Driving a car is one of the most complex activities humans perform. It requires attention, reflexes, and the ability to make decisions within fractions of a second. Meanwhile, an increasing number of drivers are on the road under the influence of substances, which—although legal in the context of treatment—may lead to slowed reactions, concentration problems, and impaired motor coordination.
A team of researchers from Wroclaw Medical University analyzed the results of more than 30 scientific studies concerning the impact of 2-phenylethylamine (PEA) derivatives and opioids on psychomotor functions and the ability to drive. The findings were published in Pharmaceuticals as part of a systematic review.
The difference between therapy and risk
The researchers emphasize that substances such as methylphenidate, used in ADHD therapy, can, in small doses, improve concentration and reaction time, thereby increasing road safety. Under controlled treatment conditions, they help patients react more quickly, maintain lane position, and more precisely control speed.
However, the line between a therapeutic effect and risk is thin. At higher or uncontrolled doses, these same substances may lead to excessive self-confidence, impulsivity, and impaired coordination—factors that increase the likelihood of an accident.
Opioids – they relieve pain but slow reactions
The situation looks different for opioids such as methadone, tramadol, or fentanyl. Their analgesic effects are often accompanied by drowsiness, slowed reactions, and impaired visuomotor coordination. Studies have shown that drivers taking methadone or tramadol are more prone to road accidents. An exception includes patients treated chronically with low doses of fentanyl in patch form—due to developed tolerance, the impact on psychomotor performance is minimal.
The analyzed substances also included psychoactive agents used recreationally—MDMA (ecstasy) or methamphetamine. Although they may transiently increase alertness, the effect is deceptive. Most studies point to impaired vehicle control, unstable speed, and greater risk-taking behavior.
When pharmacology meets the law
The authors remind readers that under Polish law, any substance that affects the central nervous system and may reduce the ability to drive is considered an “intoxicant”—regardless of whether it is a prescription medication or a narcotic. A driver who is aware of a drug’s effects is fully responsible for the consequences of driving after taking it.
“It should be emphasized that when prescribing a medication with potential impact on road safety, the physician is obliged to inform the patient about this risk in advance. Each traffic accident is evaluated individually by the courts. An appropriate note in the medical documentation may be crucial in legal proceedings, protecting the physician from criminal liability.”, notes Kacper Żełabowski, Chair of the Scientific Society for Psychopharmacology, Department of Forensic Medicine, Wroclaw Medical University.
What’s next?
The results of the review indicate that the impact of psychoactive substances on road safety depends on the dose, timing, health status, and driving experience of the individual. Therefore, the researchers call for the development of precise clinical and legal guidelines that would enable physicians to better inform patients about potential risks.
Understanding the mechanisms of action of these substances—both at the biochemical and behavioral levels—may in the future help create safer treatment schemes and reduce the number of accidents caused by drivers “under the influence of medication.”
This material is based on the article:
Review of Selected 2-Phenylethylamine Derivatives and Opioids, Systematic Review of Their Effects on Psychomotor Abilities and Driving Performance: Psychopharmacology in the Context of Road Safety
Kacper Żełabowski, Kamil Biedka, Wojciech Pichowicz, Maria Sterkowicz, Izabela Radzka, Ignacy Ilski, Michał Wesołowski, Kacper Wojtysiak, Wiktor Petrov, Dawid Ślebioda, Maciej Rząca, Agnieszka Chłopaś-Konowałek
Pharmaceuticals 2025, 18(10), 1555;
https://doi.org/10.3390/ph18101555