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Pharmacology > Barbiturates > Flashcards

Barbiturates Flashcards

1
Q

Barbiturate derived from

A

Barbituric acid

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2
Q

Are all barbiturates racemic mixtures?

A

Yes

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3
Q

Sulfuration substitution means

A

Greater lipid solubility

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4
Q

Phenylephrine group replacement results in

A

Anticonvulsant properties

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5
Q

Methyl group replacement results in

A

Convulsive activity

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6
Q

For barbituric acid to have CNS effects what must occur?

A

Substitution at #2 and 5 carbon

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7
Q

3 uses for barbiturates

A

1- induction of anesthesia
2- tx of elevated ICP
3- ECT, retrobulbar block, cardioversion

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8
Q

Clinical use of barbiturates declining because of (4)

A

1- lack of specificity and CNS effect
2- lower therapeutic index
3- greater tolerance and liability for abuse
4- high risk of drug interactions

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9
Q

Major drawback of barbiturates for anesthetic

A

Hang-overs

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10
Q

Methohexital and seizure threshold

A

Decreases seizure threshold

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11
Q

R/t increased risk of dose related excitatory phenomena like myoclonus and hiccups

A

Methohexital

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12
Q

Recovery rate of methohexital

A

Awake in 3-7 minutes

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13
Q

Induction dose of methohexital

A

1-2mg/kg

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14
Q

Methohexital dose to induce anesthesia in peds and uncooperative

A

20-30mg/kg rectally

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15
Q

ECT dose of methohexital

A

1 mg/kg

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16
Q

Half life of thiopental.

Anesthesia application

A

11.5-26 hours

Slow emergence

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17
Q

Sodium thiopental r/t hemodynamics

A

Large doses cause hemodynamic instability

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18
Q

Thiopental is dosed by

A

Ideal Body Weight

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19
Q

Thiopental induction dose

A

3-5mg/kg

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20
Q

Barbiturates quick awakening is due to

A

Redistribution

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21
Q

Slow wake up of thiopental is due to

A

Redistribution from peripheral tissues to central resulting in hang-over effect

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22
Q

Barbiturate complete elimination from body is dependent on what?

A

Metabolism

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23
Q

Effect site equilibration time of thiopental and methohexital is

A

Rapid

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24
Q

Barbiturate lipid solubility is determined by

A

Solubility of non-ionized molecules

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25
Q

Barbiturates and plasma protein binding

-which binds more

A

High plasma protein bound

Thiopental greatest (72-86%)

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26
Q

Most lipid soluble and possess greater anesthetic potency (barbs)

A

Non-ionized barbiturates

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27
Q

3 that determine barbiturate pharmacokinetic

A
  • lipid solubility
  • protein binding
  • ionization
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28
Q

Shock = decreased skeletal muscle perfusion. What change to barb dose?

A

Decrease dose

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29
Q

Principal mechanism for barbiturate early awakening

A

Redistribution from central to peripheral compartments

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30
Q

Main initial site for distribution of barbs

A

Skeletal muscle

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31
Q

Only compartment where thiopental concentrations continue to increase 30 minutes post injection

A

Fat = hang-over

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32
Q

Effect of acidosis on barbs effect

A

Increases effect

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33
Q

Alkalosis effect on barbiturate effects

A

Decrease effects

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34
Q

Non-ionized barbiturates result in

A
  • greater CNS access

- greater lipid solubility

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35
Q

Metabolism of oxibarbiturates

A

Hepatic metabolism only

36
Q

Metabolism of thiobarbiturates

A

Mainly hepatic but also kidney and CNS

37
Q

Metabolites of barbs

A

Inactive

38
Q

Capacity of liver to metabolize barbiturates

A

Large capacity

39
Q

Thiopental metabolism

A

Slow

10-24% metabolized every hour

40
Q

Most rapid metabolism of barbiturates?

Why?

