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Anes 516: Pharmacology > Lecture 2: Benzodiazepines > Flashcards

Lecture 2: Benzodiazepines Flashcards

1
Q

In Daltons, how much exchange of molecules between mother and fetus takes place?

A

<1000 Daltons

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2
Q

What are four factors that affect transfer of molecules between mother and fetus?

A

1) Maternal protein binding
2) Molecular weight
3) Lipid solubility
4) Degree of ionization

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3
Q

Fear of suffering and death, loss of control, and frustration caused by the inability to communicate

A

Anxiety

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4
Q

Onset, peak, and duration of Midazolam

A

Onset: 30-60 seconds
Peak: 3-5 minutes
Duration: 15-80 minutes

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5
Q

Onset, peak and duration of Lorazepam

A

Onset: 1-2 minutes
Peak: 20-30 minutes
Duration: 6-10 hours

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6
Q

Which benzo is administered preoperatively PO?

A

Diazepam

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7
Q

Which benzo has a duration of 6-10 hours?

A

Lorazepam

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8
Q

Which benzo has a duration of 15-80 minutes?

A

Midazolam

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9
Q

Which benzo peaks at 20-30 minutes?

A

Lorazepam

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10
Q

Which benzo starts working 30-60 seconds after administration?

A

Midazolam

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11
Q

What is the half-life of midazolam?

A

1.9 hours

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12
Q

What is the half-life of diazepam?

A

43 hours

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13
Q

What is the half-life of lorazepam?

A

14 hours

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14
Q

Why do benzos have different half-lives?

A

D/t difference in rate of metabolism in the liver

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15
Q

Why do benzos often have a longer duration in the elderly?

A

Decrease in liver blood flow

Decrease in skeletal muscle = decrease in volume of distribution

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16
Q

You have a very drunk, belligerent patient enter your OR, and you administer midazolam. What effect do you expect to see?

A

The midazolam will have a synergistic effect with the alcohol and cause exaggerated response to the drug, but the drug will be eliminated faster because the alcohol has put the liver’s metabolic processes in overdrive to get rid of the levels of poison in the body.

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17
Q

Describe the chemical structure of a benzodiazepine.

A

A benzodiazepine has a 7-member diazepine ring at its core with at least one benzene ring attached to it.

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18
Q

What chemical structural difference does midazolam exhibit vs. other benzos? What is the physiological effect?

A

Its diazepine ring can open up or close, switching from lipid-soluble (closed) to water-soluble (open). The ring may open in high temperatures of plasma.

Because midazolam can open its ring, it can be water soluble which means as long as it is stored in an acidic solution, it will remain liquid in solution. However, once it is injected into blood plasma, it immediately changes its molecular structure and closes its diazepine ring, allowing it to be lipid-soluble and have an effect in plasma.

The other two benzos require a solvent to stay water soluble–solvent burns upon administration.

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19
Q

What is the major inhibitory neurotransmitter of the CNS?

A

GABA

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20
Q

What is the mechanism of GABA?

By what means is it inhibitory?

A

Binds to GABA receptors and causes a conformational change to allow Cl- to flow into cell
Cl- hyper-polarizes the cell and prevents further neurotransmission + putting brain to sleep

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21
Q

If GABA is the major inhibitory neurotransmitter of the CNS, what is its opposite?

A

Glutamate, the major excitatory neurotransmitter of the CNS

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22
Q

In what way do benzos affect GABA activity?

A

Benzos bind to GABA receptors and increase their affinity for GABA, hyperpolarizing the cell and calming neurotransmission

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23
Q

GABA-a receptors are located on what neurons?

A

Post-synaptic neurons

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24
Q

The mechanism of action of GABA-a receptors begins where? And then?

A

Cerebral cortex > hypothalamus > midbrain > hippocampus > medulla > spinal cord

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25
Q

If 20% of GABA receptors are occupied by benzos, what physiological effect?

A

anxiolysis

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26
Q

If 30-50% of GABA receptors are occupied by benzos, what physiological effect?

A

sedation

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27
Q

If 60% of GABA receptors are occupied by benzos, what physiological effect?

A

unconscious

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28
Q

By what mechanism are benzodiazepines anticonvulsants?

A

Seizures are caused by excitatory stimulation of the CNS, but benzos cause inhibitory stimulation to overcome excitatory stimulation to prevent seizures

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29
Q

What are the effects of benzos?

A

1) Sedation, hypnosis
2) Anxiolysis
3) Anticonvulsant
4) Anterograde amnesia

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30
Q

What are some things that benzos do NOT do for us in the OR?

A

1) Analgesia
2) Antidepressant
3) Antipsychotic
4) Protection against stress of intubation

31
Q

If you intubate a patient that is unconscious due to benzos, what sort of physiological response should you expect to see?

A

Patient will have sympathetic response d/t no analgesia provided by benzos

32
Q

What are the two effects of benzos that benefit us most in our practice?

A

1) Relief of anxiety

2) Sedation and amnesia before and during medical procedures

33
Q

If you wish to administer midazolam to your pediatric patient, how do you go about that? Dose? Method of administration? At what time? Max dose?

A

Give them 0.5 mg/kg PO 30 minutes before procedure

Max dose = 15 mg

34
Q

What is an appropriate IV dose of midazolam in adults?

A

1-5 mg

35
Q

IV sedation dose of midazolam in ICU?

