Sedative-Hypnotic and Anxiolytic Drugs

Sedative-Hypnotic and Anxiolytic Drugs


Sedative-hypnotic drugs are among the most widely used pharmaceutical agents in the world. The sedative part of their name refers to the ability of these agents to calm or reduce anxiety, known as an anxiolytic effect. The hypnotic part of their name describes the ability of these agents to induce drowsiness and promote sleep. This latter action is caused by a greater depression of central nervous system (CNS) activity; most sedative-hypnotic drugs will first cause sedation, then at higher doses produce hypnosis, the medical term for sleep. A few agents, however, exert anxiolytic effects without causing sedation or hypnosis.

This chapter describes the pharmacologic properties of benzodiazepines, barbiturates, and other sedative-hypnotic and anxiolytic drugs that are used in the treatment of anxiety and sleep disorders. Because of their greater safety, fewer adverse effects, and the availability of an antagonist, the benzodiazepines have largely replaced the older barbiturates for these indications. Although ethanol (alcohol) has sedative-hypnotic effects, it is not used therapeutically for these purposes; its pharmacologic effects are described in Chapter 25.

Anxiety Disorders

Anxiety is normally an adaptive response that prepares a person to react to the challenges of life. Anxiety is characterized by changes in mood (apprehension and fear), sympathetic nervous system arousal, and hypervigilance. When anxiety becomes chronic, it can impair a person’s ability to perform the activities of daily living. Moreover, chronic anxiety often leads to visceral organ dysfunction and unpleasant symptoms. For example, patients with chronic anxiety may develop gastrointestinal, cardiovascular, and neurologic problems, including diarrhea, tachycardia, sweating, tremors, and dizziness. Ultimately, anxiety can contribute to heart disease and other disorders, including self-medication, which may lead to substance abuse.

Neurologic Basis of Anxiety

The neuronal pathways involved in anxiety disorders include the sensory, cognitive, behavioral, motor, and autonomic pathways. Sensory systems, cortical processing, and memory are involved in interpreting a stimulus to be dangerous and creating a state of heightened arousal. Motor systems and autonomic processing participate in the exaggerated responses to an anxiety state.

Growing evidence indicates that the amygdala, an almond-shaped structure in the temporal lobe, plays a central role in mediating most of the manifestations of anxiety, including the conditioned avoidance reaction (conditioned fear reaction) that underlies anxiety states. In experimental protocols, this reaction can be induced in animals by teaching them that a cue (e.g., a flashing light) will be followed by a noxious stimulus (e.g., a shock to the foot). During the anticipatory period, the animals conditioned in this manner will exhibit signs of anxiety, such as autonomic and behavioral arousal. Electrical stimulation of the amygdala induces signs of anxiety, whereas lesioning the amygdala or the administration of anxiolytic drugs prevents the behavioral and physiologic manifestations of anxiety during the anticipatory period. It is believed that long-term potentiation in amygdala neurons establishes the memory of adverse events underlying anticipatory anxiety.

Classification and Treatment of Anxiety Disorders

The appropriate management of anxiety disorders requires an accurate diagnosis, and treatment may involve the use of pharmacologic agents, psychotherapy, or both.

Phobic Disorders

Phobic disorders can be grouped into specific phobia, social anxiety disorder (social phobia), or agoraphobia. Phobias are conditions in which an individual is overly fearful about a particular situation or condition, such as a fear of spiders or traveling in an airplane. Panic disorder can coexist with agoraphobia, an intense fear of being in a public place from which it might be difficult or embarrassing to cope with a panic attack. Patients with panic disorder and agoraphobia often show the best outcomes when treated with a combination of psychotherapy and drug therapy. As with panic disorder, phobic disorders are treated with a benzodiazepine or an antidepressant drug. Benzodiazepines provide acute relief of symptoms and enable patients to more easily benefit from psychotherapy, whereas antidepressants are usually the most effective long-term drug therapy for agoraphobia and social phobia. Propranolol is useful in the prevention of stage fright, or acute situational or performance anxiety.

Generalized Anxiety Disorder

Generalized anxiety disorder (GAD) is characterized by chronic worry and apprehension concerning future events. Short-term therapy with a benzodiazepine may relieve acute symptoms and provide a useful bridge to psychotherapy. The severity of the disorder often fluctuates over time, and benzodiazepines may be effectively used on an intermittent basis to help patients deal with exacerbations of the disorder. Buspirone, a nonsedating anxiolytic, provides a useful alternative to benzodiazepines for the treatment of chronic anxiety states, because it produces little sedation and is not associated with tolerance or dependence. It must be taken for 3 or 4 weeks, however, before its anxiolytic effects are felt. SSRIs, such as paroxetine, and the serotonin and norepinephrine reuptake inhibitors (SNRIs) venlafaxine and duloxetine (see Chapter 22), are also used in the treatment of GAD.

Sleep Disorders

Sleep is a reversible state of reduced consciousness that is accompanied by characteristic changes in the EEG. Five distinct patterns of brainwave activity occur during sleep, grouped into the four stages of non-rapid eye movement (NREM) sleep, and a pattern characterized by paralysis of voluntary muscles and quick, saccadic movement of the eye called rapid eye movement (REM) sleep.

As an individual falls asleep, the high-frequency and low-amplitude activity of the alert state gradually diminishes during stages 1 and 2 and is replaced by the low-frequency and high-amplitude activity of slow-wave sleep (stages 3 and 4). Over time, the individual returns to stage 1 and eventually to the REM stage. REM sleep is also known as paradoxical sleep because the EEG pattern is similar to that in the awake state. A normal adult cycles through the sleep stages about every 90 minutes (Box 19-1).

