Drugs of abuse
Psychoactive substances used outside medical care: stimulants, hallucinogens, dissociatives, cannabinoids, inhalants and sedative adulterants.
What they are
A group defined by use, not by chemistry. Each substance acts on a known brain target, and the clinician meets them as acute intoxication, withdrawal, a substance use disorder or a complication such as hyperthermia, psychosis or wounds. Street products are often mixed or adulterated, so the label rarely matches the content. In Colombia the national toxicology guide describes amphetamine-type drugs, «2CB», synthetic cannabinoids and mixtures sold under street names.
Mechanism of action
Stimulants (methamphetamine, MDMA) release dopamine, noradrenaline and serotonin through their transporters. Classic psychedelics (LSD, psilocin) activate serotonin 5-HT2A receptors. Dissociatives (phencyclidine) block NMDA glutamate receptors. Cannabinoids act on CB1 receptors. Inhaled solvents depress the brain much like anaesthetics, and xylazine is an alpha-2 agonist that adds sedation to illicit opioids.
Target: Monoamine transporters, 5-HT2A, NMDA, CB1 and alpha-2 receptors
Drugs in this class
- MDMA (midomafetamine)A synthetic amphetamine («ecstasy») with stimulant and mild psychedelic effects; it floods the brain with serotonin…Monoamine transporters: serotonin transporter (SERT) first, plus VMAT2
- Methamphetamine (metamfetamine)A potent synthetic stimulant with high addiction potential. A prescription form exists for ADHD in some countries…Dopamine and noradrenaline transporters (DAT, NET) and VMAT2; also the receptor TAAR1
- CannabisThe plant Cannabis sativa; its main psychoactive compound, THC, acts on CB1 receptors. Widely used; medical-use…Cannabinoid receptor 1 (CB1); CB2 on immune cells
- Lysergide (LSD)A very potent semi-synthetic psychedelic that activates serotonin 5-HT2A receptors; it alters perception for many…Serotonin 5-HT2A receptor (also other 5-HT and dopamine receptors)
- Phencyclidine (PCP)A dissociative drug («angel dust») that blocks NMDA glutamate receptors; it can cause psychosis, violent agitation…NMDA glutamate receptor channel (pore site shared with ketamine)
- PsilocybinThe psychedelic in «magic mushrooms» (Psilocybe species). The body turns it into psilocin, which activates 5-HT2A…Serotonin 5-HT2A receptor (via its active form, psilocin)
- Inhaled solventsGlues, thinners, fuels and aerosols whose vapours are inhaled, mostly by adolescents. One session can trigger a fatal…NMDA and GABA-A receptors and other ion channels (anaesthetic-like actions)
- Synthetic cannabinoidsLab-made CB1 agonists sprayed on plant material or put in vape liquids («K2», «Spice»). Far stronger than THC and…Cannabinoid receptor 1 (CB1)
- XylazineA veterinary sedative («tranq») mixed into illicit fentanyl and heroin. An alpha-2 agonist, not an opioid: naloxone…Central alpha-2 adrenergic receptors (like clonidine)
- Diamorphine (heroin)Heroin: an opioid made from morphine. A rush, then drowsiness and slowed breathing; overdose kills by respiratory…Mu-opioid receptor (after conversion to morphine)
Others in the class
- Cocaine (stimulant)
- Synthetic cathinones («bath salts»)
- 2C-B and other phenethylamines
- Ketamine (dissociative)
- Alcohol, opioids and sedatives (see their own classes)
Test yourself
Think of the answer, then tap the question to see it.
Which receptor do LSD and psilocin mainly activate?
The serotonin 5-HT2A receptor.
Which drug class is usually first line for stimulant-induced agitation?
Benzodiazepines; antipsychotics lower the seizure threshold and are second line.
Why can an overdose mixed with xylazine fail to respond fully to naloxone?
Xylazine is an alpha-2 agonist, not an opioid, so naloxone does not reverse its sedation.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Guía para el Manejo de Emergencias Toxicológicas (Ministerio de Salud y Protección Social; Organización Panamericana de la Salud, 2017); Drugs A to Z (National Institute on Drug Abuse (NIDA), 2025).
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Representative model, for educational purposes only.