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Pharmacology I - CP > Antiemetics > Flashcards

Antiemetics Flashcards

1
Q

Percent in children that PONV occurs

A

25-39% in children over the age of 3

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2
Q

Increased anesthetic duration ____ risk

A

increases

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3
Q

At risk patients benefit from _____

A

one or more prophylactic measures

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4
Q

Risk factors for PONV

A

females, history of PONV or motion sickness, nonsmoker, younger, apprehension, gastroparesis, recent food ingestion

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5
Q

Surgical risk factors for PONV

A

increased duration of anesthesia, type of surgery: laparoscopy, eye, T&A, breast, GU/GYN, preop administered opioid, inhalational induction, volatile anesthetics, NO

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6
Q

each 30 minute increase in duration increases PONV risk by ____

A

60%

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7
Q

Postanesthetic related factors for PONV

A

ambulation, postural hypotension, uncontrolled pain, postop opioid administration, early oral intake, lower FiO2 concentration, reversal agents (neostigmine >2.5mg)

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8
Q

SAMBA guidelines

A
  1. identify pts at risk
  2. employ management strategies
  3. employ one or more prophylactic measures for moderate risk
  4. use multiple interventions for high risk
  5. administer antiemetic to kids at high risk
  6. provide antiemetic with PONV who did not receive prophylactic therapy or prophylaxis failed
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9
Q

Apfel score

A

risk score 0-4
3 or 4 high risk- use multi-modal strategy

female (1)
nonsmoker (1)
hx of PONV (1)
postop opioids (1)

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10
Q

What is the benefit of combination therapy?

A

Targets multiple receptors

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11
Q

What kind of agents should be used in combination therapy?

A

a rapid onset agent + longer duration of action agent

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12
Q

How can vomiting be triggered?

A

directly or indirectly

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13
Q

Direct pathways that trigger vomiting

A

noxious stimuli, toxins, drugs, irritants

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14
Q

Indirect pathways that trigger vomiting

A

stimulation of vomiting center in medulla oblongata

  • cerebral cortex/thalamus
  • vestibular apparatus
  • vagal afferent GI tracts
  • chemoreceptor trigger zone (CTZ)
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15
Q

What is significant about the chemoreceptor trigger zone?

A

it is close to the medulla in the floor of the 4th ventricle, not protected by BBB

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16
Q

Once activated, efferent motor nerves travel thru ___

A

CN V, VII, IX, X, XII, sympathetic, and spinal nerves to stimulate various parts of the body to trigger vomiting

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17
Q

What receptors are thought to be activated?

A
  • histamine
  • muscarinic
  • opioid
  • dopamine (D2)
  • 5-hydroxytryptamine (serotonin)
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18
Q

What is the most common class of antiemetics?

A

serotonin receptor antagonist

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19
Q

Which subtype of 5-HT receptor mediates vomiting and where is it found?

A

subtype 3; 5-HT3 receptor in the GI tract and brain (CTZ and NTS)

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20
Q

Trigger zone of serotonin activated by ___

A

anesthetics and opioids

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21
Q

Serotonin CV effects

A

vasoconstrictor, vasodilator effect in heart is endothelium dependent

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22
Q

Serotonin respiratory and GI effects

A

resp: increased airway resistance
gi: release of ACh in myenteric plexus increases peristalsis

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23
Q

What kind of receptors are 5- HT3?

A

gated Na+/K+ channels

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24
Q

When are the serotonin receptor antagonists best administered?

A

end of surgery

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25
Q

Example of a serotonin receptor antagonist

A

Ondansetron, Palonosetron, Dolasetron

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26
Q

Dose of Ondansetron

A

PO 4 or 8mg
IV 4mg
0.1 mg/kg if <40 kg (kids)

27
Q

Half life and onset time of Zofran

A

Half life: 4 hours

Onset: 30 minutes

28
Q

Metabolism of Zofran

A

liver by hydroxylation and conjugation

no need to adjust for renal

29
Q

Dose of Palonosetron

A
  1. 75 mg for PONV

0. 25 chemo-induced

30
Q

Half life of Palonosetron

A

40 hours

31
Q

Dose of Dolasetron

A

12.5 mg IV

32
Q

MOA of Dolasetron

A

reduce activity of vagus nerve to limit activation of the vomiting center in medulla oblongata

33
Q

When should you administer dolasetron?

