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GIT - Anti emetics

Q: What are some benzodiazepines used as anti-emetic agents?

Benzodiazepines include Lorazepam ( Ativan® ) and Diazepam ( Valium® ). They are anxiolytic agents that reduce anticipatory emesis. Diazepam is useful for treatment of vertigo.

Q: What are glucocorticoids used for in chemotherapy?

Glucocorticoids such as Dexamethasone and methylprednisolone are given I.V. and effectively suppress emesis in chemotherapy.

47 important questions on GIT - Anti emetics

What are some benzodiazepines used as anti-emetic agents?

Benzodiazepines include Lorazepam (Ativan®) and Diazepam (Valium®). They are anxiolytic agents that reduce anticipatory emesis. Diazepam is useful for treatment of vertigo.

What are cannabinoids used for in clinical settings?

Alternative agents used to control Cancer Induced Emesis (CIE).
CIE: demonstrated clinical benefit since 1985 to alleviate CIE.
Used for clients unable to use or respond to other Antiemetics.

What are glucocorticoids used for in chemotherapy?

Glucocorticoids such as Dexamethasone and methylprednisolone are given I.V. and effectively suppress emesis in chemotherapy.

What are some adverse effects of cannabinoids?

Sedation, mood changes, euphoria, drowsiness, nightmares, dry mouth, confusion, depersonalization, nightmares, incoordination, memory lapse, hypotension & tachycardia.

What is the mechanism of cannabinoids?

The mechanism of cannabinoids involves inhibiting the vomiting center through stimulation of CB1 cannabinoid receptors.

What are the clinical uses of muscarinic antagonists (anticholinergics)?

Motion sickness
Preoperative nausea & vomiting
They are not useful in treating nausea caused by chemotherapy

What is the drug of choice for motion sickness among muscarinic receptor antagonists?

Hyoscine (Scopolamine) is the drug of choice for motion sickness among muscarinic receptor antagonists.

What are the side effects of muscarinic antagonists (anticholinergics)?

Drowsiness
Dry mouth
Blurred vision (dilate pupils)
Constipation
Transdermal delivery of scopolamine via skin patch decreases the incidence

What are the clinical uses of Histamine H1 Receptor Antagonists?

Motion sickness and vertigo
Cyclizine, Meclizine, Promethazine (cause drowsiness)
Nosic®: combination of Doxylamine + B6 for pregnancy nausea
Ondansetron safe in first trimester

What is the mechanism of action for Scopolamine in treating motion sickness?

It reduces excitability and depresses conduction from the vestibular apparatus to the vomiting center.

What are some examples of Histamine H1 receptor antagonists?

Promethazine (Phenergan®) for emesis
Doxylamine, Cinnarizine (stugeron nausea vomiting due to motion sickness/vertigo)
Cyclizine

Why is Scopolamine preferred over Atropine?

Scopolamine is preferred over Atropine because it has a longer duration of action and a more pronounced selective CNS action.

What is the mechanism of action for Histamine H1 receptor antagonists?

They act by inhibiting histamine pathways of the vestibular apparatus.

What are the side effects of Histamine H1 Receptor Antagonists?

Side effects include sedation, dry mouth, and anticholinergic side effects.

Why are phenothiazines and butyrophenones contraindicated in Parkinson disease?

These agents are contraindicated in Parkinson disease because of their extrapyramidal effects.

What is droperidol associated with, and when should it be avoided?

Droperidol is associated with QT prolongation avoid in CVD.

Which drug is a 5HT3 antagonist safe only in the first trimester?

Ondansetron is a 5HT3 antagonist only safe in the first trimester.

What are the clinical uses of phenothiazines and butyrophenones?

Clinical uses include:

Chemotherapy-induced emesis (CIE)
Radiation-induced emesis (RIE)
Post-operative nausea & vomiting (PONV)

What are examples of phenothiazines and butyrophenones?

Phenothiazine: Examples include: Prochlorperazine
Butyrophenones: Domperidone, Droperidol I.V (etc)

What are the side effects of phenothiazines and butyrophenones?

Side effects include:

Cholinergic effects (e.g. drowsiness, dry mouth, blurred vision)
Extrapyramidal effects
Orthostatic hypotension

What are the clinical uses of Metoclopramide?

Clinical uses of Metoclopramide include:

Chemotherapy-induced nausea & vomiting
Narcotic-induced vomiting

What is the mechanism of action for phenothiazines and butyrophenones?

Block dopaminergic D2 receptors in the CTZ.
Inhibit peripheral transmission to the vomiting center.
Block α1-adrenoceptors.
Prochlorperazine also blocks muscarinic cholinoceptors.

What are the side effects of Metoclopramide?

Side effects of Metoclopramide include:

Sedation
Diarrhea
Extrapyramidal effects
Hyperprolactinemia

What type of derivative is Metoclopramide?

