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Gastrointestinal System > Antiemetic Drugs > Flashcards

Antiemetic Drugs Flashcards

1
Q

What is the emetic response?

A

A reflex brought about by activating the vomiting center either directly or indirectly

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2
Q

Where are the direct-acting stimuli that activate the vomiting center from?

A

The cerebral cortex (anticipation or fear)
Sensory organs (upsetting sights, noxious odors or pain)
Vestibular apparatus of the inner ear

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3
Q

What are the indirect stimuli that activate the vomiting center?

A

First activate the chemoreceptor trigger zone (CTZ) which in return activates the vomiting center

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4
Q

How does the activation of CTZ occur?

A

By signal from the stomach and the small intestine (traveling along the vagal afferents)

By the direct action of emetogenic compounds that are carried to the CTZ in the blood.

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5
Q

What are examples of emetogenic compounds?

A

Anticancer drugs
Opioids
Ipecac

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6
Q

What is the result of activation of the CTZ?

A

Once activated, the vomiting center signals the stomach, diaphragm, and abdominal muscles, resulting in a coordinated response of expulsion of gastric contents

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7
Q

What are the receptors involved in the activation of CTZ? (7)

A

Serotonin
Glucocorticoids
Substance P
Neurokinin 1
Dopamine
Acetylcholine
Histamine

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8
Q

What is the general MOA of antiemetics?

A

Blocking or activating or or more of the receptors

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9
Q

What is the prototype drug of serotonin antagonists?

A

Ondansetron

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10
Q

What is the prototype drug of glucocorticoids?

A

Dexamethasone

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11
Q

What is the prototype drug of substance P/ neurokinin-1 antagonist?

A

Aprepitant

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12
Q

What is the prototype drug of benzodiazepine?

A

Lorazepam

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13
Q

What is the prototype drug of dopamine antagonists?

A

Prochlorperazine

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14
Q

What is the prototype drug of cannabinoids?

A

Dronabinol

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15
Q

What is chemotherapy-induced nausea and vomiting? (CINV)

A

Nausea and vomiting due to dehydration, electrolyte imbalances, nutrient depletion and esophageal tears

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16
Q

What is the main drawback of CINV?

A

It can be so serious that patients may discontinue therapy rather than endure further discomfort

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17
Q

What are three types of emesis associated with chemotherapy?

A

Anticipatory
Acute
Delayed

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18
Q

What is the mechanism of CINV?

A

Chemotherapy –> indirect and direct way of activating vomiting center–> serotonin release (GIT) / substance P (CTZ) –> 5-HT3 receptors/NK1 receptors –> CINV

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19
Q

What is the anticipatory emesis from chemotherapy?

A

Occurs before drugs are actually given, triggered by the memory of severe nausea and vomiting

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20
Q

What is the acute emesis from chemotehrapy?

A

Begins within minutes to a few hours after receiving chemotherapy and often resolves within 24 hours

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21
Q

What is the delayed emesis form chemotherapy?

A

Develops a day or more after drug administration

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22
Q

What is an example of delayed emetic drug?

A

Cisplatin emesis is maximal 48 to 72 hours after dosing and can persist for 6 to 7 days

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23
Q

What are antiemetics most effective for?

A

Most effective at preventing CINV rather than suppressing it once it has already begun

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24
Q

What does the antiemetic regimen depend on?

A

On the emetogenic potential of the chemotherapy drugs used:
If highly emetogenic –> 3 drugs
If moderately emetogenic –> 2 drugs
If barely emetogenic –> 1 drug

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25
Q

Which are the most effective drugs at suppressing nausea and vomiting caused by anticancer drugs?

A

Serotonin receptor antagonists

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26
Q

What are serotonin receptor antagonists effective against?

A

Nausea and vomiting associated with radiation therapy, anesthesia, viral gatsritis and pregnancy

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27
Q

What are the examples of serotonin receptor antagonists?

A

Ondansetron (prototype)
Granisetron (10 to 15x more potent than prototype)
Dolasetron
Palonosetron

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28
Q

What is Ondansetron approved for?

A

CINV
Vomiting associated with radiation therapy and anesthesia
Used off-label for other causes

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29
Q

What other causes is Ondansetron used for?