A

Methohexital

  • lower lipid solubility so less plasma protein bound, more available for metabolism
41
Q

determines complete recovery from barbs

A

Metabolism

42
Q

Peds pt have _______ recovery from barbs due to ________

A

Faster recovery r/t more rapid hepatic clearance

43
Q

Elimination 1/2 time of thiopental greater in _________ r/t

A

Greater in obese patients due to greater VD form more fat storage

44
Q

All barbs are filtered by renal glomeruli but ________ limits filtration

A

High protein binding

45
Q

____________ favors reabsoption of drugs back into blood

A

High barbiturate lipid solubility

46
Q

__________ of barbs eliminated in us-metabolized form

A

Less than 1%

47
Q

Enzyme induction stimulation from barbiturates persists for

A

Up to 30 days after last dose

48
Q

Enzyme induction of barbs results in greater metabolism of

A 
Coumadin
Dilantin
TCA
Corticosteroid
Vit K
49
Q

Barbs interact with _______ in CNS- causing

A

GABA- increased duration of GABA activated chloride channels

50
Q

________ very sensitive to barb effects compared to other tissues

A

CNS

51
Q

Barbs and SNS

A

Depresses SNS= lower BP

High dose = circulatory collapse

52
Q

Tolerance to sedative effect of barbs occurs at greater rates than anti convulsants and lethal effects so

A

Barbiturate therapeutic index decreases as tolerance increases

53
Q

Pt on highly protein bound meds (ASA, Dilantin) and thiopental effects

A

Increased thiopental effects

54
Q

Barbs effect on CNS

A

CNS depressant

Range from mild sedation to total anesthesia

55
Q

Barbs effect on cerebral blood volume by

A

Decrease CBV by cerebral vascular vasoconstriction

56
Q

Barbs good or bad for elevated ICP

A

Good for high ICP

57
Q

Barbs and cerebral flow

A

Intense cerebral vasoconstriction

58
Q

Barbs and EEG

A

Isoelectric EEG max depression of CMRO2 by 55%

59
Q

High dose barb to lower ICP results in

A

Hypotension and worsen cerebral perfusion pressure

60
Q

Thiopental causing isoelectric EEG results in

A

Peripheral vasodilation and myocardial depression

61
Q

Focal ischemia protection from barbs useful in what cases

A

CEA
Thoracic aneurysm
Profound hypotension

62
Q

Small barb dose _______ pain threshold

A

Lowers

63
Q

Thiopental and EP

A

Do not interfere with EP monitoring

64
Q

At what dose thiopental is there no visible myocardial depression in healthy pt

A

5mg/kg

65
Q

Barbs have ______ inotropic effects at high doses

A

Negative

66
Q

Barbs and BP

A

Lower BP

67
Q

Hypovolemic pt and barbs

A

Should not get barbs

68
Q

Give barbs______

Why?

A

Quick

Slower admin results in higher total dose

69
Q

Laryngeal and cough reflexes with barbs

A

Do not depress laryngeal and cough reflexes

70
Q

Barbs and medullary and pontine ventilatory centers

A

Depression

71
Q

Greatest barb for hepatic enzyme inductions

A

Phenobarbital

72
Q

Cirrhosis and barbs

A

Exaggerated response, bc more free drug to elicit effects

73
Q

Less than _____% of barbs eliminated unchanged

A

1%

74
Q

Barbs and GI tract

A

Well absorbed from GI tract

75
Q

Main site of redistribution of barbs from central compartment

A

Skeletal muscle

76
Q

Barbs and skeletal muscle relaxation

A

Does not occur

77
Q

Allergic rx with barbs

Seen in

A

Very rare

Prior thiopental exposure
IgE mediated hypersensitive disorder

78
Q

Thiopental allergic reaction mortality

A

High

79
Q

Diseases of accelerated heme production resulting in jaundice

A

Porphyria

80
Q

Barbs effect on porphyria

A

Symptoms exaggerated

81
Q

Barbs and porphyria patients

A

CONTRAINDICATED

82
Q

Neonates and barbs

A

Greater sensitivity bc less protein binding sites

83
Q

If give thiopental in artery

A

Gangrene and nerve damage

84
Q

Venous thrombosis after barb administration for induction is due to________ not__________

A

Deposition of barbiturate crystals NOT alkaline pH (10)

85
Q

Best advantage of thiopental over propofol

A

Thiopental mixtures are strongly bactericidal

Pharmacology (6 decks)

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