Benzodiazepines produce many therapeutic effects, including:
· sedation before anesthesia
· sleep inducement
· relief of anxiety and tension
· skeletal muscle relaxation
· anticonvulsant activity.
Benzodiazepines are used in various clinical situations and exert either a primary or a secondary sedative or hypnotic effect. Ben-zodiazepines used primarily for their sedative or hypnotic effects include:
Benzodiazepines used primarily for the treatment of anxiety in-clude:
Benzodiazepines are absorbed rapidly and completely from the GI tract and are distributed widely in the body. Penetration into the brain also occurs rapidly. Some benzodiazepines, such as diaze-pam and lorazepam, may also be given parenterally.
The duration of effect is determined by the extent of distribution. Triazolam binds quickly to fat and is widely distributed; therefore, it has a short duration of action.
All benzodiazepines are metabolized in the liver and excreted pri-marily in urine. Some benzodiazepines have active metabolites, which may give these drugs a longer period of action.
Researchers believe that benzodiazepines work by stimulating gamma-aminobutyric acid (GABA) receptors in the ascending reticular activating system (RAS) of the brain. The RAS is associ-ated with wakefulness and attention and includes the cerebral cortex and limbic, thalamic, and hypothalamic levels of the cen-tral nervous system (CNS). (See How benzodiazepines work)
At low dosages, benzodiazepines decrease anxiety by acting on the limbic system and other areas of the brain that help regulate emotional activity. The drugs can usually calm or sedate the pa-tient without causing drowsiness.
At higher dosages, benzodiazepines induce sleep, probably be-cause they depress the RAS of the brain.
Benzodiazepines increase total sleep time and reduce the number of awakenings. In most cases, benzodiazepines don’t decrease the time spent in rapid-eye-movement (REM) sleep, the state of sleep in which brain activity resembles the activity it shows when awake; the body’s muscles relax, and the eyes move rapidly. Be-cause benzodiazepines don’t decrease the duration of REM sleep, they have a significant advantage over barbiturates.
During each sleep cycle the sleeping person progresses from stage 1, which is drowsiness, to stages 3 and 4, which are deep-sleep stages. Benzodiazepines reduce the amount of time spent in stages 3 and 4. The decrease in stage 4 sleep is accompanied by a reduction in nightmares.
Clinical indications for benzodiazepines include:
· relaxing the patient during the day of or before surgery
· treating insomnia
· producing I.V. anesthesia
· treating alcohol withdrawal symptoms
· treating anxiety and seizure disorders
· producing skeletal muscle relaxation.
Except for other CNS depressants such as alcohol, few drugs in-teract with benzodiazepines.
When benzodiazepines are taken with other CNS depressants (in-cluding alcohol and anticonvulsants), the result is enhanced seda-tive and CNS depressant effects, including reduced level of con-sciousness, reduced muscle coordination, respiratory depression, and death.
Hormonal contraceptives may reduce the metabolism of fluraze pam hydrochloride, increasing the risk of toxicity.
Triazolam may be affected by inhibitors of the CYP3A system (such as erythromycin and ketoconazole). (See Adverse reactionsto benzodiazepines.)