Benzodiazepines
The four benzodiazepine
drugs that provide anticonvulsant ef-fects are:
clonazepam
·
clorazepate
·
diazepam (parenteral form)
·
lorazepam. (See Sound-alikes:
Diazepam and lorazepam.)
Only clonazepam is recommended for long-term
treatment of epilepsy. Diazepam may be used to treat status epilepticus or, in
rectal form, repetitive seizures. Lorazepam I.V. is considered the drug of
choice for status epilepticus. Clorazepate is prescribed as an adjunct in
treating partial seizures.
The patient can receive benzodiazepines orally,
parenterally or, in special situations, rectally (diazepam rectal gel).
Benzodiazepines are absorbed rapidly and almost
completely from the GI tract but are distributed at different rates. Protein
binding of benzodiazepines ranges from 85% to 90%.
Benzodiazepines are metabolized in the liver to
multiple metabo-lites and are then excreted in urine. They readily cross the
placen-ta and are secreted in breast milk.
Benzodiazepines act as:
·
anticonvulsants
·
antianxiety agents
·
sedative-hypnotics
·
muscle relaxants.
Their mechanism of action is poorly understood.
Each of the benzodiazepines can be used in slightly
different ways.
Clonazepam is used to treat the following types of
seizures:
·
absence (petit mal)
·
atypical absence (Lennox-Gastaut syndrome)
·
atonic
·
myoclonic.
Diazepam isn’t recommended for long-term treatment
because of its potential for addiction and the high serum concentra-tions
required to control seizures.
I.V. lorazepam is currently considered the
benzodi-azepine of choice for treating status epilepticus.
I.V. diazepam is used to control status
epilepticus. Be-cause diazepam provides only short-term effects of less than 1
hour, the patient must also be given a long-acting anticonvulsant, such as
phenytoin or phenobarbital, dur-ing diazepam therapy. Diazepam rectal gel is
approved for treatment of
repetitive seizures and has reduced the incidence of recurrent seizures in
children.
Clorazepate is used with other drugs to treat
partial seizures.
When benzodiazepines are taken with CNS
depressants, sedatives, cimetidine, or hormonal contraceptives, depressant
effects are en-hanced. This can cause motor skill impairment, respiratory
de-pression, excessive sedation, CNS depression, and even death at high doses.
(See Adverse reactions to benzodiazepines.)
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