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F. Gastrointestinal Drugs > 3. Drugs used in Nausea & Vomiting > Flashcards

3. Drugs used in Nausea & Vomiting Flashcards

1
Q

Drugs for nausea and vomiting

A
  1. Serotonin 5-HT3 antagonists
  2. Corticosteriods
  3. Neurokinin Receptor antagonists
  4. Dopamine receptor antagonists
  5. Muscarinic receptor antagonists
  6. H1 histamine receptor antagonists
  7. Benzodiazepines
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2
Q

Examples of Serotonin 5-HT3 antagonists

A
  1. Ondansetron (1st Gen)

2. Palonosetron (2nd Gen)

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3
Q

MOA of Serotonin 5-HT3 antagonists

A
  1. Act at 5-HT3 receptors primarily in the GIT
  2. CNS 5-HT3 receptors do not appear to play an important role in actions in nausea and vomiting
  3. Efficacy enhanced by combination with a corticosteroid and NK1-receptor antagonist
  4. Intravenously 30 min before or orally 1 hour before chemotherapy to prevention of acute chemotherapy-induced nausea and vomiting (CNIV)
  5. Generally not effective for delayed nausea and vomiting (>24 hr after chemotherapy)

Antagonise the 5-HT3 receptors in the visceral afferents and in the chemoreceptor trigger zone

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4
Q

Major concerns / adverse effects of serotonin 5-HT3 antagonists

A
  1. Eliminated by hepatic metabolism and renal and hepatic excretion
    - Generally dose reduction not required in elderly or patients with renal insufficiency
    - Dose reduction of Ondansetron may be required for patients with hepatic insufficiency
  2. Generally well-tolerated but may cause headache, dizziness and constipation
  3. Small risk of cardiac arrhythmia (prolongation of QT interval) with ondansetron
  4. Undergo P450 metabolism
    - Do not appear to interfere with metabolism of other drugs
    - But other drugs may reduce hepatic clearance of the 5-HT3 antagonists
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5
Q

Examples of corticosteroids

A
  1. Dexamethasone

2. Methylprednisolone

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6
Q

MOA of corticosteroids

A
  1. Mimic effects of cortisol
  2. Basis of antiemetic effect unknown
  3. Often used in combination with 5-HT3 antagonists to prevent acute and delayed vomiting (and to some extent nausea) in patients on moderately to highly emetogenic chemotherapy regimens
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7
Q

Major concerns / adverse effects of corticosteroids

A
  1. Unlikely to occur with short-term use
  2. Higher doses or longer-term use (> 2 weeks) may cause iatrogenic Cushing’s syndrome, including:
    • Redistribution of fat (rounded face)
    • Muscle wasting, dysphonia
    • Thinning of skin, easy bruising
    • Hyperglycaemia, later diabetes
    • Osteoporosis
    • Immunosuppression
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8
Q

Examples of neurokinin receptor antagonists (substance P antagonists)

A
  1. Aprepitant (oral)

2. Fosaprepitant

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9
Q

MOA of neurokinin receptor antagonists (substance P antagonists)

A
  1. Action at neurokinin 1 receptors in the chemoreceptor trigger zone of area postrema
  2. Used in combination with corticosteroid and 5-HT3 receptor antagonists to prevent acute and delayed vomiting (and to some extent nausea) caused by highly emitogenic chemotherapy
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10
Q

Major concerns / adverse effects of neurokinin receptor antagonists (substance P antagonists)

A
  1. Fatigue, dizziness, diarrhoea
  2. Metabolism by CYP3A4
    • Interaction with various chemotherapeutic agents (e.g. docetaxel, etoposide, irinotecan, imatinib, vinblastine)
    • Drugs that inhibit CYP3A4 may influence plasma levels e.g. ketoconazole, clarithromycin, ritonavir, verapamil
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11
Q

Examples of dopamine receptor antagonists

A

Metoclopramide

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12
Q

MOA of dopamine receptor antagonists

A
  1. Dopamine (especially D2) receptor antagonism in the chemoreceptor trigger zone
  2. Also used as prokinetics to stimulate GI motility
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13
Q

Major concerns / adverse effects of dopamine receptor antagonists

A
  1. Extrapyramidal side effects:
    - Restlessness, dystonias and parkinsonian symptoms
    - Elderly are especially susceptible
    - On long-term treatment irreversible tardive dyskinesia can develop
  2. Elevated prolactin levels can cause:
    - Galactorrhea, gynaecomastia, impotence and menstrual disorders
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14
Q

Example of muscarinic receptor antagonists

A

Hyoscine (scopolamine)

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15
Q

MOA of muscarinic receptor antagonist

A
  1. Muscarinic receptor antagonist → antagonise mACh receptors in the vestibular nuclei, nucleus of the solitary tract and vomiting centre
  2. Used for prevention of motion sickness
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16
Q

Major concerns / adverse effects of muscarinic receptor antagonist

A
  1. Anticholinergic (parasympatholytic) adverse effects:
    • Dry mouth, blurring of vision, constipation
  2. High incidence of adverse effects when given orally therefore often administered by transdermal patch
17
Q

Example of a mixed H1 histamine receptor & muscarinic receptor antagonist

A

Diphenhydramine

18
Q

MOA of diphenhydramine

A
  1. H1 histamine receptor antagonism → antagonise H1 receptors in the vestibular nuclei and nucleus of the solitary tract
  2. Muscarinic receptor antagonist → antagonise mACh receptors in the vestibular nuclei, nucleus of the solitary tract and vomiting centre
  3. Particularly useful for the treatment of motion sickness
  4. Sedative effects of diphenhydramine → useful in the treatment of emesis due to chemotherapy
19
Q

Examples of antipsychotics: mixed dopamine, muscarinic and/or histamine receptor antagonists

A
  1. Phenothiazines: prochlorperazine, promethazine
    - dopamine, muscarinic & histamine receptor antagonism
  2. Butyrophenones: Droperidol
    - dopamine receptor antagonism and weak histamine receptor antagonism
  3. Atypical antipsychotics → olanzapine (olanzapine controls CINV delayed-nausea with less EPS)
20
Q

Main concerns / adverse effects of antipsychotics

A
  1. Sedative (due to antihistaminergic effect)
  2. Extrapyramidal side-effects (EPS) (e.g. Parkinsonian motor adverse effects)
  3. Hypotension
  4. Droperidol: prolongation of the QT interval
21
Q

Antiemetics for low emetic risk group

A

Serotonin 5-HT3 antagonists OR Dexamethasone OR Dopamine receptor antagonist

22
Q

Antiemetics for moderate emetic risk group

A

Serotonin 5-HT3 antagonists + Dexamethasone

23
Q

Antiemetics for high emetic risk group

A

Serotonin 5-HT3 antagonists + Dexamethasone + Neurokinin 1 receptor antagonists

24
Q

Antiemetics for carboplatin

A

Serotonin 5-HT3 antagonists + Dexamethasone + Neurokinin 1 receptor antagonists

25
Q

Examples of benzodiazepines

A
  1. Lorazepam

2. Diazepam

26
Q

MOA of benzodiazepines

A
  1. Binding to allosteric site on GABAa receptors increases chloride conductance
  2. Anxiolytic
  3. Reduce anticipatory vomiting or vomiting caused by anxiety
27
Q

Major concerns / adverse effects of benzodiazepines

A
  1. Sedative/hypnotic
  2. Additive effects with other sedative drugs and CNS depressants e.g. antidepressants, alcohol and opioids
    - respiratory depression on overdose
  3. Avoid during pregnancy, esp. first trimester (risk of cleft palate)

F. Gastrointestinal Drugs (3 decks)

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