Metoclopramide is a benzamide derivative. It functions by blocking dopamine D2-receptors within the CTZ and increases sensitivity of GIT to action of ACh, enhancing GIT motility and gastric emptying.

What are examples of Benzamides used as Dopamine D2 receptor antagonists?

Examples of Benzamides include Metoclopramide (Plasil^®).

How does Metoclopramide affect the lower esophageal sphincter?

It increases the lower esophageal sphincter tone. Additionally, high doses antagonize 5-HT3 receptors in the vomiting center and GIT, contributing to its effects.

Name two Butyrophenones that act as Dopamine D2 receptor antagonists.

Butyrophenones include Domperidone (motilium^®) and Haloperidol (Haldol^®).

What are the clinical uses of Serotonin (5-HT3) receptor antagonists?

Used for chemotherapy-induced vomiting.
As 2nd line agents in post-operative nausea & vomiting.
Not effective for motion-sickness-induced nausea and vomiting.

What are examples of Serotonin (5-HT3) Receptor Antagonists?

Ondansetron (Emitino®)
Granisetron (Kytril®)
Dolasetron
Palonosetron (Aloxi®)

Why are Serotonin (5-HT3) receptor antagonists not effective for motion-sickness-induced nausea?

They are not effective because there are no 5-HT3 receptors in the vestibular center.

What is the largest group of drugs used as anti-emetics among Dopamine D2 receptor antagonists?

The largest group is Phenothiazines, including Chlorpromazine (Largactil^®), Prochlorperazine (Compazine^®), and Perphenazine (Trilafon^®).

What are the side effects of Serotonin (5-HT3) receptor antagonists?

Headache
Diarrhea
Dizziness
Fatigue
Mild constipation

Why are Phenothiazines not recommended as first-line treatment?

Phenothiazines are not recommended as first-line treatment because of extrapyramidal side effects.

What does pharmacologic intervention rely on regarding the vomiting center?

Intervention relies on inhibition of inputs to the CTZ or depression of the vomiting center. The vomiting center receives inputs from several sources:

Chemoreceptor trigger zone (CTZ)
Vestibular nuclei apparatus
Peripheral afferents from pharynx, GIT
Higher cortical centers (area of the cerebral cortex)

What is the mechanism of Serotonin (5-HT3) Receptor Antagonists?

These antagonists suppress emesis by blocking 5-HT3 receptors in the CTZ and nerve terminals in the upper GIT.

What initiates the cascade of vomiting?

The cascade begins by the CTZ receiving impulses induced by drugs and toxins. The vestibular nuclei are stimulated by motion. Receptors under the CTZ, including Dopamine and 5-HT3, are involved.

What is vomiting/emesis?

Vomiting/emesis is the expulsion of gastric contents through the oral cavity. It is controlled and coordinated by the vomiting reflex.

How do receptors contribute to the vomiting mechanism?

The stimulation of receptors under the CTZ; Dopamine, 5-HT3, and the vestibular nuclei stimulated by (Histamine, ACh) overall stimulate the vomiting center followed by stimulation of the GIT.

What role do antagonists to certain receptors play in antiemetic drugs?

Antagonists to the receptors below act as antiemetic drugs:

5HT3
D2
M1
H1
NK1

What controls and coordinates the vomiting reflex?

The vomiting reflex is controlled and coordinated by:

Vomiting center (VC) in the medulla
Chemoreceptor trigger zone (CTZ) near the medulla

What happens when GIT motor neurons are triggered during vomiting?

When triggered, GIT motor neurons respond by contraction of diaphragm, anterior abdominal muscles, & stomach; epiglottis closes; upward peristaltic movement then vomiting occurs.

What receptors are stimulated in the CTZ during emesis?

CTZ is stimulated by:
- D2, 5HT3, Opioid Receptors
- Triggered by cancer chemotherapy, opioids, and other chemical substances.

How do agonists to CB1 receptors function in relation to antiemetics?

Agonists to CB1 receptors act as antiemetics.

What is absent in the vestibular system related to vomiting?

The vestibular have no 5-HT3 receptors.

Which receptors are involved in the VC and what stimulates them?

VC receptors include:
- M1, 5HT3, H1, D2
- Stimulated by All (e.g., CTZ, Vestibular nuclei, Pharynx, GIT, Cerebral cortex).

How do vestibular nuclei contribute to emesis?

Vestibular Nuclei involve:
- M1, H1
- Related to sense of balance, orient & coordinate movement with balance.
- Emesis stimulated by motion (e.g., motion sickness).

What role does the pharynx and GIT play in emesis?

Pharynx, GIT involve:
- 5HT3
- Stimulated by radiotherapy, chemotherapy.
- Serotonin (5HT3) signals CTZ when throat of pharynx is irritated (gag reflex).

The question on the page originate from the summary of the following study material:

Phamarcology

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