The Scientific Advances in Psychoactives Versus Artifacts in Amphetamine Analysis

Abstract

Psychoactive substances, including illicit drugs, prescription medications, and novel psychoactive compounds, are frequently analyzed in biological and in non-biological samples. Interpreting results is paramount for ensuring proper medical treatments and judicial decisions. However, false-positive results—where a sample is incorrectly identified as containing a psychoactive substance—remain a persistent issue. In other words, it is important to invest in understanding the meaning of toxicological results. Cross-reactivity in immunoassays, sample contamination, analytical interference with certain endogenous and exogenous substances, inadvertent and accidental exposure due to environmental contamination, second-hand smoke inhalation, or unintentional dermal or mucosal contact with drug residues are some of the major issues to consider. This perspective highlights major sources of artifacts in interpreting amphetamine analytical results in order to provide proper toxicological interpretations.

1. Perspective

Methamphetamine is a member of the amphetamine-type stimulants class that acts on the central nervous system to release monoamines such as dopamine, norepinephrine, and serotonin [1]. Methamphetamine can cause abuse, addiction, euphoric effects, and toxicity, with adverse consequences including cardiovascular problems, paranoia, psychosis, and even mortality. In the context of doping, methamphetamine is classified as a stimulant, and its use in sports is primarily for its performance-enhancing effects, namely increased alertness and reaction time, and enhanced focus, concentration, and decision-making, which can be beneficial in sports requiring quick reflexes. Indeed, by stimulating the central nervous system, methamphetamine delays fatigue and allows athletes to train or compete at a high intensity for more extended periods. Moreover, the euphoric effects of methamphetamine can boost an athlete’s confidence and risk-taking behavior, potentially enhancing performance in high-stakes situations [2]. Taken together, it may offer doped athletes an unfair advantage over clean competitors [3].

Methamphetamine has a chiral center; as such, it can produce a pure (D or S(+)) isomer, pure (L or R(-)), an exact 50/50 racemic mixture, or other proportions in between. (L) methamphetamine is a good decongestant, but it is otherwise unenjoyable and has no market as a drug of abuse [4,5]. The (D) isomer is a psychoactive central nervous system stimulant and is produced by some very large-scale drug cartels. The (D) isomer (i.e., the d-methamphetamine) is controlled by anti-doping agencies and may cause an Adverse Analytical Finding (AAF—a positive test result for a prohibited substance or its metabolites in an athlete’s sample). The Minimum Reporting Level (MRL) refers to the specific concentration threshold established for certain non-threshold substances, above which a laboratory must report the finding as an AAF. Regarding the d-methamphetamine, the MRL has been set to 50 ng/mL. The drug can be consumed in several ways, each affecting its effects’ onset, intensity, and duration. Primary routes include ingestion of pills, capsules, or dissolved in liquids; smoking (inhalation)—“Crystal Meth”; intravenous injection—“Slamming”; and snorting (insufflation)—“Bumping” or “Blowing”. Methamphetamine undergoes hepatic metabolism, primarily in the liver, through several pathways. Namely, N-demethylation converts methamphetamine into amphetamine (active metabolite). Elimination occurs mainly through urine [1].

In the diagnosis of voluntary methamphetamine exposure, it is highly important to pay attention to several confounding artifacts that may lead to false-positive results and, therefore, erroneous clinical and forensic conclusions. This editorial highlights precisely this problem in different scenarios.

