Sedatives and Hypnotics

Psychoactive Drugs

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Psychoactive drugs are a class of chemical substances that act on the central nervous system and can alter behavior and cognition. All psychoactive drugs are highly fat-soluble and thus cross the blood-brain barrier readily. Psychoactive drugs alter synaptic transmission by altering neuro-transmitter amounts and availability or by affecting receptor activity. In addition to the drug's primary effects on behaviors such as arousal, thought processes, mood, perception, and consciousness, psychoactive drugs can produce a variety of nonbehavioral effects that may more directly affect health and, in some instances, can lead to death.

Although there are several different classification schemes for psychoactive drugs (pharmacological, legal, medical), the most common organization is based on their effect on behavior and cognition. According to this scheme, psychoactive drugs can be classified into four broad categories: (1) sedatives and hypnotics, (2) stimulants, (3) opiates, and (4) hallucinogens and psychedelics.

Sedatives and Hypnotics

Sedatives and hypnotics depress or inhibit brain activity and produce drowsiness, sedation, or sleep; relieve anxiety; and lower inhibition. Although the depressant compounds do not share a common neural mechanism of action, most of them either decrease the metabolic activity in the brain or increase the transmission of the principal inhibitory neurotransmitter of the brain, gamma-aminobutyric acid (GABA).

All sedatives have the potential for addiction and dependency. Common depressants include barbiturates, such as Seconal; benzodiazepines, such as Xanax and Valium (commonly called minor tranquilizers); nonbarbiturate sedatives, such as methaqualone; newer nonbenzodiazepines, such as buspirone, antihistamines, and anesthetics; and alcohol. In low doses, alcohol can act as a stimulant; however, with increased dosage alcohol's main effect is depressive.

Stimulants

Stimulants produce behavioral arousal. As with the sedatives and hypnotics, there are a variety of substances, each with a different neural mechanism of action. Examples of stimulants are amphetamine, cocaine, antidepressants, caffeine (the most widely used psychoactive drug in the world), nicotine or tobacco, appetite suppressants, and a variety of exotic plant products. Stimulants vary in strength, legal status, and the manner in which they are taken; however, all stimulants have addictive potential.

The milky juice of unripe seed pods is used to make opium from the opium poppy plant.

Opiates

All drugs in the opiate class act on opiate receptors in the brain. They mediate relief from pain and produce feelings of euphoria. Opiates, which are referred to as narcotics by scientists and medical practitioners, are highly addictive and can either be natural, semisynthetic, or synthetic. Natural opiates such as opium are derived from the opium poppy. The active ingredients of opium are morphine and codeine. The most common semisynthetic opiate is heroin, which is five to ten times more potent than morphine. Examples of synthetic opiates include methadone and the prescription pain medication Demerol.

Дата добавления: 2015-10-23