Types of medicine
What Is a CNS Depressant? Why Labels Warn About Mixing
CNS depressant · say it: see-en-ESS dee-PRESS-untAlso written: central nervous system depressant, CNS depressants, sedative, CNS Depressants, central nervous system depressants, sedatives
Short answer
A CNS depressant is any medicine or substance that slows down brain and nerve activity, causing drowsiness, relaxation or slower breathing.
What it means
CNS stands for central nervous system, which means the brain and spinal cord. A CNS depressant slows down activity there. Examples include alcohol, opioid pain medicines, benzodiazepines, many sleep medicines, some antihistamines and some seizure medicines.
Labels warn about CNS depressants mainly because their effects add up. Taking two or more together, or drinking alcohol with one, can cause deep sleepiness, confusion, falls and, in serious cases, dangerously slow breathing. Very slow or shallow breathing, or being hard to wake, needs emergency help.
'Depressant' here has nothing to do with depression the mood condition. It simply means 'slows down'. A medicine can be a CNS depressant without affecting mood at all.
Where you may see it
- 'Warnings' and 'Drug interactions' sections of opioid, benzodiazepine and sleep medicine labels
- Over-the-counter sleep aid and allergy medicine labels ('alcohol, sedatives and tranquilizers may increase drowsiness')
- Pharmacy warning stickers about alcohol and driving
📄 How it looks on a report
Concomitant use with other CNS depressants, including alcohol, may increase the risk of profound sedation and respiratory depression.
🙅 What it does not mean
- 'Depressant' does not mean the medicine causes depression.
- It does not mean you can never take two such medicines; sometimes doctors combine them carefully, but they need to know about all of them.
- Feeling fine after one dose does not mean the combination is harmless every time.
🎯 Check yourself
Which of these is the right meaning of “CNS depressant”?
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “CNS depressant”
Plain-English explanations of each medicine, from its official FDA label.
- Allopurinol
a xanthine oxidase inhibitor, a prescription medicine that acts on uric acid
- Alprazolam
a benzodiazepine, a type of central nervous system medicine
- Amitriptyline
An antidepressant of the tricyclic type
- Cetirizine
an antihistamine of the selective H1-receptor antagonist type
- Clonazepam
a benzodiazepine, a type of medicine that slows activity in the central nervous system
- Diazepam
A benzodiazepine, a type of medicine that slows activity in the central nervous system (brain and spinal cord)
- Diphenhydramine Hydrochloride
an antihistamine (an antihistaminic agent) given by injection into a vein or deep into a muscle
- Gabapentin
An antiepileptic (seizure) medicine. The label also describes it as a treatment for nerve pain after shingles.
- Lorazepam
A benzodiazepine, a type of anxiety medicine
- Metoclopramide
A stomach and gut medicine. The label describes it as affecting how the stomach and intestines move. The label does not give an FDA drug class.
🔗 Read more from trusted sources
- “CNS depressant” on MedlinePlus ↗
US National Library of Medicine
- NCI Dictionary definition ↗
US National Cancer Institute: “cns depressant”
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