CNS depression
CNS depression refers to physiological depression of the central nervous system, for example in propoxyphene poisoning.

# CNS depressants
What are CNS depressants?
CNS depressants, sometimes referred to as sedatives and tranquilizers, are substances that can slow normal brain function. Because of this property, some CNS depressants are useful in the treatment of anxiety and sleep disorders. Among the medications that are commonly prescribed for these purposes are the following:
Barbiturates, such as mephobarbital (Mebaral) and pentobarbital sodium (Nembutal), are used to treat anxiety, tension, and sleep disorders.
Benzodiazepines, such as diazepam (Valium), chlordiazepoxide HCl (Librium), and alprazolam (Xanax), are prescribed to treat anxiety, acute stress reactions, and panic attacks. The more sedating benzodiazepines, such as triazolam (Halcion) and estazolam (ProSom) are prescribed for short-term treatment of sleep disorders. Usually, benzodiazepines are not prescribed for long-term use.
How do CNS depressants affect the brain and body?
There are numerous CNS depressants; most act on the brain by affecting the neurotransmitter gammaaminobutyric acid (GABA). Neurotransmitters are brain chemicals that facilitate communication between brain cells. GABA works by decreasing brain activity. Although the different classes of CNS depressants work in unique ways, it is through their ability to increase GABA activity that they produce a drowsy or calming effect that is beneficial to those suffering from anxiety or sleep disorders.
What are the possible consequences of CNS depressant use and abuse?
Despite their many beneficial effects, barbiturates and benzodiazepines have the potential for abuse and should be used only as prescribed. During the first few days of taking a prescribed CNS depressant, a person usually feels sleepy and uncoordinated, but as the body becomes accustomed to the effects of the drug, these feelings begin to disappear. If one uses these drugs long term, the body will develop tolerance for the drugs, and larger doses will be needed to achieve the same initial effects. Continued use can lead to physical dependence and - when use is reduced or stopped - withdrawal. Because all CNS depressants work by slowing the brain's activity, when an individual stops taking them, the brain's activity can rebound and race out of control, potentially leading to seizures and other harmful consequences. Although withdrawal from benzodiazepines can be problematic, it is rarely life threatening, whereas withdrawal from prolonged use of other CNS depressants can have life-threatening complications. Therefore, someone who is thinking about discontinuing CNS depressant therapy or who is suffering withdrawal from a CNS depressant should speak with a physician or seek medical treatment.
Is it safe to use CNS depressants with other medications?
CNS depressants should be used in combination with other medications only under a physician's close supervision. Typically, they should not be combined with any other medication or substance that causes CNS depression, including prescription pain medicines, some OTC cold and allergy medications, and alcohol. Using CNS depressants with these other substances - particularly alcohol - can slow both the heart and respiration and may lead to death.1
1 NIDA: National Institute on Drug Abuse, The Science of Drug Abuse and Addiction
Research Report Series - Prescription Drugs: Abuse and Addiction.