Barbiturates

Question 1

Barbiturates

Answer 1

Derived from barbituric acid

Question 2

Oxybarbiturates

Answer 2

Oxygen at 2nd position

Question 3

Thiobarbiturates

Answer 3

Sulfur at 2nd position

Question 4

Thiopental

Answer 4

Sodium pentothal

Question 5

Thiopental PK

Answer 5

Effects terminated by rapid distribution
Oxidized in liver
Long elimination half-life (shorter in pediatrics & prolonged in pregnancy)
Metabolite: Pentobarbital

Question 6

Thiopental MOA

Answer 6

Potentiate GABA receptors
Cortical & brainstem pathways
Inhibits excitatory pathways mediated by glutamate

Question 7

Thiopental PD

Answer 7

CNS effects - burst suppression, isoelectric EEG, ↓ CMRO2, ↓ CBF, ↓ ICP, reverse steal effect, monitor SSEPs
Cardiac - ↓ MAP/CO, ↓ vascular tone, more pronounced in hypovolemia and patients w/ cardiac disease
Respiratory - central apnea, less bronchodilation, airway reflexes maintained

Question 8

Thiopental Dose

Answer 8

2.5-5mg/kg
Decrease dose in elderly, early pregnancy, obesity, pre-medication, & comorbid states
Increase in pediatrics

Question 9

Thiopental SE

Answer 9

Enzyme induction accelerates other drug metabolism - anticoagulants, phenytoin, tricyclic antidepressants, endogenous substances
Exacerbate intermittent porphyria in susceptible patients
Inadvertent arterial administration - medical emergency
- Pain at injection site, decreased flow d/t vasospasm, and thrombus
Treatment: Papaverine arterial administration, heparinization, arteriodilation by regional technique

Question 10

Methohexital

Answer 10

Induction agent choice for patient undergoing ECT

Disadvantage - myoclonus

Question 11

Methohexital Dose

Answer 11

Induction 1-2mg/kg
Rectal administration in pediatrics 25mg/kg
Infusion 50-150mcg/kg/min (sedation & general anesthesia)

Question 12

Methohexital SE

Answer 12

Prolonged infusion associated w/ seizures in susceptible populations