Box 19-1   Effect of Sedative-Hypnotic Drugs on Sleep Architecture Terminology

Patterns on the electroencephalogram (EEG) vary with the stage of sleep. When a person falls asleep, the high-frequency and low-amplitude pattern of the awake state is gradually replaced by the progressively lower-frequency and higher-amplitude patterns of stages 1 through 4, which collectively are called non–rapid eye movement sleep (NREM sleep). Stages 3 and 4 are called slow-wave sleep. Another stage, called rapid eye movement sleep (REM sleep), is characterized by rapid, jerky eye movements. REM sleep is also called paradoxical sleep because it is during this stage that the pattern on the EEG returns to the pattern seen during the awake state.

Effects of Drugs on Sleep Architecture

The sleep patterns of patients with insomnia vary widely but are often characterized by reduced amounts of slow-wave sleep and by one or more awakenings during the night. The time required to fall asleep (sleep latency) is usually prolonged, and the total sleep time is decreased in most patients with insomnia. Elderly adults often have a similar sleep pattern.


Benzodiazepines and most other hypnotics suppress stage 3 and REM sleep. In contrast, zolpidem, zaleplon, eszopiclone, and ramelteon (new agents) have little effect on sleep architecture. Therefore the use of these new agents may better restore the sleep pattern to normal.

State Rapid Eye Movements Pattern on EEG Effect of Benzodiazepines Effect of New Agent
Awake No High-frequency, low-amplitude pattern Induce sleep Induces sleep
Stages 1 and 2 sleep No Lower-frequency, higher-amplitude pattern than awake state Increase length of stages Little change
Stages 3 and 4 sleep No Lower-frequency, higher-amplitude pattern than stages 1 and 2 Decrease length of stages Little change
REM sleep Yes High-frequency, low-amplitude pattern Decrease length of stage Little change


Sleep patterns change with age and are altered by sedative-hypnotic and other CNS drugs.

Classification and Treatment of Sleep Disorders


Some patients with insomnia find it difficult to go to sleep or to stay asleep during the night, whereas others awaken too early in the morning. In general, the management of insomnia depends on whether the sleep disorder is caused by physiologic, psychological, or medical conditions. As shown in Box 19-1, the patterns of sleep stages in patients with insomnia are irregular and include longer latency to fall asleep and frequent awakenings.

Occasional sleeplessness caused by acute stress or a minor illness is usually self-limiting and may not require treatment. More severe insomnia caused by medical conditions whose symptoms interfere with sleep is effectively treated with benzodiazepines or other sedative-hypnotic drugs, such as zolpidem and zaleplon, whereas insomnia related to psychological and psychiatric disturbances is best managed with a combination of psychotherapy and sedative-hypnotic drugs. Benzodiazepines and most other hypnotic drugs decrease sleep latency (the time required to go to sleep) and increase sleep duration. The newest agents, zolpidem, zaleplon, eszopiclone, and ramelteon, have the advantages of not significantly affecting sleep architecture and not causing as much tolerance and dependence as do the older drugs. For these reasons, zolpidem, zaleplon, eszopiclone, and ramelteon have become the drugs of choice to treat most types of insomnia.

Sedative-Hypnotic Drugs

The sedative-hypnotic drugs include benzodiazepines, barbiturates, some antihistamines, and a few nonbenzodiazepine agents, such as zolpidem, zaleplon, eszopiclone, and ramelteon. The properties of these drugs are summarized in Table 19-1, and their adverse effects and drug interactions are listed in Table 19-2.

TABLE 19-1

Pharmacokinetic Properties and Clinical Uses of Sedative-Hypnotic and Anxiolytic Drugs

Alprazolam Fast Medium Yes Anxiety, including panic disorder
Chlordiazepoxide Fast; very fast (IV) Long Yes Alcohol detoxification; anxiety
Clonazepam Fast Medium No Anxiety, including panic disorder; seizure disorders
Diazepam Fast; very fast (IV) Long Yes Alcohol detoxification; anxiety; muscle spasm; seizure disorders; spasticity
Estazolam Fast Medium Yes Insomnia
Flurazepam Fast Long Yes Insomnia
Lorazepam Fast; very fast (IV) Medium No Anxiety; seizure disorders
Midazolam Very fast (IV) Short (IV) Yes Anesthesia
Oxazepam Fast Short No Anxiety
Temazepam Fast Medium No Insomnia
Triazolam Fast Short Yes Insomnia
Amobarbital Fast Medium No Insomnia
Pentobarbital Fast Short No Insomnia
Phenobarbital Slow Long No Seizure disorders
Thiopental Very fast (IV) Short (IV) No Induction of anesthesia
Diphenhydramine Fast Medium No Insomnia
Hydroxyzine Fast Long No Anxiety; sedation
Other Sedative-Hypnotic Drugs    
Zolpidem Fast Short No Insomnia
Zaleplon Fast Very short No Insomnia; midsleep awakenings
Eszopiclone Fast Short No Insomnia
Ramelteon Slow Short Yes Sleep-onset insomnia
Nonsedating Anxiolytic Drugs    
Buspirone Very slow Long No Chronic anxiety
Propranolol Fast Medium Yes Situational or performance anxiety
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Jul 23, 2016 | Posted by in PHARMACY | Comments Off on Sedative-Hypnotic and Anxiolytic Drugs

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