Selegiline is a prescription medication used to manage Parkinson disease symptoms and, in a transdermal patch form, major depressive disorder. It is not a controlled substance. Yet selegiline is one of the few prescription drugs that can turn an amphetamine drug screen positive for a reason that is different from almost every other medication on this topic. Most "does this medication cause a false positive" questions involve a drug whose chemical structure merely resembles amphetamine closely enough to trigger an antibody in a screening immunoassay, a true cross reactivity problem that a confirmation test clears up. Selegiline is not like that. Its own metabolism manufactures real amphetamine and real methamphetamine molecules inside the body, and those molecules show up in urine because they are genuinely there. This is the single most important point in this article, and it is worth saying plainly: a selegiline related positive is not a laboratory error. It is a true positive for the amphetamine drug class. What separates a legitimate selegiline user from someone who used illicit methamphetamine is a detail that standard testing does not automatically check, the isomer, or mirror image form, of the molecule.
What Selegiline Is and How the Body Breaks It Down
Selegiline is marketed as an oral capsule or tablet (generic selegiline hydrochloride, also sold historically under names like Eldepryl and Zelapar) for Parkinson disease, and as a transdermal patch (Emsam) for depression. The drug label for selegiline hydrochloride states that the major plasma metabolites are N-desmethylselegiline, L-amphetamine, and L-methamphetamine, and that peak levels of these metabolites after a single dose can run several times higher than the parent drug itself, meaning the body is producing a meaningful amount of amphetamine class compound with every dose. The FDA label for selegiline hydrochloride capsules describes this metabolic pathway in detail.
The transdermal version of selegiline carries an even more specific statement. Its label explains that selegiline is metabolized through N-dealkylation or N-depropargylation into R(-)-methamphetamine and, further, into R(-)-amphetamine, and that these metabolites are excreted largely unchanged in urine. The transdermal selegiline label states this metabolism directly. In plain terms, whether a person takes the capsule, the tablet, or wears the patch, the liver converts part of the dose into molecules that are chemically identical to the amphetamine and methamphetamine that a workplace or clinical drug panel is built to detect.
Why This Is Not Ordinary Cross Reactivity
Most posts in this series describe a medication whose structure is close enough to a target drug that a screening antibody binds to it by mistake, producing a positive reading that a more specific confirmation test later clears. Selegiline does not need to fool anything. The amphetamine class immunoassay used in cups, dip cards, and oral fluid devices is designed to flag amphetamine and methamphetamine in urine above a set cutoff, and selegiline's own metabolites are amphetamine and methamphetamine. A confirmation test run the standard way, meaning the instrumented method that identifies and quantifies the specific drug or metabolite present, will also correctly identify methamphetamine and amphetamine in the specimen, because they are actually there. Federal cutoff rules set the amphetamine and methamphetamine immunoassay threshold at 500 nanograms per milliliter and the confirmatory threshold at 250 nanograms per milliliter, and selegiline metabolite levels can clear both thresholds. So neither the screening step nor a routine confirmation step will, by itself, show that the source was a prescription rather than illicit drug use. That distinction depends on the isomer.
The Isomer Question: Why Mirror Image Molecules Matter
Amphetamine and methamphetamine each exist in two mirror image forms, called enantiomers or isomers, usually labeled d- (dextro) and l- (levo). The two forms share the same chemical formula and the same basic structure, but they are arranged as mirror images of each other, similar to a left hand and a right hand. Illicit methamphetamine sold on the street is overwhelmingly the d- isomer, which has stronger central nervous system stimulant effects. Selegiline's metabolites are different. The transdermal selegiline label states explicitly that its methamphetamine and amphetamine metabolites "are all levorotatory (l-) enantiomers and no racemic biotransformation to the dextrorotatory form... occurs." This statement appears directly in the metabolism section of the label. In other words, selegiline produces only the l- form, never the d- form associated with illicit use.
A standard immunoassay screen cannot tell the two isomers apart, and a routine GC/MS or LC-MS/MS confirmation, run the way most laboratories run it by default, identifies the drug class and quantity but does not automatically separate d- from l- methamphetamine or d- from l- amphetamine. Separating the isomers requires an additional, specialized chiral (enantiomer specific) analysis, which a certified laboratory can perform, but typically only when it is specifically requested, usually because a medical review officer has learned that the donor reports a prescription that could explain an l- isomer result, such as selegiline. Without that extra step, a confirmed positive for amphetamine and methamphetamine looks identical on paper whether the source was a prescription or illicit use.
