Barbiturates

Question 0

CNS Effects of Barbituates

Answer 0

• reduce anxiety (sedative)
• shorten time to sleep (hypnotic)
• occur together

Question 1

Mechanism of action of Barbituates

Answer 1

• Allosteric agonists at GABA-A receptor
• Bind to barbiturate binding site on GABA-A receptor
• Potentiate action of GABA
• High doses = direct GABA-A receptor agonists
• Inhibit AMPA, voltage dependent Na+ and K+ channels & nicotinic receptors

Question 2

Pharmacokinetics of Barbituates

Answer 2

Strongly induce cytochrome P450 enzyme (causes multiple drug interactions)

Question 3

Barbiturate intoxication:

Answer 3

• Therapeutic index is narrow (10x therapeutic dose)

- OD can be fatal (Tx is supportive)

Question 4

Barbituates

Answer 4

• Phenobarbital
• Secobarbital
• Thiopental

Question 5

Physical dependable of Barbituates:

Answer 5

8-12 hours after last dose:
-minor sx; tremors, restlessness, anxiousness, wkness, N/V, insomnia
2 Days after last dose:
-increase SNS, delirium, seizures, death

Question 6

Tx of Drug withdrawal for Barbituates:

Answer 6

Switch to long acting Barbituate

Then gradually reduce dose