The Vicks VapoInhaler is a small, pocket sized nasal decongestant sold without a prescription. Unlike most over the counter decongestants, its active ingredient is not pseudoephedrine or phenylephrine. It is levmetamfetamine, a compound that is chemically an isomer of methamphetamine. That single fact is why this product shows up so often in questions about workplace and clinical drug testing, and why the answer is more nuanced than a simple yes or no.
The short version: levmetamfetamine can trigger a positive result on an amphetamine or methamphetamine immunoassay screen, and in some cases it can also produce a methamphetamine signal on the GC/MS or LC/MS confirmation step that most laboratories use to verify screening results. That does not mean the donor used illicit methamphetamine. It means the laboratory and the medical review officer (MRO) need to separate the two mirror image forms of the molecule, something a routine confirmation test does not always do by itself.
What levmetamfetamine actually is
Methamphetamine exists as two mirror image molecules, called enantiomers: d-methamphetamine (dextromethamphetamine) and l-methamphetamine (levomethamphetamine, also called levmetamfetamine). They have the same chemical formula and the same mass, which is why many mass spectrometry confirmation methods cannot distinguish them unless a specific chiral, or isomer separating, technique is used.
The two forms behave differently in the body. The d-isomer, found in prescription Desoxyn and in illicit methamphetamine, is the more potent central nervous system stimulant and the form associated with abuse. The l-isomer has much weaker central stimulant effects and is used for its local effect as a nasal decongestant. The current DailyMed label for an over the counter levmetamfetamine nasal inhaler lists levmetamfetamine 50 mg per inhaler as the active ingredient, with a stated purpose of temporary relief of nasal congestion from the common cold, hay fever, or upper respiratory allergies, used by inhaling through the nose as needed, generally not for more than seven days. The DailyMed label for the levmetamfetamine nasal inhaler describes the same active ingredient sold under Vicks VapoInhaler and various store brand names.
Why a screening immunoassay reacts to it
The initial test used in almost every workplace drug testing program, whether a urine cup, a dip card, or an oral fluid device, is an immunoassay. Immunoassays work by using antibodies that bind to a target molecule's general shape. Amphetamine and methamphetamine immunoassays are built to catch the d-isomer family because that is the form associated with misuse, but the antibodies used in many assay chemistries do not fully discriminate between the d and l forms. Because levmetamfetamine shares the same core structure as methamphetamine, a donor who recently used a levmetamfetamine inhaler can produce a nonnegative immunoassay result on an amphetamine or methamphetamine panel. A review of oral fluid drug testing interpretation published in the Annals of the New York Academy of Sciences and available through PubMed Central notes that structurally related compounds, including over the counter sympathomimetics, are a recognized source of nonnegative immunoassay screens that require confirmation before any conclusion is drawn.
Why confirmation testing does not automatically settle it
This is the part that surprises a lot of people. Standard GC/MS or LC/MS confirmation testing identifies the drug by its mass and fragmentation pattern, not by which mirror image form it is. Unless the laboratory runs a dedicated chiral, or stereoisomer specific, method, a confirmed "methamphetamine positive" result can reflect either the d-isomer, the l-isomer, or a mixture of both. A 2026 review of methamphetamine enantiomers in the journal Chirality, indexed on PubMed Central, walks through exactly this problem: routine achiral confirmation cannot tell a d-methamphetamine result from an l-methamphetamine result, and the distinction matters for interpreting a positive test correctly. A separate pharmacology review of R-(-)-methamphetamine, the chemical name for the levo isomer, likewise documents that intranasal l-methamphetamine use produces detectable methamphetamine and amphetamine in urine, oral fluid, and plasma, which is why isomer specific testing exists as a follow up step rather than a routine default. Both of these sources are reviewed on PubMed Central and summarized in a 2023 pharmacology review, and both describe the chiral separation methods laboratories can apply.
The federal rule that governs this exact situation
For safety sensitive transportation employees tested under US Department of Transportation rules, this scenario is specifically anticipated. Under 49 CFR Part 40, the regulation that governs DOT drug testing programs, the medical review officer has the authority to request that an HHS certified laboratory test a confirmed positive specimen for the D and L stereoisomers of amphetamine and methamphetamine when the MRO determines that step is necessary to make a correct verification decision. This isomer testing option exists precisely because of products like levmetamfetamine inhalers and prescription or over the counter compounds that share a core amphetamine structure. The current text of this provision is available in 49 CFR 40.141, which describes how the MRO obtains information for the verification decision, including stereoisomer testing. Non DOT federal workplace testing programs follow a parallel structure under the HHS Mandatory Guidelines, and employers should always check which rule set applies to a given testing program rather than assume one set of procedures covers every case.
What a donor should tell the MRO
A donor who has recently used a nasal decongestant inhaler and later tests nonnegative on an amphetamine or methamphetamine panel should tell the medical review officer, truthfully and specifically, what product was used, when, and how often. The MRO conducts a confidential interview as part of the verification process and can order additional testing, including isomer separation, before verifying a result as positive. The donor does not need to guess at the chemistry. The donor's job is to disclose the product name and timing accurately; the laboratory and the MRO handle the scientific determination. Keeping the original package or a receipt can help establish the timeline, though it is not required for the MRO process to work.
