Oral: Barbs

Question 1

Class: Thiopental and Methohexital

Answer 1

Barbiturate/induction agent

Question 2

MOA: Thiopental

Answer 2

mimics GABA and increases the association of GABA to the GABA-A receptor = hyperpolarization of the cell and ⬇neuronal transmission;
⬇transmission in sympathetic ganglion = hypotension;
⬇ postsynaptic membrane sensitivity to ACh= muscle relaxation depresses RAS= sleep;
NO analgesic effects.

Question 3

Pharmacokinetics: Thiopental

Answer 3

70% PB, high lipid solubility, crosses BBB and placenta
Onset = fast, redistributes in 2-4 min
E1/2t = 11.6 hrs
metabolized by CYP450 with some extrahepatic metabolism & renal clearance

Question 4

Side Effects: Thiopental

Answer 4

⬇CBF, ICP, CMRO2, IOP, can cause isoelectric EEG;
Histamine release,⬇BP, cardiac depression;
respiratory depression, ⬇laryngeal cough reflexes; ⬆heme production;
induces CYP450;
anaphylaxis with high mortality

Question 5

Contraindications: Thiopental

Answer 5

porphyria, asthma, pregnancy, monitor drugs metabolized by CYP450

Question 6

Dose: Thiopental

Answer 6

3-5 mg/kg IV

Question 7

MOA: Methohexital

Answer 7

mimics GABA and increases the association of GABA to the GABA-A receptor = hyperpolarization of the cell and ⬇neuronal transmission;
⬇transmission in sympathetic ganglion = hypotension;
⬇ postsynaptic membrane sensitivity to ACh= muscle relaxation depresses RAS= sleep;
NO analgesic effects.

Question 8

Pharmacokinetics: Methohexital

Answer 8

70% PB, high lipid solubility, crosses BBB & placenta
Onset = very fast, redistributes in 10 min
E1/2t = 4 hours
metabolism only in liver by CYP450, excreted in urine

Question 9

Side Effects: Methohexital

Answer 9

⬇CBF, ICP, CMRO2, can cause sz; 
Histamine release= ⬇BP, ⬆HR; 
resp depression, apnea, hiccup, cough; 
myoclonus; 
pain on injection; 
⬆heme production; 
induces CYP450

Question 10

Contraindications: Methohexital

Answer 10

porphyria, asthma, pregnancy, monitor drugs metabolized by CYP450

Question 11

Dose: Methohexital

Answer 11

1-2 mg/kg IV

Question 12

Class: PHENYTOIN and PHENOBARBITAL

Answer 12

Barbiturate/anticonvulsant

Question 13

MOA: PHENYTOIN

Answer 13

dec neuronal excitatability – inhibits Na + Ca ion transport across neuronal cell mem.

Tx: ventric arrhythmias untx by lido + dig OD ?

Question 14

PK: PHENYTOIN

Answer 14

90% PB
ONSET: 30min
DOA: dose dependent
CYP450 system (98%) 
1st order < 10mcg/ml
0 order > 10 mcg/ml
Elim: renal
E ½ T: dose dependent

Question 15

SE: PHENYTOIN

Answer 15

1. dec BP, HR, arrhythmias
2. CYP450 inducer
3. venous irritant
4. thrombophlebitis

Question 16

CI: PHENYTOIN

Answer 16

Pregnancy, porphyria, asthma

Question 17

Dose: PHENYTOIN

Answer 17

10 – 15 mg/kg
Infusion no faster than 50 mg/min in adults to prevent dec bp/dysrhythmias
GIVE SLOWLY

Question 18

MOA: PHENOBARBITAL

Answer 18

Activate GABAa rec of post-syn cell
inc Cl- conductance = hyper-polarizes = inh neuronal transmission
Causes: sedation, dec motor activity.
At high dose = anticonvulsant

Question 19

PK: PHENOBARBITAL

Answer 19

30% PB
ONSET: 5min
DOA: 4 – 10 hrs, Peak = 30 min
CYP450 system 
Elim: 50% unchanged in urine
E ½ T: 50 – 140 hrs

Question 20

SE: PHENOBARBITAL

Answer 20

1. bone marrow suppression
2. agranulocytosis
3. liver toxicity
4. stevens johnsons

Question 21

CI: PHENOBARBITAL

Answer 21

Hypersensitivity, porphyria, liver dysfx, resp disease

Question 22

Dose: PHENOBARBITAL

Answer 22

Status ep: loading = 10 – 20 mg/kg
I: 5 – 10 mg/kg q15 – 30 m
M: 1 – 5 mg/kg/day divided
Max = 30 mg/kg