Barbiturates are used as hypnotic and sedative agents and for inducing anesthesia and treating epilepsy. They are divided into four groups based on their pharmacologic activity and duration of action. All barbiturates cause generalized depression of neuronal activity in the brain by enhancing GABA-mediated chloride currents. Toxicity depends on dose, route, and individual tolerance, and is likely above 5-10 times the hypnotic dose. Treatment involves airway protection, activated charcoal, alkalization to increase elimination of phenobarbital, repeat-dose charcoal, and hemodialysis for severe intoxication.

1. Barbiturates
used as hypnotic and sedative agents, for the induction of
anesthesia
 for the treatment of epilepsy and status epilepticus.
They often are divided into four major groups according to
their pharmacologic activity and clinical use
They include;
ultra-short acting-Thiopental
short acting -Pentobarbital
intermediate acting- Butabarbital
long acting-Phenobarbital

2. Mechanism of toxicity
 All barbiturates cause generalized depression of neuronal
activity in the brain
 Interaction with a barbiturate receptor leads to enhanced
gammaaminobutyric acid (GABA)–mediated chloride currents
and results in synaptic inhibition
 Hypotension that occurs with large doses is caused by
depression of central sympathetic tone as well as by direct
depression of cardiac contractility

3. Toxic dose
• toxic dose of barbiturates varies widely and depends on the
drug, the route and rate of administration, and individual
patient tolerance
• toxicity is likely when the dose exceeds 5–10 times the
hypnotic dose
• abusers may have striking tolerance to depressant effects
• The potentially fatal oral dose of the shorter-acting agents such
as pentobarbital is 2–3 g, compared with 6–10 g for
phenobarbital

4. Treatment
 Emergency and supportive measures :Protect the airway and
assist ventilation and treat coma, hypothermia and hypotension if
they occur.
 Decontamination :Administer activated charcoal orally if
conditions are appropriate.
 Enhanced elimination
1. Alkalization : increases the urinary elimination of phenobarbital .
may potentially contribute to fluid overload and pulmonary edema.
2. Repeat-dose activated charcoal :shown to decrease the half-life
of phenobarbital and its metabolites,
3. Hemodialysis or hemo-perfusion :necessary for severely
intoxicated patients who are not responding to supportive care