Illegally manufacturing (referred to as “cooking”) methamphetamine in clandestine laboratories is easy, and has been practiced for more than 50 years. Due to the intensity of the odor they give off, methamphetamine production facilities are typically located in rural areas and away from large towns. Typically, ephedrine and pseudoephedrine are used as precursors, since these are structurally similar compounds that share a core phenethylamine skeleton. Specifically, methamphetamine contains a methyl group attached to the amine group, increasing its lipophilicity and central nervous system activity. On the other hand, pseudoephedrine, a diastereomer of ephedrine, possesses a hydroxyl group on the beta-carbon, which limits its ability to cross the blood–brain barrier compared to methamphetamine. These small structural differences significantly impact pharmacodynamics, with methamphetamine acting as a potent CNS stimulant and pseudoephedrine primarily functioning as a nasal decongestant with limited psychoactive effects. Due to their structural similarity, pseudoephedrine can cause false-positive results in certain drug tests (e.g., immunoassays) designed to detect methamphetamine [6]. For instance, a false-positive rate of 75% was reported with the Microgenics DRI amphetamine–methamphetamine immunoassay due to the presence of pseudoephedrine in 1104 urine samples [7,8,9]. Another drug that has been associated with false positive results for amphetamine is 1,3-dimethylamylamine (DMAA). DMAA has sympathomimetic activity and is an ingredient in some dietary and weight-loss supplements [10,11]. Bupropion, which is used as an antidepressant and smoking cessation aid, is also structurally similar to amphetamine, and has been associated with false-positive screenings, with the threohydrobupropion metabolite being reported to be the main substance responsible for the false-positive results in the amphetamine immunoassays [12,13,14,15,16]. Also, patients taking trazodone, nefazodone, and etoperidone can produce urine with sufficient meta-chlorophenylpiperazine (m-CPP) metabolite to result in a false-positive [17,18]. Additionally, the phenylpropanolamine and the phenylephrine, α1-adrenergic agonists used as decongestants, can cause false-positive results for amphetamines in immunoassay tests [8,19]. Selegiline, a selective, irreversible monoamine oxidase-B inhibitor used for reducing symptoms in early-stage Parkinson’s disease, is also metabolized to l-methamphetamine and l-amphetamine, and may lead to false-positive immunoassays for amphetamines [20,21]. Figure 1 presents structural similarities of compounds that can lead to false-positive results in amphetamine analysis.

Therefore, positive immunoassay results that may change the management of a patient’s condition should be quickly verified with confirmatory testing to minimize unfavorable consequences. Finally, it is relevant to highlight that different biological samples (e.g., urine, plasma, hair, or oral fluid) and detection methods have different sensitivities and specificities, which may significantly affect the results. Liquid Chromatography–high resolution/high accuracy mass spectrometry (LC-HRMS) proved to be highly sensitive and specific, particularly for distinguishing methamphetamine enantiomers [22,23,24].

Besides chemical cross-reactivity in analytical diagnosis, during the manufacturing process and after smoking the drug, methamphetamine residues, airborne particles, gases, and volatile organic compounds (VOCs) are released into the surrounding environment [25]. These residues can settle onto surfaces, and are further spread by dermal, oral, or air transfer [26,27]. Therefore, exposure to methamphetamine in those who do not take methamphetamine themselves may occur due to contact with the drug from a first-hand user, or when someone frequents a place that has been contaminated either by drug use or with a material that is contaminated [28]. Toxic residues can spread throughout the area, persist for years, and harm future occupants. Moreover, when methamphetamine is produced or used in a dwelling, interior surfaces become contaminated with residues and pose serious health risks to anyone in the dwelling [29]. Already in 2025, it was demonstrated that smoking methamphetamine can subsequently contaminate air and surfaces with drug residue in public spaces such as public transit, leading to potential second-hand exposures among transit operators, as occurs with hotel guests, and leading to a positive result following a drug test [30]. The authors also concluded that protection and proper cleaning should be ensured for visitors to avoid the stress of witnessing and responding to drug abuse. Indeed, recreational methamphetamine production, and heavy use can result in dwelling contamination that is difficult to detect. Therefore, several chemical and analytical options for eliminating trace methamphetamine contamination have been developed to avoid the risk of contamination [31]. This contamination is so obvious that secondary exposure to methamphetamine residue can still cause a range of health problems, including respiratory distress, headaches, nausea, dizziness, and eye and skin irritation, meaning that systemic effects are occurring [32]. Professional cleanup is needed for removing contaminated materials, deep-cleaning surfaces, and sometimes replacing drywall or flooring. In other words, the manufacture and recreational use of methamphetamine can result in widespread chemical contamination throughout a property, and is a concern for homeowners or residents in countries around the world [33]. Chemical decontamination typically employs chemicals with strong oxidant properties, such as hydrogen peroxide (H₂O₂), capable of neutralizing or decomposing environmental contaminants. These may be used as washing solutions or applied to surfaces such as fog or foam [34]. Regarding smoking, a study aiming to assess the amount of methamphetamine contamination produced on different surfaces after smoking evidenced a methamphetamine order retention for acrylic >  plasterboard >  metal >  painted wood >  tile [35]. An accumulation rate was also established individually for each surface, proving that acrylic accumulates the greatest amounts of methamphetamine across all surfaces in this research [35]. In any bar, as in other public places, where methamphetamine is regularly consumed, residues accumulate over weeks, and can persist for even 4 weeks after cessation of consumption [35].

