What Is CNS Depression?

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Ask the experts

What is "CNS depression"? This is listed as a side effect from combining two of the medications I take.

Doctor's response

A depressant, by definition, reduces or diminishes a function or activity. A CNS depressant, therefore, would depress the activity of the central nervous system (CNS). Some drugs that are commonly used as sedatives, hypnotics (sleep aids), and anesthetics are CNS depressants. There are numerous CNS depressant drugs; most act on the brain by affecting the neurotransmitter gamma-aminobutyric acid (GABA) to produce a drowsy or calming effect.

Symptoms of CNS depression vary according to the extent to which CNS function is reduced. Symptoms may include:

  • feeling sleepy and uncoordinated,
  • staggering,
  • blurred vision,
  • impaired thinking,
  • slurred speech,
  • impaired perception of time and space,
  • slowed reflexes and breathing, and
  • reduced sensitivity to pain.

Ultimately in severe cases, CNS depression causes unconsciousness and coma. If you are concerned about the possibility of this side effect, your pharmacist or doctor can provide more specific information about the potential and extent of CNS depression that you may experience from combining the two specific medications you're taking.

Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care


What Are CNS Depressants?
National Institute on Drug Abuse

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Reviewed on 6/23/2017