Barbiturates

Barbiturates are rarely used outside of treatment of refractory seizures (phenobarbital) and for general anesthesia (thiopental). Benzodiazepines and other medications used to treat anxiety and sleep disorders have a much higher safety profile.  

Class Drugs

• Thiopental

• Pentobarbital

• Secobarbital

• Amobarbital

• Phenobarbital

Class Mechanism of Action

• Potentiation of GABA action

Binds to location separate from benzodiazepines on GABA receptor.

• Prolongs duration of chloride channel opening allowing increased chloride entry into cell.

• Results in CNS depression in dose dependent fashion.

Effects range from sedation, hypnosis, anesthesia, coma, and death.

• Blocks glutamate (excitatory) receptors.

• Diminished response to CO2 at chemoreceptor.

Leads to respiratory depression and respiratory arrest.

Class Application

Anesthesia

• Use is limited due to the advent of other more effective agents.

Anticonvulsant

• Mediated by alpha-1-GABA-A receptors.

• Susceptible to tolerance

• Decreases sleep latency.

• Increase of stage II non-rem sleep

• Decrease in REM sleep

Class Adverse Effects

• Drowsiness, mental and physical sluggishness

• Drug "hangover" impairs function hours after waking.

• Induces cytochrome P450 system.

Reduces the effectiveness of other drugs metabolized by this system.

• Contraindicated in acute intermittent porphyria

• Withdrawal

Can be deadly.

• Tremor, anxiety, nausea, delirium

• Seizures

• Cardiac arrest

Drug Table

Drug Name	Application	Comments	Image
Thiopental	Anesthesia Induction	Rarely used; Very short-acting (~20 min)	"Theo" and "Pen"
Pentobarbital	Pre-anesthetic; Insomnia	Short-acting	"Pen", "Toe", and "Barb"
Secobarbital	Epilepsy		"Second Base" and "Barb"
Amobarbital	Insomnia; Refractory Seizures		"Ammo" and "Barb"
Phenobarbital	Refractory Seizures	Impaired cognitive development in children; Impaired cognitive function in adults; Can precipitate acute intermittent porphyria by increasing porphyrin synthesis (induction of hepatic delta-aminolevulinic acid synthase)	"Fence" and "Barb"