From 2010 to June 2022, Mexican authorities secured nearly 700 clandestine laboratories of methamphetamine, representing only 46% of all clandestine laboratories that have been seized in the country (https://insightcrime.org/news/methamphetamine-production-mexico-toxic-environment/, accessed on 19 April 2025). This reality contaminates the environment, and the classical Water and Sewage Treatment Plants do not efficiently remove methamphetamine residues [36,37]. Indeed, massive production, consumption, and inefficient disposal in water treatment plants of drugs of abuse have led to their pseudo-persistent presence as environmental contaminants [38]. Typically, illicit drugs can reach the water cycle through accidental or deliberate disposal of drugs by clandestine laboratories and trafficking networks [39]. Moreover, if numerous people in a specific region are consuming methamphetamine, the drug enters the wastewater through the feces and urine of users. Accordingly, recently methamphetamine has been recognized as an emerging organic contaminant, as it was widely detected in the aquatic environment via wastewater effluent discharge [40]. This reality represents an additional source of contamination, especially in major methamphetamine countries producers. Even simple gestures such as drinking water not from closed bottles and washing hands and teeth with a tap are potential sources of contamination.

An additional source of accidental exposure may come from oral fluid due to swallowing residues from contaminated lips, oral fluid, hands, food, or drinks. Specifically, oral fluid is an alternative biological matrix to urine and plasma for drug-of-abuse testing [41]. Indeed, in a study that analyzed fifty real oral fluid samples by a validated method, methamphetamine was detected in all authentic samples in concentration ranges of 20.412–441.370 ng/mL [42]. Another study was designed to describe the pharmacokinetics of methamphetamine and amphetamine in human oral fluid and plasma after controlled oral methamphetamine administration to determine whether oral fluid concentrations can be used to predict plasma concentrations. In oral fluid, methamphetamine was detected as early as 0.08–2 h, with a maximum concentration of 24.7–312.2 g/L (10 mg) and 75.3–321.7 g/L (20 mg), and occurred at 2–12 h after administration [43]. Studies report that both oral and smoking administration of methamphetamine can represent a substantial buccal contamination of oral fluid, a fact that has been documented for many years [44].

Another artifact may come from old formulations of VapoRub inhaler^®. The original version (Procter & Gamble’s) contained over 100 mg of levmetamfetamine (L), which was reduced to 50 mg in 2009. At the beginning of 2014, the formulations switched to a homeopathic formulation, removing the levmetamfetamine and leaving camphor, menthol, methyl salicylate (wintergreen scent), and Siberian Fir oil. Therefore, cross-contamination by Vicks VapoRub^® is not the case, except if old formulations (fabricated data before 2014) are used. However, several generic versions of levmetamfetamine-containing nasal spray decongestants became commercially available from both brick-and-mortar and online retailers [4]. All available generic versions typically contain 50 mg levmetamfetamine per inhaler, and include the same recommended administration instructions as described above for Vicks VapoRub^®.