A

Childhood viral gastritis and morning sickness of pregnancy

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30
Q

What is the MOA of Ondansetron?

A

Blocks type 3 serotonin in CTZ and on afferent vagal neurons in the upper GIT

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31
Q

What is the effectiveness of Ondansetron like?

A

Very effective by itself, and even more effective when combined with dexamethasone

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32
Q

What is the administration route of Ondansetron?

A

Oral or parenteral

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33
Q

What are the side effects of Ondansetron?

A

Headache, diarrhea, dizziness
QT interval prolongation and increased risk of Torsades de Pointes

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34
Q

Why does Ondansetron not cause extrapyramidal effects?

A

It does not block the dopamine receptors

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35
Q

What are the extrapyramidal effects?

A

Akathisia, acute dystonia

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36
Q

Which kind of drugs cause extrapyramidal effects?

A

Antiemetic phenothiazines

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37
Q

What is the MOA of Granisetron?

A

Blocks 5-HT3 receptors on afferent vagal neurons and in the CTZ

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38
Q

What is Granisetron approved for?

A

Nausea and vomiting associated with radiation therapy, chemotherapy, and surgery

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39
Q

What are the adverse effects of Granisetron?

A

Headache, weakness, tiredness and diarrhea/constipation

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40
Q

What is the administration route of Granisetron?

A

PO
IV
Transdermal

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41
Q

What is Dolasetron approved for?

A

CINV and postoperative nausea and vomiting

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42
Q

What is the administration route of Dolasetron?

A

PO
IV

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43
Q

What are the side effects of Dolasetron?

A

Same as the other serotonin antagonists

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44
Q

What is the important exception when it comes to Dolasetron?

A

When given in high doses (IV), it poses a significant risk of fatal dysrhythmias

High dose - IV therapy should not be used, oral therapy and low-dose IV therapies are considered safe

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45
Q

What is Palonosetron?

A

A second generation serotonin antagonist

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46
Q

What is Palonosetron approved for?

A

CINV and postoperative nausea and vomiting

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47
Q

What is the MOA of Palonosetron?

A

Same mechanism, efficacy, and side effects as the rest of the serotonin antagonists

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48
Q

What are the two main differences of Palonosetron?

A

Has a much longer half-life
Effective against delayed emesis (as well as acute emesis ), whereas the others are most effective against acute emesis

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49
Q

What is the half-life of Palonosetron?

A

40 hours compared to the 8 hours (another serotonin antagonist)

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50
Q

Why is Palonosetron more effective against delayed emesis?

A

Due to its longer half-life

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51
Q

What are the administration routes of Palonosetron?

A

PO
IV

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52
Q

What are the glucocorticoids used to suppress CINV?

A

Methylprednisolone
Dexamethasone

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53
Q

How are glucocorticoids effective in suppressing CINV?

A

Both on their own and in combination with antiemetics

54
Q

What is the MOA of glucocrticoids?

A

They bind to the membrane, fuse, and transcribe multiple genes, the mechanism which affects and suppresses emesis though is unknown

55
Q

What is the administration route of glucocorticoids?

A

IV

56
Q

What are the side effects of glucocorticoids?

A

Serious side effects are absent; antiemetic use is intermittent and short-term

57
Q

When do serious side effects present with glucocorticoids?

A

If there is chronic use

58
Q

What are the examples of Substance P/ neurokinin 1 antagonists?

A

Aprepitant
Fosaprepitant
Rolapitant

59
Q

What is the prodrug of Substance P/ neurokinin 1 antagonists? What happens to it?

A

Fosaprepitant is the prodrug that undergoes conversion to Aprepitant in the body

60
Q

What is the principal application of Substance P/ neurokinin 1 antagonist?

A

Prevention of CINV

61
Q

What is the half life of Rolapitant?

A

180

62
Q

What is Rolapitant approved for and why?

A

Prevention of chemotherapy-induced delayed emesis because of its longer half-life

63
Q

What are the uses of Aprepitant?

A

Postoperative nausea and vomiting
CINV (delayed and acute)

64
Q

What is the MOA of Aprepitant?

A

Blocks neurokinin-1 receptors (for substance P) in the CTZ

65
Q

How can Aprepitant be used?

