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Pharmacology 680 > Antiemetics > Flashcards

Antiemetics Flashcards

1
Q

Are male or female more at risk for PONV?

A

female, especially with PDNV

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2
Q

Results of PONV

A

delayed discharge
increased cost and convenience
electrolyte imbalance
increased bleeding

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3
Q

Risk Factors for PONV in Adults

–Positive overall

A 
Female sex (B1)
History of PONV or motion sickness 
Nonsmoking (B1)
Younger age (B1)
General versus regional anesthesia
Use of volatile anesthetics and nitrous 
Postoperative opioids
Duration of anesthesia (B1)
Type of surgery
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4
Q

what types of surgeries are at greater risk for PONV?

A

choley, laparoscopic, gynecologic

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5
Q

What 4 things are taken into account with the apfel risk score for PONV?

A

female gender
non-smoker
history of PONV
postoperative opioids

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6
Q

5 risk factors for PDNV in adults?

A 
female sex
hx PONV
Age <50
use of opioids in pacu
nausea in pacu
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7
Q

Risk factors peds?

A

increased incidence age 3 thru puberty, NOT gender specific

vomiting incidence is 2X adults at 40%

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8
Q

6 things to minimize PONV risk factors

A
  • avoid GA
  • use propofol
  • avoid nitrous
  • avoid volatiles
  • minimize opioids
  • hydrate
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9
Q

Pathophysiology of PONV

A

Brainstem vomiting center located in
the lateral medullary reticular
formation

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10
Q

7 receptors involved with patho of PONV?

A 
Acetylcholine - Muscarinic
Histamine H1
Serotonin 5-HT3
Dopamine
Substance P
GABA
Neurokinin-1
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11
Q

Afferent Input to the Vomiting Center - Chemoreceptor trigger zone (4th ventricle) receptors activated

A

dopamine, serotonin 5-HT, opioid receptors

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12
Q

Afferent Input to the Vomiting Center -Vestibular system (motion sickness) receptors activated

A

muscarinic and H1 receptors

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13
Q

Irritation of the pharynx (vagus nerve) causes

A

gag and retch response

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14
Q

Vagal and enteric afferents (mucosa of the GI

tract)

A

5-HT33 receptors activated by serotonin released by the receptors activated by serotonin released by the
mucosa, then stimulate vagal input to CTZ and vomiting center

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15
Q

CNS afferent input to vomiting center?

A

stress and anticipatory vomiting

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16
Q

the vomiting center sends efferent signals via which cranial nerves

A

V, VII, IX, X, XII through pns fibers and alpha motor neurons

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17
Q

where does the efferent output from the emetic center travel through?

A

phrenic and spinal nerves of abd wall musculature

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18
Q

CTZ stand for?

A

chemoreceptive trigger zone

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19
Q 
decreasing dopamine input at the chemoreceptor 
trigger zone as well as anxiolysis; it 
may also decrease adenosine reuptake
leading to decreased synthesis, release,
and postsynaptic action of dopamine at  
the CTZ
A

benzodiazepines

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20
Q

when should you give a benzo if using solely as antiemetic?

A

end of the case

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21
Q

MOA: Anticholinergic effect, histamine receptor

blockade

A

antihistamines

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22
Q

3 antihistamines you can give as antiemetic

A

diphenhydramine, meclizine, dimenhydrinate

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23
Q

What type of PONV do antihistamines work best for?

A

motion sickness, weak effect with other causes

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24
Q

limitations of antihistamines for PONV?

A

sedation, dizziness, confusion, dry mouth, urinary retention

25
Q

MOA: Inhibition of dopamine and muscarinic

receptors

A

phenothiazines

26
Q

2 examples of phenothiazines?

A

Prochlorperazine (Compazine 2.5-10mg IV),

promethazine (Phenergan 25mg IV)

27
Q

Limitations phenothiazines

A 
sedation
extrapyramidal effects
lowers seizure threshold
hypotension (alpha blockade)
pseudoparkinson's
28
Q

MOA: Antimuscarinic (vestibular system), antagonizes histamine and serotonin

Blocks transmission to the medulla of impulses from overstimulation of vestibular apparatus

A

scopolamine

29
Q

how should you apply scopolamine patch?

A

Apply patch 60 minutes prior to induction and it can provide adequate drug levels for 48-72 hours. (5 mcg/hr for 72 hours – total dose absorbed less than 0.5 mg)

30
Q

Limitations scopolamine?

