General pathology · Environmental pathology
Drugs of abuse: cocaine, opioids, amphetamines, cannabis !
- Topic
Drugs of abuse injure the heart, brain, lungs and other organs through their action on neurotransmitters and through the way they are used.
Updated 2026-11-01
What it is
Each drug has its own main target. Stimulants such as cocaine and amphetamines flood synapses with catecholamines and constrict vessels; opioids depress breathing; cannabis acts on cannabinoid receptors. Injecting, snorting or smoking adds infections, burns and airway injury, and use in pregnancy harms the newborn.
Step by step
- Cocaine blocks the reuptake of noradrenaline, dopamine and serotonin; amphetamines release them.
- Excess catecholamines raise heart rate and blood pressure and constrict coronary and cerebral arteries.
- Vasospasm, faster atherosclerosis and thrombosis cause myocardial infarction and stroke, even in young people.
- Sudden surges of blood pressure can tear the aorta or rupture brain vessels.
- Opioids act on mu receptors in the brainstem: breathing slows, the brain becomes hypoxic and the lungs fill with fluid.
- Unsterile injection brings Staphylococcus aureus to the right-sided heart valves and spreads HIV and hepatitis C.
What each drug does to tissue
| Drug | Main action | Typical injury |
|---|---|---|
| Cocaine | Blocks catecholamine reuptake; local vasoconstriction | Infarction, stroke, aortic dissection, arrhythmia, nasal septum perforation, placental abruption |
| Amphetamines and methamphetamine | Releases catecholamines | Hypertension, cardiomyopathy, psychosis, severe dental decay; MDMA: hyperthermia and hyponatraemia |
| Opioids (heroin, fentanyl) | Mu-receptor agonism | Respiratory depression, pulmonary oedema, endocarditis, skin abscesses, neonatal abstinence |
| Cannabis | CB1 receptor agonism (THC) | Cyclic vomiting (hyperemesis), psychosis in vulnerable youth, airway irritation when smoked |
Clinical notes
- Chest pain in a young adult without risk factors raises the question of cocaine use.
- Opioid overdose: coma, pinpoint pupils and slow breathing; naloxone reverses it quickly.
- Stimulant toxicity may cause hyperthermia, rhabdomyolysis and kidney injury.
Test yourself
Think of the answer, then tap the question to see it.
How does cocaine cause myocardial infarction in a young person?
It blocks catecholamine reuptake: coronary vasospasm, higher oxygen demand, platelet activation and thrombosis.
Which heart valve is most often infected in people who inject drugs?
The tricuspid valve, most often by Staphylococcus aureus from the skin, with septic emboli to the lungs.
What are the three classic signs of opioid overdose?
Depressed consciousness, pinpoint pupils and slow, shallow breathing.
Which local lesion is typical of repeated snorting of cocaine?
Ischaemic necrosis and perforation of the nasal septum from repeated vasoconstriction.
Related
- Tobacco: how smoking injures tissue
- Alcohol: how it injures the liver, brain, heart and fetus
- Infarction: red vs white, and what decides the damage
Related conditions
- Cocaine and sympathomimetic toxicity
- Opioid overdose
- Stimulant use disorder (cocaine, amphetamines)
- Opioid use disorder, overdose and withdrawal
- Cannabis toxicity and cannabinoid hyperemesis syndrome
- Cannabis use disorder
- Hallucinogen and dissociative drug intoxication (LSD, PCP, ketamine)
- Infective endocarditis
- Myocardial Infarction (Heart Attack)
- Aortic dissection
- Intracerebral haemorrhage
- Placental abruption
- Neonatal abstinence syndrome
- Rhabdomyolysis
- Serotonin syndrome
Elsewhere in DurgiPedia
Microorganisms
In Pharmacology
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Cocaine intoxication: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Opioids and Opioid Use Disorder (OUD): MedlinePlus (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.