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GIT > Antiemetics > Flashcards

Antiemetics Flashcards

1
Q

What are 7 drug classes used as anti-emetics?

A

1) Serotonin 5-HT3 receptor antagonists
2) Corticosteroids
3) Neurokinin receptor antagonists
4) Dopamine receptor antagonists
5) Muscarinic receptor antagonists
6) Histamine H1 receptor antihistamines
7) Benzodiazepines

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2
Q

What are 4 sites that can trigger the vomiting center?

A

1) Chemoreceptor trigger zone (postrema area of 4th ventricle floor)

2) GIT (mechano/chemoreceptors)

3) Vestibular system

4) Higher centers of CNS

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3
Q

What are 3 examples of 5-HT3 serotonin antagonists (-setron)?

A

In order of T1/2
Ondansetron (4-9hr) < Granisetron (9-12hr) < Palonosetron (40-50hr)

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4
Q

How and how often is Odansetron administered?

A

Once daily (Oral/IV)

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5
Q

What is the moa of 5-HT3 serotonin antagonists?

A

Blocks 5-HT receptors on afferent dorsal root nerve primarily in the GIT (CNS 5-HT receptors not impt for nausea/vomiting)
→ block transmission of signals of distension and noxious stimuli from GIT to CNS

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6
Q

When are 5-HT3 antagonists given for chemotherapy-induced vomiting?

A

IV 30mins before / Oral 1 hr before

(not effective >24 hours/delayed)

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7
Q

What are drug classes that are combined with 5-HT antagonists to increase its efficacy?

A

Corticosteroids
NK1-receptor antagonists

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8
Q

Which 5-HT3 antagonist is associated with a small risk of orofacial malformations in early pregnancy?

A

Odansetron

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9
Q

In which px should 5-HT3 antagonists be avoided/used in caution?

A

1) px with cardiac anomalies (prolong QT interval)
2) px on other drugs that prolong QT interval
3) early pregnancy (odansetron → orofacial malformation)

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10
Q

How are 5-HT3 antagonists metabolised?

A

CYP450

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11
Q

What are 3 common AEs of 5-HT3 antagonists?

A

1) Headaches
2) Dizziness
3) Drowsiness
4) Constipation or diarrhoea

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12
Q

5-HT3 antagonists have a small risk of inducing ____________ as a AE?

A

Cardiac arrythmias (prolong QT interval)

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13
Q

What are 2 examples of corticosteroids used as anti-emetics?

A

Dexamethasone
Methylprednisolone

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14
Q

What is the main concern of long term (> 2 wks) use of corticosteroids as anti-emetics?

A

Iatrogenic Cushing’s syndrome

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15
Q

What drugs are used with corticosteroids as anti-emetics?

A

5-HT3 antagonists for acute and delayed chemotherapy-induced vomiting

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16
Q

What is an example of a substituted benzamide used as a anti-emetic?

A

Metoclopramide

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17
Q

What is the moa of substituted benzamide?

A

1) Dopamine (esp D2) receptor antagonism @ chemoreceptor trigger zone (CTZ)
2) Prokinetic → stimulate GI motility (except in complete obstruction)

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18
Q

What are 2 AEs of substituted benzamines used as anti-emetics?

A

1) Extrapyramidal symptoms → parkinsonian symptoms (eg. bradykinesia, restlessness, tremor) + tardative dyskinesia (LT treatment)
- elderly esp susceptible

2) Elevated prolactin → galactorrhea, menstrual disorders, gynaecomastia, impotence

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19
Q

What are 2 examples of Neurokinin Receptor/Substance P Antagonists used as anti-emetics (-prepitant)?

A

1) Aprepitant (Oral)
2) Fosaprepitant (IV → converted to aprepitant in 30mins)

20
Q

What is the moa of substance P/NK antagonists?

A

Antagonise Neurokinin 1 receptors in area postrema (CNS)

21
Q

What drugs are used with NK/substance P antagonists as anti-emetics?

A

Corticosteroids
5-HT3 receptor antagonists

22
Q

What are 6 AEs of NK antagonists?

A

Common:
1) Fatigue
2) Hiccups
3) Diarrhoea/constipation

Severe:
1) Peripheral neuropathy
2) blood dyscrasias

23
Q

How are NK antagonists metabolised?

A

Hepatic CYP3A4
(DDI with chemotherapy, CYP3A4 inhibitors eg. ketoconazole, clarithromycin, ritonavir, verapamil)

24
Q

What are 4 drug classes used for acute chemotherapy-induced nausea?

