Antiemetics and Nausea Management
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Questions and Answers

Which of the following is a primary use for certain antiemetics, other than preventing nausea and vomiting caused by chemotherapy?

  • As a prokinetic agent. (correct)
  • Reducing tachycardia.
  • Treating arrhythmias.
  • Dilating pupils.

A patient who is on an antiemetic and also has a pre-existing condition of congestive heart failure should avoid treatment with which of the following medications?

  • Olanzapine
  • Amisulpride (correct)
  • Nabilone
  • Scopolamine

What is a key mechanism of action for the antiemetic drug class of Cannabinoids?

  • Stimulating cannabinoid CB1 receptors in the brainstem DVC and GIT. (correct)
  • Acting as a D2 antagonist in the brainstem.
  • Blocking muscarinic receptors in the DVC.
  • Blocking dopamine D1,2,3,4 receptors.

Which of the following side effects is NOT commonly associated with antimuscarinic medications?

<p>Hypotension (D)</p> Signup and view all the answers

What is a significant metabolic characteristic of Olanzapine?

<p>More than 40% is removed by hepatic first-pass effect. (C)</p> Signup and view all the answers

Which of the following is a primary use for histamine H1 receptor antagonists?

<p>Motion sickness (B)</p> Signup and view all the answers

The mechanism of action of dopamine D2 receptor antagonists involves the DVC's:

<p>Blocking of dopamine D2 receptors (A)</p> Signup and view all the answers

Which of the following side effects is most likely to occur when taking promethazine?

<p>Drowsiness (B)</p> Signup and view all the answers

Which of the following drugs has been associated with fatal cardiac arrythmias?

<p>Droperidol (B)</p> Signup and view all the answers

What condition is haloperidol used to treat?

<p>Cannabinoid hyperemesis syndrome (C)</p> Signup and view all the answers

A patient experiences restlessness and an inability to sit still after being administered an antiemetic. Which of the following adverse effects is most likely causing this?

<p>Akathisia (C)</p> Signup and view all the answers

A patient is experiencing vomiting due to a viral gastroenteritis. Which of the following medications is least appropriate for this condition?

<p>Dimenhydrinate (D)</p> Signup and view all the answers

Which of the following medications blocks both serotonin 5-HT3 and dopamine D2 receptors?

<p>Metoclopramide (B)</p> Signup and view all the answers

Which of the following best describes the primary mechanism of first-generation 5-HT3 receptor antagonists in managing chemotherapy-induced nausea and vomiting (CINV)?

<p>They primarily attenuate the immediate phase of CINV by blocking serotonin receptors. (A)</p> Signup and view all the answers

What is the particular advantage of palonosetron over first-generation 5-HT3 receptor antagonists in managing CINV?

<p>Palonosetron more potently attenuates both phases of CINV due to its higher affinity and additional effects, including receptor internalization. (D)</p> Signup and view all the answers

What is the rationale for using larger doses of 5-HT3 receptor antagonists intravenously, as indicated in the text?

<p>To combat emesis induced by highly emetogenic cancer chemotherapeutics, where oral doses might not be sufficient. (B)</p> Signup and view all the answers

What does the term 'triple prophylactic therapy' refer to regarding CINV management?

<p>The combined use of a 5-HT3 receptor antagonist, dexamethasone, and an NK1 receptor antagonist. (D)</p> Signup and view all the answers

How does the drug netupitant contribute to the management of CINV when combined with palonosetron?

<p>Netupitant is a second-generation NK1 receptor antagonist that works in combination with palonosetron for prophylactic CINV antiemetic therapy. (A)</p> Signup and view all the answers

Which of the following is a common adverse effect of 5-HT3 receptor antagonists?

<p>Headache (B)</p> Signup and view all the answers

Which of these 5-HT3 receptor antagonists has the longest half-life?

<p>Palonosetron (B)</p> Signup and view all the answers

Which enzyme primarily metabolizes granisetron?

<p>CYP1A1 (C)</p> Signup and view all the answers

Which of the following mechanisms is associated with the action of NK1 receptor antagonists, in relation to Substance P?

<p>Prevent Substance P from exciting its receptors. (B)</p> Signup and view all the answers

Which of the following is a symptom of serotonin syndrome?

<p>Muscle rigidity (D)</p> Signup and view all the answers

Which class of antiemetic is most effective against the delayed phase of chemotherapy-induced nausea and vomiting (CINV)?