Nobody should attempt to explain away a result with a product they did not actually use, and nobody should be advised to use an over the counter product specifically to try to influence a test outcome. The purpose of disclosure is accuracy, not evasion, and the MRO process exists to tell the difference between the two.
What this means for employers and program administrators
Employers running a drug free workplace program generally do not need to change panel design because of this issue. The screening and confirmation process, paired with MRO review, is built to catch and resolve exactly this kind of interference. What employers should do is make sure their MRO contract or third party administrator actually has access to isomer separation testing when a case calls for it, since not every laboratory runs that method as a routine option and it sometimes has to be specifically requested. Employers should also avoid drawing conclusions from a screening result alone. A nonnegative immunoassay is a trigger for confirmation and MRO review, not a verified positive, and policies and training materials should say so plainly.
| Over the counter product | Active ingredient | Panel it can affect | What usually resolves it |
|---|---|---|---|
| Vicks VapoInhaler and similar levmetamfetamine inhalers | Levmetamfetamine (l-methamphetamine) | Amphetamine or methamphetamine immunoassay, sometimes methamphetamine confirmation | MRO interview plus stereoisomer (D,L) confirmation testing when needed |
| Sudafed and other pseudoephedrine decongestants | Pseudoephedrine | Amphetamine or methamphetamine immunoassay | Structural comparison on confirmation; distinct retention time and mass pattern from methamphetamine |
| Phenylephrine based decongestants | Phenylephrine | Limited evidence of cross reactivity on most current immunoassay chemistries | MRO review of product disclosure; confirmation testing clarifies the specific analyte |
| Dextromethorphan cough suppressants | Dextromethorphan | PCP immunoassay in some assay chemistries at high doses | Confirmation testing distinguishes dextromethorphan from phencyclidine |
The amphetamine and methamphetamine immunoassay panel used in most drug test cups, dip cards, and oral fluid devices is not identical across every manufacturer, and cutoff concentrations and antibody specificity vary by assay chemistry. Anyone building or running a testing program should ask the laboratory or test manufacturer directly which analytes and cross reactants a given panel is validated against, rather than assume every amphetamine class test behaves the same way. For background on how the amphetamine and methamphetamine panels are structured and how they differ, see this related explanation of amphetamine versus methamphetamine drug test panels, and for a full walkthrough of what happens after a nonnegative screen, see this overview of the medical review officer process.
Evidence level, stated plainly
The cross reactivity described here is not theoretical or anecdotal. It follows directly from the shared chemical structure of d- and l-methamphetamine, it is documented in the pharmacology and chirality literature cited above, and it is explicitly addressed in federal transportation drug testing regulation through the stereoisomer testing option available to MROs. This is a different situation from many other over the counter medications, where cross reactivity evidence is limited or absent. With levmetamfetamine inhalers, the evidence for immunoassay cross reactivity, and in some instances confirmation level interference, is well established, which is exactly why the regulation builds in a specific resolution pathway rather than leaving it to guesswork.
Laboratories and testing program administrators who need drug test cups, dip cards, or oral fluid collection devices for an amphetamine or methamphetamine panel can find current options in the drug test cup collection at American Screening Corporation.
Frequently asked questions
Can Vicks VapoInhaler make a drug test come back positive for methamphetamine?
It can trigger a nonnegative immunoassay screen for amphetamines or methamphetamine, and in some cases it can show up on a confirmation test as methamphetamine because routine confirmation does not separate the d and l isomers. A nonnegative screen is not the same as a verified positive result.
Is levmetamfetamine the same as illegal methamphetamine?
No. Levmetamfetamine is the l-isomer, a mirror image form of the methamphetamine molecule with much weaker stimulant effects, used in over the counter nasal inhalers. Illicit methamphetamine is predominantly the d-isomer, which has stronger central nervous system effects. They share a chemical backbone but are not the same substance in effect or in legal status.
How does a laboratory tell the difference between the two forms?
Standard GC/MS or LC/MS confirmation identifies the molecule's mass and fragmentation pattern, which is the same for both isomers. A separate chiral, or stereoisomer specific, testing method is required to distinguish d-methamphetamine from l-methamphetamine, and this method is typically ordered by the medical review officer only when needed.
What should someone do if they used a decongestant inhaler before a drug test?
Tell the medical review officer which product was used and when, during the verification interview. The MRO can request isomer separation testing or further laboratory review before making a final determination. This disclosure should always be truthful and should never be used to explain a result that did not actually come from the disclosed product.
Does federal law address this specific interference?
Yes, for transportation workers covered by US Department of Transportation testing rules. The regulation at 49 CFR Part 40 gives the medical review officer the authority to request D and L stereoisomer testing on confirmed positive specimens before verifying a result. Non DOT programs generally follow a parallel process under HHS Mandatory Guidelines, and employers should confirm which framework governs their specific program.
Should employers change their testing panel because of this issue?
Generally no. The combination of immunoassay screening, laboratory confirmation, and MRO review is designed to catch and resolve this kind of interference. Employers should confirm their MRO or laboratory has access to isomer testing when a case requires it and should train staff not to treat a screening result alone as a confirmed positive.
This article is general information about drug testing science and procedure, not medical or legal advice. Employers and donors should consult their medical review officer, laboratory, or legal counsel for guidance specific to an individual case.
