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Flashcards in Methohexital Deck (23):
1

What is the trade name of Methohexital?

Brevital

2

What is the formal drug class of Methohexital?

Barbiturate/ Oxybarbiturate

3

What are the clinical uses of Methohexital?

-IV/IM/Rectal induction and IV maintenance of anesthesia in short procedures with minimal painful stimuli
-treatment of Increased ICP

4

What is the MOA of Methohexital?

-produces sedative-hypnotic effects via interaction with GABA in the CNS and by depressing the RAS
-GABAa increases transmembrane chloride, resulting in hyperpolarization of the post-synaptic cell membrane and thus inhibition of the post-synaptic neurons
-also targets glutamate, adenosine and neuronal nicotinic receptors
-selectively depresses transmission in SNS ganglia resulting in decreased BP during IV administration

5

How is Methohexital metabolized?

-Occurs in the liver through N-dealkylation and oxidation to inactive metabolites
-side chain oxidation to form the inactive metabolite, 4-hydromethohexital is the most important biotransformation involved in termination of biologic activity

6

What is the elimination 1/2 life?

4 hours

7

How is Methohexital cleared?

-much higher hepatic extraction ratio (compared with TPL) therefore hepatic blood flow and cardiac output more likely to influence metabolism

8

What is the redistribution of Methohexital?

-IV administration results in rapid uptake by the brain (within 30 secs) and rapid induction of sleep
-early awakening is a result of redistribution away from CNS

9

What is the DOA of Methohexital?

5-10 minutes as a result of its lipid solubility and rapid redistribution into muscle and organs with high blood flow

10

How is Methohexital eliminated?

clearance 9.3-12.1 mL/kg/min
Excreted via the kidneys

11

What is the volume of distribution of Methohexital?

Vd is 1.9-2.2 L/kg

12

Is Methohexital protein bound?

approximately 73%

13

What are the CNS side effects of Methohexital?

-Hiccups, coughing, and/or muscle twitching
-produces a dose-dependent decrease in CMRO2 by up to 50% of normal
-Reduction in O2 requirements may offer protection during transient focal ischemic events
-seizures may be elicited in those with previous history of convulsive activity, especially partial seizure disorder
-cerebral vasoconstriction with reduction in cerebral blood flow and ICP- cerebral perfusion pressure maintained because reduction in ICP exceeds MAP
-pain on injection

14

What are the respiratory side effects of Methohexital?

-Depressed ventilatory response to hypercarbia or hypoxemia as a result of central depression
-dose dependent decrease in RR and TV- apnea may result for 30-90 seconds after a sleep dose

15

What are the CV effects of Methohexital?

-following induction, temporary dose-dependent decrease in ABP and CO, and reflex tachycardia

16

What are the contraindications to the use of Methohexital?

-Contraindicated in patients who cannot tolerate GA
-Porphyria
-known sensitivity

17

When should Methohexital be used with caution?

in patients with:
asthma
obstructive pulm. disease
severe HTN or hypotension
Hypovolemia
Myocardial disease
CHF
Severe anemia
Extreme obesity

18

Metabolism of Methohexital is influenced by what other drugs?

Phenytoin
Halothane
Anticoagulants
Corticosteroids
Ethyl Alcohol
Opioids
Propylene Glycol

19

What should NOT be mixed with Methohexital?

Succinylcholine and other
Acidotic medications because precipitation will occur

20

What is the induction dose of Methohexital?

1 - 2 mg/kg IV of 1% solution

21

What is the maintenance IV dosage of Methohexital?

Intermittent injections of 20-40mg of 0.2% or 1% solution every 4-7 minutes, or as required

22

What is the rectal dose of Methohexital and when is it usually used?

20 - 30 mg/kg for induction of anesthesia in uncooperative or pediatric patients

23

What is an important airway consideration of Methohexital?

-it does not completely obtund a/w reflexes; asthmatics may develop bronchospasm and lightly anesthetized patient may develop laryngospasm