A

1) 5-HT3 antagonist (eg. Odansetron)
2) Corticosteroids (eg. dexamethasone)
3) NK1 antagonists (eg. aprepitant)
4) Olanzapine (Atypical antipsychotic)
5) Dopamine receptor antagonist (eg. metoclopramide)

25
Q

What are 4 drug classes used for acute chemotherapy-induced nausea?

A

1) Corticosteroids (eg. dexamethasone)
2) Olanzapine (Atypical antipsychotic)
3) Metoclopramide
4) Aprepitant

26
Q

What are 4 examples of antipsychotics used as anti-emetics?

A

Phenothiazines: Dopamine, muscarinic antagonist, antihistamine
1) Promethazine
2) Prochlorperazine

Butyrophenones: dopamine antagonism, weak antihistamine
3) Droperidol

Atypical antipsychotic:
4) Olanzapine

27
Q

What are the moas for antipsychotics used as anti-emetics?

A

1) Dopamine receptor antagonism (CTZ)
2) Muscarinic antagonism (Vestibular system & vomiting center)
3) Antihistamine (Vestibular system & vomiting center)

28
Q

What are 4 AEs of antipsychotics used as anti-emetics?

A

1) Sedative (antihistaminergic effects)
2) Extrapyramidal syndrome
3) Hypotension
4) Prolonged QT interval (Properidol)

29
Q

Muscarinic receptor antagonism has additional ____________ effect when used as a anti-emetic?

A

Antispasmodic

30
Q

Olanzapine controls CINV delayed-nausea with less ___________.

A

Extrapyramidal syndrome

31
Q

Which anti-emetics are used for prevention of nausea by noxious GIT stimulation (eg. small-bowel obstruction)?

A

1) 5-HT3 Antagonist (-setron)
2) Promethazine
3) Prochlorperazine

32
Q

Which anti-emetics are used to prevent anticipatory nausea and vomiting?

A

1) Benzodiazepines (-zepams)
2) Anticholinergic (eg. hyoscine)
3) Mixed H1 antihistamine and muscarinic receptor antagonists (eg. cinnarizine, diphenhydramine)

33
Q

What are 2 examples of benzodiazepines used as anti-emetics?

A

1) Lorazepam
2) Diazepam

34
Q

What is the moa of benzodiazepines used as anti-emetics?

A

1) Allosteric inhibition of GABA receptors → ↑Cl conductance
2) Anxiolytic
3) ↓ anticipatory/anxiety-induced vomiting

35
Q

What are 2 AEs of benzodiazepines used as anti-emetics?

A

1) Sedative/hypnotics
2) Additive effects on CNS depressants (respi depression)

36
Q

In which px should benzodiazepines be avoided?

A

Pregnant (esp 1st trimester)
- risk of cleft palate

37
Q

What is an example of an anticholinergic used as an anti-emetic?

A

Hyoscine

38
Q

What are 2 AEs of anticholinergics used as anti-emetics?

A

1) PNS-lytic (eg. xerostomia, vision blur)
2) CNS (eg. sedation, confusion)

39
Q

Which anti-emetic can also be used as an antispasmodic for abdominal cramps?

A

Anticholinergic (hyoscine)

40
Q

What are 2 examples of mixed H1 antihistamine and muscarinic receptor antagonists used as anti-emetics?

A

1) Cinnarizine
2) Diphenhydramine

41
Q

Which anti-emetics are particularly useful in the treatment of motion sickness?

A

Diphenhydramine
Cinnarizine

42
Q

The sedative effects of diphenhydramine is also useful in treating emesis due to ____________.

A

chemotherapy

43
Q

What are 2 AEs of mixed H1 antihistamine and muscarinic receptor antagonists used as anti-emetics?

A

1) Sedative (H1 antagonism)
2) PNS-lytic (eg. xerostomia, blurring vision, constipation)

44
Q

In which 2 demographics should anti-emetics generally be avoided?

A

Pregnant women
Infants/children

45
Q

How is nausea and vomiting managed in pregnancy?

A

1) Dietary changes
- avoid empty/overly full
- Avoid coffee, odourus, high-fat, acidic, very sweet foods
- Choose high-protein, salty, low-fat, bland, dry foods
- Sip fluid/take fluids 30min before solid food
- Avoid noxious triggers
- Take ginger-containing foods

2) Pharmacotherapy
- Only if dietary dont work
- Pyridoxine (vit B6) supplements
- Doxylamine (if pyridoxine dont work coz 1st gen antihistamine → AE on pregnancy/fetal development

46
Q

What are 3 pharmacotherapies used for persistent nausea and vomiting in children?

A

1) Gastroparesis
- prokinetic (eg. metoclopramide)

2) Post-op
- 5-HT3 antagonists

3) Chemo
- 5-HT3 antagonists
- NK1 antagonists

GIT (14 decks)

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