A

Administer 0.5 - 4 mg IV as a loading dose, then give a drip, 1-7 mg/hr IV

36
Q

IV induction dose of anesthesia for midazolam?

A

0.1 - 0.2 mg/kg IV

37
Q

Which benzo suppresses seizure activity? What dose?

A

Diazepam

0.1 mg/kg IV

38
Q

Does a time limit exist for benzo drips?

A

Yes, after 72 hours benzos can cause hyperlipidemia and tachyphylaxis, so you shouldn’t administer a benzo drip for longer than 3 days.

39
Q

What is cross tolerance?

A

The concept of one drug alleviating symptoms of withdrawal from another drug; it also means that tolerance of one drug will result in tolerance of another drug

40
Q

If you take midaz PO, how much of the drug is lost to first-pass metabolism in the liver?

A

50%

41
Q

What kind of effect do benzos have in obese and elderly patients?

A

Benzos are highly lipophilic, meaning they have a high volume of distribution in patients that are obese (also, elderly–elderly patients lose muscle mass for fat). Drugs that have a high volume of distribution are less likely to be bound to protein, so theoretically benzos would be more active in these patients and reduced doses are required.
20% less
Use IBW for obese patients.

42
Q

How do you calculate IBW in males?

A

50 kg + 2.3 kg for each inch over 5 feet

43
Q

How do you calculate IBW in females?

A

45.5 kg + 2.3 kg for each inch over 5 feet

44
Q

Where are benzos metabolized? By what mechanism?

A

In the liver; oxidized by cyt P450

45
Q

Why do benzos stick around longer in elderly patients?

A

Less hepatic blood flow means less metabolism

46
Q

Metabolites of benzos produced in the liver via oxidation are excreted via the ___________.

A

Kidneys

47
Q

What effect does ESRD have on patients if you give them benzos?

A

There is no difference in effect because although there is likely reduced clearance of metabolites, the metabolites that the liver produces are inactive, so just because metabolite levels increase doesn’t mean there is any sort of effect.

48
Q

Effect of benzos on CMRO2 and CBF

A

Decreases them, so decreases metabolic oxygen requirements (makes sense because they inhibit neural activity)

49
Q

Effect of benzos on ICP

A

No change

50
Q

Are benzos neuroprotective?

A

No evidence to indicate they are

51
Q

How do benzos affect ventilation?

A

Dose dependent decrease in ventilation

52
Q

Cardiovascular effects of benzos?

A

Minor decrease in blood pressure and compensatory increase in heart rate

53
Q

Do benzos cross the placenta?

A

Yes, just like alcohol does, and that’s why we cannot administer them to pregnant women.

54
Q

What is the difference between the mechanism of action as an anticonvulsant between benzos and barbiturates?

A

Benzos are anti-convulsants because they encourage GABA activity, opening Cl- channels to hyperpolarize and therefore indirectly suppress the CNS
Barbiturates are anti-convulsants because they directly suppress the CNS

55
Q

Diazepam 0.1 mg/kg IV can effectively treat which convulsions related to convulsions?

A

1) Lidocaine toxicity
2) Delirium tremens (alcohol withdrawal-induced convulsion)
3) Status epilepticus

56
Q

Which is more potent, midazolam or diazepam?

A

Midazolam is 2-3x more potent than diazepam?

57
Q

What is the common name of diazepam?

A

Valium

58
Q

What is the pK of midazolam?

A

pK = 6.15

59
Q

What is the specific antagonist of midazolam?

A

Flumazenil

60
Q

Which benzodiazepine is associated with severe birth defects?

A

Librium (chlorodiazepoxide)

61
Q

What is the metabolite of midazolam? What is its level of activity?

A

1-hydroxymidazolam

50% level of activity of midazolam

62
Q

What drugs may slow metabolism of midazolam?

A

Any drug that inhibits cyt p450:

Cimetidine (H+ channel blocker), erythromyocin, Ca++ channel blockers

63
Q

Dosing lorazepam at 0.05 mg would be equivalent to dosing midazolam or diazepam at?

A

Midazolam: 0.15 - 0.5 mg
Diazepam: 0.3 - 0.5 mg

64
Q

What is the common name of Lorazepam?

A

Ativan

65
Q

Why do lorazepam and diazepam cause thrombophlebitis and venous irritation?

A

They are not water-soluble like midazolam is, so they must be stored in a solvent to be administered intravenously; that solvent is propylene glycol, which burns when it comes into contact with blood.

66
Q

Name two benzos that treat insomnia:

A

1) Flurazepam

2) Oxazepam

67
Q

Generic name of xanax?

A

Alprazolam

68
Q

Generic name of ambien?

A

Zolpidem

69
Q

What is flunitrazepam?

A

Rohypnol…date rape drug that causes anterograde amnesia

70
Q

Why is flumazenil most effective in reversing midazolam as compared to other benzos?

A

They have similar half-lives. If you wish to reverse diazepam and lorazepam, you must continue to redose flumazenil: otherwise, your patient may experience a phenomenon known as resedation

71
Q

What is the dose of flumazenil?

A

0.1 to 0.2 mg IV, with maximum at 3 mg

72
Q

What are some adverse reactions of flumazenil?

A 
CNS manifestations
Resedation
Cardiovascular effects
Seizures
Alterations in ICP and CPP
73
Q

What effect does flumazenil have in regards to benzo withdrawal?

A

It seems to dampen benzo withdrawal effects.

Anes 516: Pharmacology (5 decks)

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