A

Alone for managing postoperative nausea nd vomiting
In combination with other antiemetic drugs for managing CINV

66
Q

Which other antiemetic drugs is Aprepitant used with?

A

Mainly glucocorticoids and serotonin antagonists

67
Q

What are the PK of Aprepitant?

A

Well absorbed
Plasma levels peak after 4 hours
Extensive hepatic metabolism - primarily CYP3A4, excretion in urine and feaces
Plasma half-life 9 to 13 hrs

68
Q

What are the adverse effects of Aprepitant?

A

Generally well tolerated
Fatigue and asthenia
Hiccups
Dizziness
Diarrhea
Milf, transient elevation of circulating aminotransferases, indicating possible liver injury

69
Q

What are the drug interactions of Aprepitant like?

A

It is a substance for, an inhibitor of, and indices of CYP3A4, which means the drug itself can metabolize other cancer drugs

It can save patients from emesis but cancel out the effects of the cancer drugs

70
Q

What other drug-metabolizing enzyme does Aprepitant induce?

A

CYP2D6

71
Q

What is the effect of Aprepitant indicating CYP2D6?

A

Wafarin/ethinyl are 2D6 substrates, so inducing CYP2D6 eliminates their efficacy

72
Q

What is Fosaprepitant?

A

An IV prodrug that undergoes RAPID conversion to Aprepitant

73
Q

What are the indications of Fosaprepitant?

A

Preventing CINV ONLY
In contrast with Aprepitant which is also indicated for postoperative nausea and vomiting

74
Q

What are the adverse effects of Fosaprepitant?

A

Similar to Aprepitant PLUS pain and induration at the infusion site

75
Q

What is the example of Benzodiazepines?

A

Lorazepam

76
Q

How is Lorazepam used?

A

In combination therapies to suppress CINV, not used as monotherapy

77
Q

What are the 3 principal benefits of Lorazepam?

A

Sedation,
Suppression of anticipatory emesis
Production of enterograde amnesia

78
Q

How does the anterograde amnesia help with antiemetic drug compliance?

A

Helps control extrapyramidal reactions caused by phenothiazine antiemetics

79
Q

What is the contraindication of Lorazepam?

A

Pregnancy

80
Q

What are the examples of dopamine antgonists?

A

Phenothiazines
Butyrophenones
Metoclopramide

81
Q

What is the MOA of Phenothiazines?

A

Block dopamine two receptors in the CTZ

82
Q

What are Phenothiazines approved for?

A

Surgery, cancer chemotherapy, toxins

83
Q

What are the side effects of Phenothiazines?

A

Extrapyramidal reactions, anticholinergic effects, hypotension and sedation

84
Q

What are other uses of Phenothiazines?

A

Used in schizophrenia

85
Q

What is the most widely used antiemetic in young children?

A

Phenothiazines, Phenergan

86
Q

What are the dangers of Phenothiazines?

A

Respiratory depression and local tissue injury

87
Q

What is a safer alternative of Phenothiazines for antiemetics for children?

A

Ondansetron

88
Q

What is the contraindication of Phenothiazines?

A

Children under 2 years of age, and should be used with caution for children over 2.

Respiratory depression can be severe or fatal, sometimes

89
Q

What are examples of Butyrophenones?

A

Haloperidol & Droperidol

90
Q

What is the MOA of Butyrophenones?

A

Block dopamine 2 receptors in the CTZ

91
Q

What are Butyrophenones effective against?

A

Postoperative nausea and vomiting, emesis caused by cancer chemotherapy, radiation therapy, and toxins

92
Q

What are the potential side effects of Butyrophenones?

A

Similar to those of Phenothiazines PLUS QT prolongation

93
Q

Which Butyrophenone drug is associated with QT prolongation?

A

Droperidol

94
Q

What is the MOA of Metoclopramide?

A

Blocks dopamine 2 receptors in the CTZ

95
Q

What is Metoclopramide used for?

A

Suppresses postoperative nausea, vomiting, and emesis with anticancer drugs, opioids, toxins, and radiation therapy

96
Q

What are examples of cannabinoids?

A

Dronabinol
Nabilone

97
Q

Where and what are cannabinoids approved for?