| Testing stage | What it measures | What it shows with selegiline use |
|---|---|---|
| Initial immunoassay screen (cup, dip card, oral fluid device) | Amphetamine class molecules above the cutoff | Positive, because L-amphetamine and L-methamphetamine are genuinely present |
| Standard instrumented confirmation | Identifies and quantifies the specific drug or metabolite present | Confirms amphetamine and methamphetamine are present, but does not separate isomer by default |
| Chiral, isomer specific confirmation (requested separately) | Separates the d- and l- mirror image forms | Shows the l- isomer only, consistent with selegiline, not the d- isomer typical of illicit methamphetamine |
| Medical review officer verification interview | Prescription history, medical records, and all lab data together | Donor discloses the selegiline prescription so the MRO can evaluate a legitimate medical explanation |
How the Medical Review Officer Review Works
A confirmed positive amphetamine result does not become a final, reportable outcome on its own. Federal drug testing rules require a medical review officer, a licensed physician trained in this role, to review every laboratory confirmed non-negative result before it is reported to an employer. For results involving amphetamines, the rule is specific about how that review works: the MRO must verify the test as positive unless the employee presents a legitimate medical explanation for the drug or metabolite found in the specimen, and the employee carries the burden of presenting that explanation, generally at the time of the verification interview. The federal rule governing MRO verification of amphetamine results lays out this standard. A valid prescription, consistent with applicable law, generally counts as that explanation, and the MRO is not permitted to second guess whether the prescribing clinician should have written it.
In a selegiline case, this means the donor should be prepared to tell the MRO about the prescription and, if asked, provide supporting documentation, such as a pharmacy record or a statement from the prescribing clinician. Depending on the circumstances and the laboratory's capabilities, the MRO may also request that the original or split specimen undergo the additional isomer specific analysis described above, since a result showing only the l- isomer is consistent with selegiline and not with illicit methamphetamine. The MRO weighs all of this information together. Non-DOT federal and many private sector workplace drug testing programs follow a similar legitimate medical explanation framework, and employers and MROs working outside the DOT system can find general program information through the Substance Abuse and Mental Health Services Administration. SAMHSA publishes drug free workplace and drug testing program resources for employers and medical review officers.
What Employers and Donors Should Know
Employers should never ask a donor to withhold medication information before a test, and a donor who is prescribed selegiline should disclose it as part of the normal verification process rather than waiting to be asked. The documentation that matters most is proof of a valid, current prescription. Employers should not take adverse action based on a laboratory confirmed positive alone. The verification step with a medical review officer exists specifically to sort out cases like this one, where the chemistry of a legitimate medication overlaps with a drug class on the panel. Collection sites and laboratories that run amphetamine and methamphetamine panels as part of a standard drug test cup or dip card program should be prepared to route any confirmed positive to an MRO rather than reporting it directly to a decision maker, and employers who build or manage drug free workplace programs can review panel configurations and collection devices designed for this kind of screening through a supplier's standard catalog, such as a drug test cup collection. Standard multi-panel drug test cups typically include the amphetamine and methamphetamine panel referenced in this article.
Understanding the difference between the initial amphetamine panel and the methamphetamine specific panel also helps explain why a selegiline case can look confusing on a lab report. A closer look at how these two related panels are built and reported is covered in a related discussion of amphetamine and methamphetamine testing. This companion article walks through how AMP and mAMP panels are structured. The verification process itself, including what a donor can expect during an interview and what documentation helps, is covered in more general terms in a dedicated explanation of the medical review officer process. That article explains the MRO process for employers in more detail.
Frequently asked questions
Does selegiline show up on a standard amphetamine drug test panel?
Yes. Selegiline is metabolized into L-amphetamine and L-methamphetamine, which are excreted in urine and can be detected by a standard amphetamine class immunoassay screen and by routine instrumented confirmation testing.
Is a selegiline related positive really a false positive?
Not in the usual sense. The screening and standard confirmation results are chemically accurate. What needs clarification is the source of the result, a prescription metabolite rather than illicit drug use, which is sorted out through isomer specific testing and medical review officer review rather than through a simple retest.
Can a routine lab confirmation alone clear a selegiline related positive?
Not by itself. A routine confirmation identifies the drug class and amount present but does not automatically separate the d- and l- isomers. A separate, chiral confirmation test is generally needed to show that only the l- isomer associated with selegiline is present.
What should someone taking selegiline do before a drug test?
Disclose the prescription to the collector or the medical review officer and be ready to provide documentation, such as a pharmacy record, if asked during the verification interview. This is general information, not medical advice, and anyone with questions about their prescription should speak with their prescribing clinician.
How does a medical review officer handle a selegiline case?
The MRO reviews the confirmed laboratory result, interviews the donor, and considers whether a legitimate medical explanation, such as a valid selegiline prescription, accounts for the result. The MRO may request additional isomer specific testing before making a final verification decision.
Does selegiline affect other drug test panels, such as THC or opiates?
There is no published cross reactivity evidence tying selegiline to the THC, opiate, cocaine, or PCP panels. The documented interaction is limited to the amphetamine and methamphetamine class, through selegiline's own metabolism.
This article is general educational information about drug testing science and process. It is not legal or medical advice. Employers should consult qualified counsel for compliance questions, and individuals should consult their prescribing clinician or a medical review officer about their own results.
