Barbs

Question 1

Barbiturates are

Answer 1

weak acids

Question 2

Barbiturates come prepared as

Answer 2

alkaline solutions

Question 3

barbiturates with substitutions at carbon #2 and#5 have

Answer 3

sedative, hypnotic, properties

Question 4

phenyl group at carbon#5 =

Answer 4

phenobarbital, increased anticonvulsant effect i.e. phenobarbitals

Question 5

methyl group imparts

Answer 5

convulsant activity, i.e. methohexital

Question 6

Sulfuration of barbiturates =

Answer 6

more fat soluble, lipid soluble,

so: shorter duration, more rapid onset, increase potency

Question 7

sulfar at carbon #2 of barbiturate =

Answer 7

thiobarbibutrate

Question 8

Barbiturates: MOA

Answer 8

MOA: Decreases the rate at which GABA dissociates from its receptors.

Increases duration of GABA activated Cl- channel opening

Overall: enhances GABA activity

• Decreases transmission in the sympathetic ganglia : direct acting HYPOTENSION
• Decreases post synaptic membrane sensitivity to Ach -> some muscle relaxation [[not surgical depth!]]

Depresses RAS -> induces sleep

Question 9

onset of barbiturates

Answer 9

“one arm to brain” so rapid

Question 10

Redistribution of barbiturates:

Answer 10

rapid termination of effect is from redistribution

Question 11

metabolism of oxybarbiturates:

Answer 11

hepatic only CYP450

Question 12

metabolism of thiobarbiturates:

Answer 12

hepatic and some ‘extra hepatic’

Question 13

action of barbiturates is terminated by

Answer 13

side chain OXIDATION at C#5 to carboxylic acid.

HYDROLYSIS
DESULFRATION

Question 14

renal excretion of barbiturates

Answer 14

<1% excreted unchanged

Question 15

enzyme induction / inhibition and barbiturates

Answer 15

does not alter metabolism BUT will increase dose requirements

Question 16

more potent isomer of barbiturates

Answer 16

s (-) levo isomer

Question 17

alkinazation of urine favors

Answer 17

barb excretion

Question 18

e 1/2 t of methohexital and thiopental

Answer 18

methohexital = 3.9 hours 
thiopental = 11.6 hours

Question 19

cerebral protective effects of barbs

Answer 19

cerebrovasoconstriction, reduces CBF, decreases ICP, and CMRO2

Question 20

EEG + barbs

Answer 20

isoelectric, potent enough to accomplish this

Question 21

methohexital excitatory movements:

Answer 21

myoclonus and hiccups

Question 22

Barbs + pain

Answer 22

these are anti-analgesic

Question 23

barbs + IOP

Answer 23

Decrease IOP

Question 24

CV effects of barbs

Answer 24

Decreases SNS outflow leads to decrease SVR, SBP subsequent increase in HR from peripheral activation of SNS

Myocardial depression: minimal

SIGNIFICANT myocardial depression and BP with: large doses or pre-existing hypovolemia

ONLY IV.

PO barbs = minimal CV effects.

Question 25

CNS Is not intact in

Answer 25

tiny babies, elderly.

Question 26

histamine release?

Answer 26

with rapid IV admin of barbs

Question 27

respiratory effects of barbs

Answer 27

dose dependent depression of medullary and pontine ventilatory centers

decreased ventilatory RESPONSE to hypoxia / hypercapnia

Question 28

Barbs + laryngeal/cough reflexes

Answer 28

depression of both is incomplete . If dose is not large enough, we can see a “stage 2” repose to a/w manipulation - increased risk of laryngospasm, bronchospasm etc.

Question 29

most potent enzyme inducer =

Answer 29

phenobarbitals

Question 30

hepatic enzyme induction with barbs may lead to

Answer 30

increased metabolism of oral anti-coagulants, phenytoin, TCAs, corticosteroids, vit k.

Question 31

barbs can lead to accelerated production of

Answer 31

heme

Question 32

patients treated with barbs for sz disorders

Answer 32

metabolize drugs about 2x as fast, especially evident in muscle relaxants.

Question 33

venous thrombosis

Answer 33

effect of barbs

Question 34

tolerance of barbs develops

Answer 34

rapidly, more rapidly than can be described by enzyme induction.

Question 35

allergies with barbs

Answer 35

rare: 1:30,000 but high mortality.

allergy most common in atopic patient, those with multiple allergies, prior TPL exposure.

Question 36

things that cant be mixed with barbs

Answer 36

opioids, catechols, NMBs, midazolam, LR,

pancuronium, vecuronium, atracurium, alfentanil, sufentanil, midazolam, LR***

Question 37

to reconstitute barb

Answer 37

must use sterile H2O or NSS

Question 38

Intra-arterial injection of barb

Answer 38

would cause intense vasoconstriction, pain, crystals may form, possible loss of limb

Question 39

to treat intra-arterial injection of barb

Answer 39

dilute with NSS
phenoxybenzamine - noncompetitive antagonist.

prevent thrombosis, brachial plexus block of stellate ganglion block.

papaverine 40-80 mg to vasodilator.

Question 40

drugs to avoid with porphyrias

Answer 40

thiopental
thiamylal
methohexital
etomidate
keterolac
phenacetin
pentazocine

Question 41

methohexital is used

Answer 41

for ECT because we dont want an isoelectric EEG

Question 42

histamine release can cause

Answer 42

bronchoconstriction

Question 43

phenobarbital is excreted

Answer 43

unchanged in the urine, all others are metabolized by CYP450

Question 44

branched chain on the number 5 carbon atom usually has

Answer 44

greater hypnotic activity than the corresponding drug with a straight chain