<p>NK1 receptor antagonists (B)</p> Signup and view all the answers

What is a potential consequence of combining 5-HT3 receptor antagonists with selective serotonin reuptake inhibitors?

<p>Serotonin syndrome (B)</p> Signup and view all the answers

Which of these statements is TRUE for 5-HT3 receptor antagonists?

<p>They exhibit moderate plasma protein binding. (A)</p> Signup and view all the answers

Which of the following is NOT a primary location of emetic loci in the brainstem?

<p>Cerebral cortex (A)</p> Signup and view all the answers

What is the primary neurotransmitter found within enterochromaffin (EC) cells of the gastrointestinal tract, that plays a role in the emetic response?

<p>Serotonin (5-HT) (A)</p> Signup and view all the answers

Which of these mechanisms is MOST directly involved in relaying emetic stimuli from the brainstem to the gastrointestinal tract (GIT)?

<p>Dorsal motor nucleus of the vagus (DMNX) (A)</p> Signup and view all the answers

Which receptor type, found in the area postrema (AP), is associated with the binding of serotonin, an important emetic neurotransmitter?

<p>5-HT3 (C)</p> Signup and view all the answers

Which of the following is a feature of the Central Pattern Generator (CPG)?

<p>Directly involved in the motor pattern of emesis (B)</p> Signup and view all the answers

What is the effect of emetogens on the central/peripheral emetic loci?

<p>Activate central and/or peripheral emetic loci (A)</p> Signup and view all the answers

Which of the following is NOT a recognized cause of the release of emetic neurotransmitters?

<p>Pain (A)</p> Signup and view all the answers

Where are the receptors involved in mediating nausea mainly located?

<p>Higher brain centers such as cerebral cortex (D)</p> Signup and view all the answers

Which of the following factors influence the choice of antiemetic medication?

<p>Underlying cause of nausea/vomiting (A)</p> Signup and view all the answers

What distinguishes the action of most antiemetics?

<p>They are primarily antagonists at emetic receptors (C)</p> Signup and view all the answers

According to the information provided, which of the following is NOT typically associated with NK1 receptor antagonists?

<p>Elevated Blood Pressure (A)</p> Signup and view all the answers

What is the primary neurotransmitter released in the gut tissue during the early phase of chemotherapy-induced nausea and vomiting (CINV), according to traditional understanding?

<p>Serotonin (A)</p> Signup and view all the answers

According to traditional understanding, what is the primary neurotransmitter released in the brainstem during the delayed phase of CINV?

<p>Substance P (D)</p> Signup and view all the answers

According to more recent findings, what is the nature of neurotransmitter release during both the early and delayed phases of CINV?

<p>Concomitant release of several neurotransmitters including serotonin, substance P, and dopamine. (D)</p> Signup and view all the answers

Metoclopramide is described as having which of the following pharmacological actions?

<p>Dopamine D2 receptor and 5-HT3 receptor antagonist (D)</p> Signup and view all the answers

Which of the following is a known effect of the antiemetic olanzapine?

<p>Reduces nausea and vomiting caused by chemotherapeutics. (B)</p> Signup and view all the answers

What is a potential cause of infusion site reactions following intravenous administration of NK1 receptor antagonists?

<p>Formulation ingredients of the drug itself (C)</p> Signup and view all the answers

According to the content, which of the following is a common side effect of NK1 receptor antagonists?

<p>Constipation (D)</p> Signup and view all the answers

Flashcards

Antiemetics

Drugs that prevent or reduce nausea and vomiting.

Antimuscarinics

A class of antiemetics that block muscarinic receptors in the brainstem's DVC, effectively preventing the signals that trigger nausea.

Scopolamine

A specific antimuscarinic drug highly effective against motion sickness. It works by blocking muscarinic receptors in the brainstem's DVC, suppressing the nausea response.

Amisulpride

A benzamide with D2 antagonist properties used for post-operative nausea and vomiting (PONV). It works by blocking dopamine receptors, reducing the signals associated with nausea.

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Olanzapine

A second-generation antipsychotic that blocks dopamine and serotonin receptors in the brain. It's used to prevent chemotherapy-induced nausea and vomiting, both acute and delayed.

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Histamine H1 Receptor Antagonist

A drug that blocks the action of histamine at H1 receptors, often used for motion sickness and vertigo.

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Dorsal Vagal Complex (DVC)

The area in the brainstem that receives signals from the inner ear and CTZ and is involved in regulating vomiting.

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Chemoreceptor Trigger Zone (CTZ)

A region in the brain that detects toxic substances and triggers the vomiting reflex.

