. A positive amphetamine result can therefore be medically explained if taken correctly. Methylphenidate, known from Ritalin or Concerta, is not an amphetamine. It can be detected separately in specialized analyzes but should not automatically be assessed as illegal amphetamine use.

Antidepressants can also show up in preliminary immunological tests. In the specialist literature, bupropion, sertraline and venlafaxine, among others, are associated with false-positive screening results. Such findings particularly concern urine immunoassays. With a high-quality hair analysis, a confirmatory analysis should usually be able to clarify the difference.

With opioids such as tramadol, tilidine, fentanyl or oxycodone, a lot depends on the test panel. Some laboratories only test classic opiates such as morphine and codeine, others record a broader spectrum of opioids. Anyone who is prescribed such medication by a doctor should definitely mention it before the hair removal.

Benzodiazepines and sleeping pills such as diazepam, lorazepam, oxazepam or zolpidem may also be relevant. The same applies here: Evidence can be medically explained if the prescription, dosage and period of intake are clearly documented.

MPU hair analysis Medication: What to do if you are prescribed medication?

When it comes to the MPU or proof of abstinence, it’s not just what is medically plausible that counts. It is also crucial whether the intake was documented transparently beforehand.

Anyone who takes medication regularly or for a short period of time should collect the following documents before the hair analysis:

1. Current medication plan
2. Recipe copies
3. Medical certificate with diagnosis, active ingredient, dosage and period of intake
4. Information leaflet or proof of medication for over-the-counter preparations
5. Written information about all preparations on the laboratory or institute questionnaire

Particularly important: Do not only give strong medications. Over-the-counter painkillers, cold medicines, sleeping pills, CBD products, dietary supplements and herbal preparations may also be relevant for the assessment.

Important note for the MPU:
Disclose any medication taken in writing before hair collection. Although subsequent explanations are possible, they are often viewed more critically by experts than complete documentation from the start.

Medical cannabis and hair analysis

Medical cannabis is a special case. Anyone who is prescribed cannabis by a doctor is not consuming it illegally, but may still have THC or THC metabolites in their hair. This can still be relevant for fitness to drive because experts not only consider the legality of the intake, but also performance, risk of misuse, dosage, indication and medical supervision.

Therefore, medical cannabis should never be mentioned “just in passing”. Medical documents, proof of dosage and professional advice are particularly important here.

Rescue from false findings: Confirmatory analysis

When a drug test is positive, the most important question is: is it a mere screening finding or a confirmed analysis?

A screening test can provide clues but is not definitive. Immunoassays work with antibody reactions. These tests are sensitive but not always highly specific. Therefore, chemically similar substances can trigger a cross-reaction.

A confirmatory analysis using GC-MS or LC-MS/MS is significantly more precise. These processes separate and identify substances based on their chemical properties. In many cases, this allows the laboratory to distinguish whether a finding was caused by a medication, a legal breakdown product or an illegal drug.

The US literature and government information on drug testing also emphasizes that positive screening results should be confirmed when making significant decisions. SAMHSA describes, for example, that confirmatory tests using GC/MS or LC/MS/MS are used to confirm positive screening results. Source: SAMHSA Drug Testing Resources, NCBI Confirmatory Testing Bookshelf

If the laboratory still reports a positive result, the following steps can be considered:

1. Request complete laboratory report
2. Check whether screening or confirmatory analysis was carried out
3. Submit medication list, prescriptions and certificates
4. Request B sample analysis or second assessment
5. Involve an independent toxicologist or specialist lawyer if there is a risk of legal consequences

Important: Do not hastily argue that the test is “wrong”. A factual formulation is better: The finding requires explanation because there is documented medication intake or a possible cross-reaction.

What can distort a hair analysis?

In addition to medications, other factors can complicate the interpretation of a hair analysis:

• cosmetic treatments such as bleaching, coloring or perms
• very short or severely damaged hair
• external contamination from smoke, powder or close contact with substances
• incorrect sample storage or mix-ups, rare but possible
• missing information on medications and dietary supplements
• unclear cut-off values or unsuitable examination method

A cut-off value is the limit above which a laboratory considers a result to be positive. If a substance is below this value, it may be present analytically, but depending on the regulations it is not assessed as a positive violation of abstinence.

Checklist for patients before hair analysis

Before a hair analysis, you should proceed as structured as possible:

1. Write down all medications from the last few months
2. Also list over-the-counter remedies, cough syrups, painkillers and sleeping pills
3. Collect prescriptions and pharmacy receipts
4. Obtain a medical certificate with the active ingredient, dosage and period
5. Inform the laboratory or collection point in advance
6. Fill out the questionnaire completely and truthfully
7. Do not take any new preparations without consulting a doctor
8. If the result is positive, request the complete laboratory report immediately

FAQ: Frequently asked questions about medications and hair analysis

Can medications have a positive effect on a hair analysis for drugs?

Yes. Certain medications can affect drug tests. In particular, cold medicines containing ephedrine or pseudoephedrine, ADHD preparations, cough syrups containing codeine, opioids or psychotropic drugs can cause abnormal findings or trigger cross-reactions in simple preliminary tests. With modern confirmation analysis, the cause can often be clarified more precisely.

Which antidepressants work on a drug test?

Bupropion, sertraline and venlafaxine in particular are mentioned in connection with false-positive immunoassay results, for example for amphetamines or other substance classes. This particularly applies to urine or rapid tests. A precise confirmatory analysis using GC-MS or LC-MS/MS can usually clear up the error.

How can you prove that a drug test was positive due to medication?

The most important thing is a complete medication plan, copies of prescriptions, medical certificates and a complete laboratory report. In addition, it should be checked whether a specific confirmatory analysis was carried out. This can often distinguish the chemical fingerprint of a medication from an illegal drug.

Does ibuprofen work on hair analysis?

In high-quality hair analyzes with confirmatory analysis, ibuprofen usually does not have a positive effect on illegal drugs. Rare reports of cross-reactions tend to involve inaccurate urine, saliva or rapid tests. Anyone who has taken ibuprofen regularly or in high doses should still declare it.

Conclusion: Preparation protects against the positive shock

Medications can have a positive effect on a hair analysis for drugs, but not every abnormal finding means illegal consumption. What matters is whether it is a non-specific screening test or a precise confirmatory analysis.

Anyone who is faced with an MPU, proof of abstinence or legal proceedings should never conceal medication. Prescriptions, certificates and a complete medication plan are the best protection against misunderstandings. Modern laboratory methods such as GC-MS and LC-MS/MS can clarify many cross-reactions, but only if the relevant information is available in a timely manner.

This article is for general information purposes and does not replace medical, toxicological or legal advice. In the event of a positive result with possible consequences, professional advice should always be sought.

Sources and further information

SAMHSA