2. Concluding Remarks

Accidental transfer and inadvertent exposure are a reality, especially when using highly sensitive methods, such as those followed in anti-doping laboratories [45]. Understanding the problem from various perspectives, including the potential sources, current case studies and research, and the available laboratory detection techniques, is essential to reduce the risk of unintentional exposure and better elucidate deliberate administration cases. In other words, passive methamphetamine exposure is a serious, but often overlooked, risk, especially after: (i) exchanging oral fluids (e.g., kissing) with someone who previously consumed methamphetamine; (ii) contact with places where methamphetamine is a probable contaminant, such as former methamphetamine laboratories, homes, hotels, gym equipment, furniture, bars, clubs, public areas, and enclosed or poorly ventilated spaces; (iii) shaking hands, hugging, or sharing personal items (e.g., towels, water bottles) with a person who has methamphetamine on the skin and lips; (iv) handling money, bags, or paraphernalia contaminated with methamphetamine; and (v) eating food prepared by someone with methamphetamine residue on their hands, drinking from a contaminated water bottle or glass, consuming spiked drinks, or tampered food in social situations.

Nowadays, athletes face increasing risks of testing positive for banned substances due to unintentional exposure to various sources of contamination. Such exposures can result in an AAF-a positive doping test, which may lead to sanctions when the athlete is unaware of exposure to a prohibited substance [46]. Therefore, accurately detecting an AAF, defined as the identification of a prohibited substance or its metabolite in a doping control sample, is essential for the effectiveness of anti-doping efforts [47].

Locard’s Exchange Principle is a fundamental concept in forensic science, formulated by Dr. Edmond Locard, a French criminologist and pioneer in forensic investigations. It states that “every contact leaves a trace”. This means that whenever two objects or individuals come into contact, there is an exchange of materials between them. Even the smallest traces can serve as crucial evidence in criminal investigations. Therefore, proper testing, decontamination, and protective measures can help reduce the dangers of second-hand methamphetamine exposure. None of these key points were safeguarded.

In conclusion, the landscape of psychoactive substances is rapidly evolving, presenting significant challenges in both clinical and forensic settings. The emergence of new synthetic compounds, the rise of adulterated substances, and the increasing accessibility of these drugs through illicit markets make it essential for professionals to stay informed and adaptable. A critical aspect of this evolving landscape is the risk of accidental exposure, which remains a largely underrecognized issue among policymakers and healthcare providers. Whether through environmental contamination, unintentional ingestion, or cross-contamination in manufacturing and distribution, the dangers of inadvertent exposure can have serious health and legal implications. Addressing this concern will require comprehensive research, improved regulatory measures, and proactive public health strategies to mitigate risks and enhance early detection. Performing confirmatory methods, optimizing sample preparation, and distinguishing between enantiomers, controlling environmental and carryover contamination, documenting chain of custody and analytical traceability, properly training in toxicology and cross-reactivity, and educating athletes and clients on real-world passive exposure risks, such as the proximity to users or contaminated environments, reuse of shared personal items, and travel accommodations in locations with a history of drug use or manufacture are some preventive behavioral measures to taking into account.

The market for and consumption of psychoactive substances are reaching significant value all over the world, with organized criminal groups exploiting instability and gaps in laws and control [48]. The impact is everywhere, with psychiatry-related problems, youth criminality, homelessness, etc. Since psychoactive substances continue to influence public health and safety concerns, scientists, clinicians, law enforcement, and policymakers need to collaborate in creating effective solutions. As Editor-in-Chief, I strongly encourage researchers and scholars to submit their innovative work to our journal, promoting the sharing of impactful clinical and forensic findings. Through collaborative efforts and scholarly exchange, we can advance progress in studying psychoactive substances, assuring that scientific insights guide clinical and forensic practices while fostering safer communities and more effective prevention strategies. Understanding the health impacts and severe long-term physical, mental, and social consequences, developing effective treatments for drug dependence, reducing the high risk of overdose associated with several psychoactive substances, reducing the trafficking and criminal activity associated with addiction, providing critical knowledge for healthcare providers and law enforcement to address emerging threats effectively, and creating awareness on the licit and illicit use of psychoactive substances are the major focuses of Psychoactives. I eagerly anticipate the valuable contributions shaping this vital research area’s future.