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Dopamine D2 Receptor Antagonists

A group of medications that block dopamine receptors, particularly in the CTZ, to prevent nausea and vomiting.

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Metoclopramide

A medication that blocks both serotonin 5-HT3 and dopamine D2 receptors, used for nausea and vomiting.

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Dystonia

A type of involuntary muscle movement disorder that can be a side effect of some antiemetics.

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Tardive Dyskinesia

A type of involuntary movement disorder that can be a side effect of long-term use of some antiemetics.

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5-HT3 Receptor Antagonists

A type of drug that blocks serotonin receptors (5-HT3R) in the gut and brain, reducing nausea and vomiting caused by chemotherapy.

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Ondansetron

The first generation 5-HT3 receptor antagonist, known for its effectiveness in reducing the initial phase of chemotherapy-induced nausea and vomiting (CINV).

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Palonosetron

A second generation 5-HT3 antagonist with stronger and longer-lasting effects than ondansetron, affecting both the initial and delayed phases of CINV.

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Triple Prophylactic Therapy

The combination of a 5-HT3 antagonist, a corticosteroid (dexamethasone), and a NK1 receptor antagonist used to prevent both early and delayed nausea and vomiting.

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NEPA

A medication combining palonosetron (a 5-HT3 antagonist) and netupitant (a NK1 receptor antagonist), taken orally to prevent chemotherapy-induced nausea and vomiting.

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What is the emetic reflex?

Emetic reflex refers to the complex physiological process that leads to vomiting. It involves various brain regions, peripheral nerves, and chemical signals.

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What is CINV?

Chemotherapy-induced nausea and vomiting (CINV) is a common side effect of cancer treatment characterized by feelings of sickness and urge to vomit.

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What are emetic neurotransmitters?

Emetic neurotransmitters are chemical messengers involved in triggering vomiting. Key examples include serotonin (5-HT), dopamine (DA), substance P (SP), prostaglandins, and leukotrienes.

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What is the dorsal vagal complex (DVC) and what does it do?

The dorsal vagal complex (DVC) in the brainstem is a crucial brain region involved in the emetic reflex. It contains several important areas like the area postrema (AP) and the nucleus tractus solitarius (NTS).

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What is the area postrema (AP) and where is it located?

The area postrema (AP) is located in the chemoreceptor trigger zone (CTZ), a region in the brain sensitive to toxins and chemicals. The AP plays a vital role in initiating vomiting by sensing dangerous substances in the body.

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What is the nucleus tractus solitarius (NTS) and what does it do?

The nucleus tractus solitarius (NTS) is a brain region that receives sensory information from the gastrointestinal tract and other areas. It integrates this information and transmits signals to other brain regions involved in vomiting.

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What are enterochromaffin cells (EC) and what do they contain?

Enterochromaffin cells (EC) are specialized cells found in the gastrointestinal tract (GIT). They contain serotonin (5-HT) and other substances that can contribute to vomiting.

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What is the vagus nerve's role in vomiting?

The vagus nerve connects the brain to the gastrointestinal tract. It plays a crucial role in the emetic reflex, transmitting signals about nausea and vomiting.

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What are antiemetics and how do they work?

Antiemetics are medications used to prevent or treat nausea and vomiting. They work by blocking the action of emetic neurotransmitters or affecting the brain regions involved in the emetic reflex.

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Why do different antiemetics work better for different types of vomiting?

The effectiveness of antiemetics varies depending on the cause of nausea and vomiting. There is no single antiemetic universally effective for all types of vomiting.

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Neurokinin NK1 Receptor Antagonists

Drugs that block the neurokinin NK1 receptor, primarily used to manage chemotherapy-induced nausea and vomiting (CINV).

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Fatigue and Asthenia

A common side effect of neurokinin NK1 receptor antagonists, characterized by tiredness and weakness.

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Infusion Site Reactions

A side effect of neurokinin NK1 receptor antagonists, often occurring after intravenous administration.

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Serotonin Release in Early CINV

The theory that serotonin is the main neurotransmitter responsible for early CINV.

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Substance P Release in Delayed CINV

The theory that substance P is the main neurotransmitter responsible for delayed CINV.

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Multiple Emetic Neurotransmitters

The understanding that multiple neurotransmitters, including serotonin and substance P, along with dopamine, prostaglandins, and leukotrienes, contribute to both early and delayed CINV.

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Metoclopramide's Antiemetic Action

A drug that blocks both dopamine D2 receptors and serotonin 5-HT3 receptors, commonly used to manage CINV.

