SEDATIVE AND HYPNOTIC AGENTS
1. INTRODUCTION
Sedative and hypnotic agents form an important class of drugs that are widely
used in modern medical practice. The names of many of the agents should be fairly
familiar to you since these drugs are so widely used in hospitals and dispensed to
patients on an outpatient basis. You probably know that most sedative-hypnotic agents
are controlled because of their abuse/misuse potential. The barbiturates have been
regarded as the prototypes of this class of drugs because of their extensive use over
the past 80 years. Because of their potential for addiction, physical dependence, and
side effects, the barbiturates have been replaced by the benzodiazepines (for example,
Valium®). The benzodiazepines are currently the most important sedative hypnotics
because of their efficacy and safety.
2. DEFINITION OF SEDATIVE-HYPNOTIC
A sedative-hypnotic agent is a substance, which, if given in progressively larger
doses, produces calm (sedation), sleep (hypnosis), general anesthesia, and ultimately
death (because of medullary depression). Sedative-hypnotic agents are commonly
used for symptomatic relief of anxiety and for the induction of sleep. Sedatives may be
also referred to as anti-anxiety agents.
Section II. CLINICALLY IMPORTANT INFORMATION
CONCERNING SEDATIVE-HYPNOTICS
3. INTRODUCTION
Sedative-hypnotic agents are an important group of drugs, which are often
prescribed to a variety of patients. You should be familiar with the effects and the
clinical uses of these drugs.
4. THE PHARMACOLOGICAL ACTIONS OF SEDATIVE-HYPNOTIC AGENTS
a. Mechanism of Action. Sedatives and hypnotics selectively depress the
reticular activating system (RAS), the mechanism responsible for keeping us awake
Section III. CLASSIFICATION OF SEDATIVE-HYPNOTIC AGENTS
NOTE: The agents in this section are classified according to their duration of action
and whether they are barbiturates or nonbarbiturates.
8. BARBITURATE SEDATIVES AND HYPNOTICS
a.Ultra Short-Acting Barbiturates.
(1) Basic information. Ultra short-acting barbiturates usually have a duration
of action of 15 to 30 minutes. They are administered intravenously in order to induce
anesthesia because of their high degree in lipid (fatty) materials. Ultra short-acting
barbiturates are used to counter act the convulsions associated with some chemical
substances (for example, tetanus toxin) or by the overdosage of certain drugs.
(2)
Examples of ultra short-acting barbiturates.
(a) Methohexital (Brevital®).
(b) Thiopental (Pentothal®).
b. Short-Acting Barbiturates.
(1) Basic information. Short-acting barbiturates usually have a duration of
action that lasts from 2 hours to 4 hours. Short-acting barbiturates are effective
treatment--when taken by mouth--for the initial and short-term treatment of insomnia.
These agents are widely used intramuscularly (IM) for preanesthetic sedation in order to
calm the patient and to reduce anxiety often found in patients about to undergo surgery.
Pentobarbital and secobarbital (see below) may be used for short-term daytime
sedation in patients who suffer from anxiety.
(2)
Examples of short-acting barbiturates.
- Pentobarbital (Nembutal®).
- Secobarbital (Seconal®
c.
Intermediate-Acting Barbiturates.
(1) Basic information. Intermediate-acting barbiturates have a duration of
action that lasts from 4 hours to 6 hours. These agents are mainly use for the initial and
short-term treatment of insomnia.
Example of intermediate-acting barbiturate. Amobarbital (Amytal®).
(2)
d Long-Acting Barbiturates.
(1) Basic information. Long-acting barbiturates have a duration of action
that lasts from 6 hours to 8 hours. These agents are used orally to maintain daylong
sedation in anxiety-tension states. Furthermore, long-acting barbiturates are useful in
the treatment of various convulsive disorders.
(2)Examples of long-acting barbiturates.
- Phenobarbital.
- Mephobarbital (Mebaral®).
9. NONBARBITURATE SEDATIVES AND HYPNOTICS
a.Short-Acting Agents.
(1) Background information. Short-acting nonbarbiturate sedative-hypnotics
are generally used orally in the initial and short-term treatment of insomnia.
(2)
Examples of short-acting nonbarbiturate sedative-hypnotics.
(a) Chloral hydrate (Noctec®). Drug interactions may occur between
chloral hydrate and anticoagulants, furosemide, alcohol, or other drugs that are CNS
depressants.
(b) Triazolam (Halcion®). Triazolam is rapidly absorbed through the
oral route and is as effective as the barbiturates in inducing sleep. It is excreted in
breast milk and should not be administered to nursing mothers.
b.
Intermediate-Acting Agents.
(1) Background information. Intermediate-acting nonbarbiturate agents are
administered orally to effectively control moderate to severe daytime anxiety and
tension in patients who have neuroses and mild depressive states.
(2)
Examples of intermediate-acting nonbarbiturates
(a) Diazepam (Valium®). Diazepam may be useful in the treatment of
alcohol withdrawal symptoms (for example, delirium tremens, agitation, and so forth.)
This agent produces skeletal muscle relaxant effects in humans and has been used with
limited success in various neurologic and musculoskeletal disorders. Diazepam may be
administered parenterally as a preanesthetic medication to reduce anxiety and to calm
the patient. Diazepam is also administered intravenously in the treatment of status
epilepticus. It is available in tablet form (2, 5, and 10 milligrams) and in injection form
(5 milligrams per milliliter in 2 and 10 milliliter containers). Diazepam is a Note Q
controlled substance in the military.
(b) Meprobamate (Equanil®, Miltown®). Meprobamate can produce
skeletal muscle relaxant effects in humans; therefore, it has been used with some
success in the treatment of various neurologic and musculoskeletal disorders. It
appears to be less effective than diazepam in the treatment of anxiety and tension. The
most common side effect associated with the agent is drowsiness. It is supplied in
tablet and suspension forms. Meprobamate is a Note Q controlled item in the military.
(c) Other examples of nonbarbiturates used in the treatment of anxiety
disorders include Lorazepam (Ativan®), Alprazolam (Xanax®), and Buspirone (Buspar®).
Lorazepam is used primarily as an antianxiety agent, but is useful for treating insomnia
due to stress and anxiety. Lorazepam is also used as a preanesthetic medication to
produce sedation and decrease the patient's ability to recall events related to the day of
surgery.
(d) Temazepam (Restoril®). Temazepam is administered in a nightly
dose of 15 to 30 mg. It is an effective inducer of sleep with a good safety profile.
Animal studies indicate a potential for Temazepam to cause teratogenic effects.
Therefore, it should not be administered during pregnancy.
c.
Long-Acting Nonbarbiturate Agents.
(1) Background information. These agents depress the central nervous
system. Patients taking these drugs should be cautioned against performing hazardous
activities while under their effects.
(2)
Examples of long-acting nonbarbiturate agents.
(a) Chlordiazepoxide hydrochloride (Librium®). Chlordiazepoxide is
orally administered as an antianxiety agent. It is also effective when administered
parenterally in the treatment of alcohol withdrawal. Side effects associated with the
agent include drowsiness, ataxia, and lethargy.
(b) Oxazepam (Serax®). Oxazepam is generally less effective than
either diazepam or chlordiazepoxide in the treatment of tension and anxiety.
Drowsiness is the most common side effect associated with this agent.
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