Anxiolytic Drugs

Anxiolytic medications reduce symptoms of anxiety. Hypnotic drugs induce sleep. Both medications can function in either role and are sometimes known as "minor tranquilizers" (to distinguish them from the "major tranquilizers," barbiturates and antipsy-chotics). Anxiolytics and hypnotics are among the most frequently prescribed medications and have a wide application, including long-term treatment of anxiety disorders, relaxation and sedation before procedures, treatment of acute agitation, and medically managed withdrawal from substances. Despite valid and effective applications in medical practice, almost every drug in this class has significant potential for abuse and dependence with long-term use. This entry reviews the different classes of medications used to treat anxiety and insomnia with an emphasis on the benzodiazepines (BZDs).

Anxiolytics offer predictable, short-term relief from anxiety symptoms related to situational anxiety or a psychiatric disorder. Anxiety is an uncomfortable state of brain overactivity with both emotional symptoms (worry, dread) and physical symptoms (increased muscle tone, increased heart rate, difficulty falling asleep). Normal life events such as public speaking, examinations, or a turbulent flight can cause anxiety. Some people develop anxiety disorders, with abnormally elevated or persistent anxiety that affects their daily functioning. The most common anxiety disorders are phobias, panic disorder, generalized anxiety disorder, post-traumatic stress disorder, and obsessive-compulsive disorder. Anxiety symptoms can also be present as part of another psychiatric disorder, such as major depression or psychosis.

Anxiolytics work by decreasing brain excitability. The primary inhibitory neurotransmitter in the brain is gamma-aminobutyric acid (GABA), which acts on chloride channels on brain cell membranes. BZDs effectively enhance GABA activity at the receptor level by increasing the frequency of chloride channel openings, decreasing the resting tone and subsequent activity level of brain cells. A mild decrease in brain resting tone can induce a state of relaxation. Larger decreases lead to sleep induction.

Newer anxiolytics target different receptors. Buspirone, for example, acts upon serotonin receptors and, in contrast to the fast-acting BZDs, can take 4 to 6 weeks for full effect. The major classes of anxiolytics are presented in this entry, along with the representative drugs, their side effects, overdose potential, and role in substance use disorders. Selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, and other antidepressants treat anxiety disorders over longer periods but have a different mechanism of action and are not classified primarily as anxiolytics.