A

within 15 minutes before the end of anesthesia

34
Q

Active metabolite of dolasetron

A

hydrodolasetron

35
Q

Droperiol is part of what class and MOA

A

butyrophenone/dopamine receptor antagonist

MOA: blocks dopamine receptors that contribute to development of PONV

36
Q

Dose of droperidol

A

0.625-1.25 mg IV or IM

37
Q

What does droperidol cause?

A

QT interval prolongation

38
Q

What class and MOA of prochlorperazine (compazine)

A

antipsychotic/antiemetic

MOA: affects multiple receptors - histaminergic, dopaminergic (D2 blockade), muscarinic

39
Q

Dose of compazine

A

5-10 mg IM/IV before induction

40
Q

What kind of side effects could prochlorperazine cause?

A

extrapyramidal and anticholinergic side effects (muscarinc side effects)

sedation, blurry vision, hypotension, dizziness, neuroleptic malignant syndrome, restlessness, dystonia

41
Q

What class is metoclopramide in and MOA?

A

dopamine receptor antagonist

MOA: centrally acting as dopamine receptor antagonist in CTZ, peripherally acting as cholinomimetic in GI tract

42
Q

Which antiemetic is a good choice for patients at risk of aspiration?

A

metoclopramide (reglan)

43
Q

Dose for metoclopramide

A

10 mg IV or 0.1 - 0.25 mg/kg q 6-8h

44
Q

When should reglan be avoided?

A

pheochromocytoma (can cause HTN crisis), parkinson’s, seizure, GI obstruction (can cause extrapyramidal effects)

45
Q

What class and MOA of Aprepitant (Emend)

A

neurokinin-1 receptor antagonist

MOA: NK-1 antagonist inhibit substance P at central and peripheral receptors

46
Q

Dosing considerations with Emend

A

want to decrease dose of zofran if given together because Emend increases activity of serotonin receptor antagonists

if administered with dexamethasone, reduce dose by half to keep dexamethasone concentrations

47
Q

Effects of Emend on oral contraceptives

A

makes ineffective for 28 days!

48
Q

MOA of dexamethasone (decadron)

A

long acting corticosteroid with anti-inflammatory and immunosuppressant properties

49
Q

Dose of Dexamethasone

A

4-10mg IV

peds: 0.2 - 0.5 mg/kg IV

50
Q

Contraindications with Dexamethasone

A

uncontrolled infections, known hypersensitivity, cerebral malaria, systemic fungal infection, concurrent treatment with live virus vaccine

51
Q

Class and MOA of Dimenhydrinate

A

histamine1 receptor antagonist

MOA: competes with histamine at H1 receptor sites in GI tract, blood vessels, and respiratory tract, blocks CTZ, depresses labyrinthine function and vestibular stimulation

52
Q

Dose of dimenhydrinate

A

50-100mg IV/IM q4h (max dose 100mg q4h)

53
Q

Promethazine MOA

A

antihistamine (H1 antagonist) and anticholinergic/muscarinic blocking effects

54
Q

Dose of promethazine

A

12.5-25 mg q4-6h
IM route preferred
low dose (5-10) for prophylaxis/rescue

55
Q

Class and MOA of Scopolamine

A

muscarinic antagonist/anticholinergic

inhibits action of Ach at parasympathetic sites in smooth muscle, CNS, and secretory glands, competitively blocks binding of ACh

56
Q

What allows anticholinergics to bind to Ach receptors?

A

ester linkage

57
Q

What can you give to reverse scopolamine?

A

physostigmine

0.01-0.03 mg/kg

58
Q

Dose of scopolamine

A

1.5 mg transdermal patch behind the ear the evening before surgery

59
Q

Adverse effects of scopolamine

A

dry mouth, increased thirst, dry skin, constipation, drowsy, dizzy, blurry, dilated pupils, light sensitive

60
Q

ephedrine dose

A

10-25mg IV for NV associated with postural hypotension
0.5 mg/kg IM at end of surgery = droperidol
40mcg/kg IM minimizes NV with less sedation

61
Q

Midazolam dose

A

peds: 50-75mcg/kg IV
adult: 2mg IV

62
Q

What is a good combination for midazolam in kids

A

midazolam + dexamethasone = zero incidence of PONV in kids undergoing strabismus surgery

63
Q

what nonpharmacological intervention can we use for NV?

A

P6 acupuncture point stimulation

isopropyl alcohol inhalation

Pharmacology I - CP (8 decks)

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