AbstractRecreational substance use is becoming more common, especially among young people. Some anti-inflammatory or antitussive drugs exert potent psychoactive effects when they are used in large doses. Easily available over-the-counter (OTC) drugs may cause a range of effects including hallucinations or euphoria.Dextromethorphan (DXM) is particularly often used. At doses of 1.5–7.5mg/kg body mass it induces stimulation, mood improvement, motor impairment, and used at doses higher than 7.5mg/kg b.m., it exerts dissociative effects. Adverse reactions are especially clear when DXM was taken with alcohol or substances affecting metabolic activity of cytochrome P450 CYP2D6. Among DXM users, some cases of psychological dependence and withdrawal...