Depressant

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

A depressant, referred to in slang as a "downer," is a chemical agent that diminishes the function or activity of a specific part of the body (see also sedative). The term is especially used with regard to the central nervous system (CNS). Alcohol (consumed in alcoholic beverages) is the most obvious example of a depressant. Although some drugs act on the CNS by targeting or involving receptors such as the NMDA receptor, the mu-opioid receptor, and the CB1 cannabinoid receptor, many depressants impact the CNS by increasing the activity of a particular neurotransmitter known as gamma-aminobutyric acid (GABA),

GABA's role is to calm the CNS and promote sleep. Drugs that stimulate the activity of this amino acid slow brain function and result in a drowsy or calm feeling. These characteristics account for the prescription of depressants to relieve symptoms of anxiety or insomnia. Internal systems regulate the body's production of GABA, but when substances that stimulate GABA action are ingested, it is possible to induce hazardously high levels of the amino acid, which can slow breathing and heart rates dangerously, and may result in death.

CNS depressants require a period of adaptation. Typically, initial side effects include slurred speech, dizziness, and loss of coordination, effects commonly associated with alcohol consumption.

Medical Uses

The most common medically used depressants generally fall into two classes, namely barbiturates and benzodiazepines. Other depressants include alcohol, narcotics (opiate derivatives), sedative-hypnotics, first-generation antihistamines (such as diphenhydramine,) and some anaesthetics (such as ketamine and phencyclidine).

Barbituates
While barbiturates are effective in relieving the conditions they are designed to address, they are readily abused, physically addictive, and have serious potential for overdose. In the late 1960s, when it became clear that the social cost of barbiturates was beginning to outweigh their medical benefits, a serious search began for a replacement drug (see Methaqualone). Most people still using barbiturates today do so to prevent seizures or use mild forms to relieve the symptoms of migraines.

Benzodiazepines
Benzodiazepines mediate many of the same symptoms as barbiturates, but are far less toxic and have a greatly reduced risk of overdose. However, benzodiazepines carry their own risks; where barbiturates pose a greater "front-end" danger in that overdose or drug/alcohol interactions may result in fatality, benzodiazepines pose a greater "back-end" risk with their higher potential for addiction, dependence, and serious physical and psychological withdrawal symptoms. Sudden cessation of long-term benzodiazepine use instead of tapering can be dangerous and have serious results.

Combining multiple depressants is very dangerous as CNS-depressive properties often increase multiplicatively rather than linearly. This characteristic makes depressants a common choice for deliberate overdoses (in the case of suicide). In the case of those addicted to opiates, the ingestion of alcohol or benzodizepines along with a normal dose of heroin (average daily dose of 300-500 mg) often results in death.

Depressants/Downers

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