MARIA FE SALVADOR NAVARRETE MD
Barbiturates and Similarly Acting
used as sedative-hypnotic agents in 20th century
high abuse and addiction potential,
a narrow therapeutic range with low therapeutic index,
and unfavorable side effects.
The use of barbiturates and similar compounds such as
meprobamate (Miltown) has been practically eliminated by
buspirone (BuSpar), and hypnotics such as zolpidem
(Ambien) and zaleplon (Sonata), which have a lower abuse
potential and a higher therapeutic index than the
the barbiturates and similarly acting drugs still have a role
in the treatment of certain mental disorders.
well absorbed after oral administration.
The binding of barbiturates to plasma proteins is high, but
lipid solubility varies.
metabolized by the liver and excreted by the kidneys.
The half-lives of specific barbiturates range from 1 to 120
hours (Table 36.8-1).
Barbiturates may also induce hepatic enzymes (cytochrome
P450), thereby reducing the levels of both the barbiturate
and any other concurrently administered drugs
metabolized by the liver.
The mechanism of action of barbiturates involves the Î³-
aminobutyric acid (GABA) receptorâ€“benzodiazepine
receptorâ€“chloride ion channel complex.
Methohexital (Brevital) is commonly used as an
anesthetic agent for electroconvulsive therapy
It has lower cardiac risks
Used intravenously, methohexital produces rapid
unconsciousness and, because of rapid
redistribution, it has a brief duration of action (5
to 7 minutes)
Typical dosing for ECT is 0.7 to 1.2 mg/kg.
Methohexital can also be used to abort
prolonged seizures in ECT or to limit postictal
Phenobarbital (Solfoton, Luminal), the most
commonly used barbiturate for treatment of
seizures, has indications for the treatment of
generalized tonic-clonic and simple partial
Parenteral barbiturates are used in the
emergency management of seizures
independent of cause. Intravenous (IV)
phenobarbital should be administered slowly,
10 to 20 mg/kg for status epilepticus.
Amobarbital (Amytal) has been used
historically as a diagnostic aid in a number of
including conversion reactions,
and unexplained muteness,
and to differentiate stupor of depression,
schizophrenia, and structural brain lesions.
The barbiturates reduce sleep latency and the
number of awakenings during sleep, although
tolerance to these effects generally develops
within 2 weeks.
Discontinuation of barbiturates often leads
to rebound increases on
electroencephalogram (EEG) measures of
sleep and a worsening of the insomnia.