A

ocular effects (glaucoma), restlessness, delirium, sedation, dry mouth, tachycardia

31
Q

MOA: Dopamine blockade (alpha blockade)

Extremely sedating, dissociative state

A

Butyrophenones (droperidol, Inapsine)

32
Q

Dose of Butyrophenones (droperidol, Inapsine)

A

Dose: 0.625-1.25 mg IV (0.05 mg/kg)

MAX 2.5 mg

33
Q

Limitations butyrophenones

A

prolonged QT interval (torsade de pointes), extrapyramidal effects (Parkinson’s, elderly avoid), hypotension, sedation

34
Q

how to treat extrapyramidal effects of Butyrophenones (droperidol, Inapsine)

A

benadryl

35
Q

MOA: Dopamine blockade in the CTZ and cholinergic stimulus to GI tract (increased gastric and small intestine motility)

A

Metoclopramide (Reglan)

36
Q

increased incidence of extrapyramidal effects (restlessness, dystonias, parkinsonian) with reglan when given with

A

phenothiazines or droperidol

37
Q

Avoid reglan with:

A

: intestinal obstruction, Parkinson’s

38
Q

WHAT IS Serotonin (5-HT)

A

endogenous vasoactive substance and neurotransmitter (emesis and pain), cerebral stimulant stored in enterochromaffin cells of GI tract

39
Q

4 types of 5 HT receptors

A

1F – cerebral vasoconstriction (agonist for migraines)
2 – coronary artery and pulmonary vessel vasoconstriction with stimulation
3 – PNS – visceral pain; CNS – emesis, appetite, addiction, pain, and anxiety (antagonism for antiemetic)
4 – gastrokinesis (agonist to treat constipation, IBS)

40
Q

Serotonin 5-HT3 Receptor Antagonists are appropriate for what types of patients and not appropriate?

A

Chemotherapy induced NV, PONV (not effective in motion sickness)

41
Q

MOA: Block peripheral receptors on the intestinal vagal afferents and central receptors in the vomiting center, CTZ (vagal stimulation)

A

Serotonin 5-HT3 Receptor Antagonists

42
Q

what receptors do Serotonin 5-HT3 Receptor Antagonists NOT effect and why is this important?

A

NO effect on the dopamine, histamine, adrenergic, or muscarinic receptors (no Parkinsonian, restlessness, hypotension, or sedation)
MINIMAL SIDE EFFECTS

43
Q

examples of Serotonin 5-HT3 Receptor Antagonists

A

Ondansetron (Zofran) 4-8 mg (0.15mg/kg) IV
Dolasetron (Anzemet) 12.5 mg IV
Granisetron (Kytril) 1 mg (0.01 mg/kg) IV
Palonosetron (Aloxi) 0.075 mg IV

44
Q

Side effect Serotonin 5-HT3 Receptor Antagonists

A

: headache, constipation, theoretically cardiac arrhythmias (Anzemet)

45
Q

Limitation Serotonin 5-HT3 Receptor Antagonists

A

cost, prolonged QT interval

46
Q

MOA: Unknown mechanism – possibly inhibit prostaglandin synthesis centrally and control endorphin release

A

Corticosteroids

47
Q

Enhances the effectiveness of 5-HT3 antagonists (6-10 mg)

A

Corticosteroids

48
Q

Dexamethasone (Decadron) dose

A

0.15 mg/kg

49
Q

Limitations corticosteroids?

A

: (chronic therapy) interference with healing, immune suppression, ? avascular necrosis, increased blood glucose in diabetic and obese patients

50
Q

when should you give scopalamine patch?

A

prior to induction

51
Q

when should you give dexamethasone?

A

at induction, every other drug given towards the end

52
Q

Choice of antiemetic agent? 6 things

A

Risk factors
Patient factors – gender, age, medical status
Side effects
History – PONV, motion sickness
Cost – is cheaper really the most cost-effective choice?
Surgical procedure

53
Q

Guidelines

A

Identify patients at high risk
Reduce baseline risks of PONV
Use prophylaxis with high risk and, maybe, moderate risk patients
Use appropriate rescue treatment

54
Q

Use prophylaxis with high risk and, maybe, moderate risk patients by

A

Consider 5-HT3 antagonist + 2nd agent

55
Q

when can you give 5HT3 dose?

A

If within 6 hours, don’t redose with 5-HT3 antagonist – no additional benefit
If after 6 hours, repeat dose of 5-HT3 antagonist and second agent from different class.

56
Q

what is Neurokinin (NK1), Substance P

A

Substance P is the natural ligand of the neurokinin receptor found in the area postrema, nucleus of the solitary tract and afferent fibers of the vagus nerve

57
Q

Antagonist of the NK1 receptor
Approved by FDA for PONV prophylaxis
40 mg po one hour preop
[subtance P]

A

aprepitant (emend)

58
Q

Alternative Treatments

A

acupressure
hypnosis
propofol – 0.5 mg/kg or 10-15 mg (sub-induction dose)
Ephedrine – IM dose of 0.5 mg/kg = droperidol iv

Pharmacology 680 (19 decks)

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