A

US, medical use approval

98
Q

What are cannabinoids related to?

A

Marihuana

99
Q

What is the principal psychoactive agent in C. sativa (marijuana)?

A

Dranabinol

100
Q

What is Nabilone?

A

A synthetic derivative f dronabinol

101
Q

What is Sativex?

A

Combination of THC and cannabidiol
Available in Canada and UK for treating neuropathic pain

102
Q

What are the therapeutic uses of Cannabinoids?

A

Suppressing CINV, second-line

103
Q

What is the MOA of Cannabinoids?

A

Mechanism unknown, most likely via activating cannabinoid receptors in and around the vomiting center

104
Q

What kind of patients should Cannabinoids be reserved for?

A

Patients who are unresponsive to or intolerant of preferred agents

105
Q

What is Dronabinol approved of that Nabilone is not?

A

Stimulating appetite in patients with AIDS

106
Q

What are the adverse effects of cannabinoids?

A

Temporal disintegration, dissociation, depersonalization, and dysphoria

Tachycardia and hypotension

Drowsiness

Abuse potential

107
Q

What is the caution indication of Cannabinoids?

A

Should be used with caution when it comes to patients with CVD

108
Q

What are the contraindications of Cannabinoids?

A

Patinets with psychiatric disorders

109
Q

Why is there an abuse potential for Cannabinoids?

A

It mimics the subjective side effects of marijuana

110
Q

What is a more effective alternative to Dexamethasone and Palonosetron?

A

Aprepitant and Palonosetron

111
Q

When is nausea and vomiting in preganncy common?

A

During the first trimester

112
Q

What is hyperemesis gravidarum?

A

A severe form of NVP, characterized by dehydration, ketonuria, hypokalemia, and loss of 5% or more of body weight

113
Q

How can NVP be managed?

A

Both pharmacological and non-pharmacological interventions

114
Q

What are the non-drug intervention for NVP?

A

Eating small portions of food through the whole day
Avoiding foods, odors, and supplements that trigger NVP
Acupuncture and ginger (alternative treatments)

115
Q

What is the first-line therapy for NVP?

A

Two drug combination: doxylamine and vitamin B6

116
Q

What are the alternative pharmacological treatments for NVP?

A

Prochlorperazine
Metochlopramide
Ondansetron

117
Q

What si the last resort of pharmacological treatments for NVP?

A

Methylprednisolone but only after ten weeks of gestation

118
Q

What is the risk associated with Methylprednisolone?

A

Cleft lip risk increases

119
Q

What are the drugs for motion sickness?

A

Prophylactically:
1. Anticholinergic
2. Antihistamines

120
Q

What is motion sickness?

A

Can be caused by sea, air, car and space travel

121
Q

WHat are the symptoms of motion sickness?

A

Nausea, vomiting, pallor and cold sweats

122
Q

What is the example of anticholinergic drugs used for motion sickness?

A

Scopolamine

123
Q

What is Scopolamine?

A

A muscarinic antagonist, the most effective drug for the prevention and treatment of motion sickness

123
Q

What are the examples of antihistamines used for motion sickness?

A

Dimenhydrinate,
MAclizine,
Cyclizine

124
Q

What is the MOA of Scopalamine?

A

Suppresses nerve traffic in the neuronal pathway that connects the vestibular apparatus of the inner ear to the vomiting center

125
Q

What are the common side effects of Scopalamine?

A

Dry mouth, blurred vision, drowsiness, urinary retention, constipation and disorientation

126
Q

What is the MOA of antihistamines?

A

Blocks ACh receptors & histamine receptors, suppressing of motion sickness due to the blocking of H1R and muscarinic receptors in the neuronal pathway that connects the inner ear to the vomiting center

127
Q

What is the most prominent side effect of antihistamines for motion sickness?

A

Sedation –> results from blocking H1R

128
Q

What are other side effects of antihistamines?

A

Dry mouth, blurred vision, urinary retention, and constipation –> muscarinic receptors blocking

129
Q

Which is more effective, antihistamine or Scopolamine?

A

Scopolamine; sedation further limits antihistamines’ utility

130
Q
A

Gastrointestinal System (28 decks)

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