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Olanzapine: Anti-Nausea Actions

A second-generation antipsychotic that blocks dopamine and serotonin receptors, effective against CINV.

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Half-Life of 5-HT3 Antagonists

The half-life refers to the time it takes for the concentration of a drug in the body to reduce by half. For 5-HT3 receptor antagonists, the half-life varies, but generally lasts longer than the drug's duration of action.

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Serotonin Syndrome

Serotonin syndrome is a potentially life-threatening condition that occurs when 5-HT3 receptor antagonists are combined with selective serotonin reuptake inhibitors (SSRIs). It results from an excess of serotonin in the body.

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NK1 Receptor Antagonists

NK1 receptor antagonists selectively block the action of Substance P, a neurotransmitter that triggers nausea and vomiting.

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Substance P and Neurokinin Receptors

Substance P binds and activates three types of neurokinin receptors: NK1, NK2, and NK3. NK1 receptors, found in the gut and brainstem, are key targets for antiemetic drugs.

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NK1 Receptor Antagonists and CINV

NK1 receptor antagonists like Apripitant, Netupitant, and Rolapitant are highly effective against the delayed-phase of CINV (chemotherapy-induced nausea and vomiting).

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Mechanism of NK1 Receptor Antagonists

NK1 receptor antagonists work by reversibly binding to NK1 receptors, preventing Substance P from activating them and triggering vomiting.

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Combination Therapy for CINV

Combining an NK1 receptor antagonist with a dual therapy of a 5-HT3 antagonist and dexamethasone provides greater protection against CINV.

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Study Notes

Antiemetics

  • Antiemetics are drugs used to treat nausea and vomiting.
  • Not all antiemetics work for all types of vomiting.
  • Some antiemetics are agonists, while most are antagonists.

Objectives

  • Discuss neuroanatomy of vomiting.
  • Discuss the neuroanatomy and receptor mechanisms of emetic neurotransmitters.
  • Determine if currently used antiemetics reduce nausea.
  • Understand pharmacology and mechanisms of antiemetic actions, and clinical uses of emetrol, anti-muscarinics, anti-histamines, dopamine D₂ antagonists, metoclopramide, cannabinoids, and olanzapine.
  • Discuss pharmacology and clinical application of first- and second-generation serotonin 5-HT₃ receptor antagonist antiemetics.
  • Discuss pharmacology and clinical application of substance P neurokinin NK₁ receptor antagonist antiemetics.
  • Describe acute and delayed phases of chemotherapy-induced nausea and vomiting and prophylactic antiemetic therapy.

Nausea and Vomiting (Emesis)

  • Nausea is an unpleasant feeling of imminent vomiting.
  • Its neurochemistry and neuroanatomy are not well understood.
  • Emesis is the act of forcefully removing gastrointestinal content.
  • Both nausea and emesis are protective mechanisms.
  • Nausea and vomiting can have a variety of causes, conditions, or drugs.

Emesis

  • Emetic reflex is a highly complex system.
  • Chemotherapy-induced nausea and vomiting (CINV), radiation, infections, and pregnancy can cause emesis.
  • Emetic neurotransmitters may include serotonin, dopamine, substance P, prostaglandins, and leukotrienes.

Central & Peripheral Emetic Neurotransmitters & Corresponding Receptors

  • Dorsal Vagus Complex (DVC) in the brainstem contains the area postrema (AP), nucleus tractus solitarius (NTS), dorsal motor nucleus of the vagus (DMNX), and central pattern generator (CPG).
  • Gastrointestinal tract (GIT), enterochromaffin cells, vagal afferents/efferents, splanchnic nerves, and vestibular apparatus in the inner ear have peripheral emetic loci.

Antiemetics Overview

  • No one antiemetic is effective for all types of vomiting.
  • Choices are based on the reason, location and cause.

Antiemetics- Specific Drugs

  • Emetrol: Oral suspension of fructose, glucose, and phosphate used for motion sickness, pregnancy-induced vomiting, or drug-induced vomiting
  • Histamine H₁ Receptor Antagonists: Block emetic vestibular afferent activity from the inner ear, used for motion sickness, and vertigo. (Examples are Dimenhydrinate, Diphenhydramine, Cyclizine & Meclizine)
  • Dopamine D₂ Receptor Antagonists I: Block dopamine D₂ receptors in the CTZ. (Examples are Phenothiazines and butyrophenones)
  • Dopamine D₂ Receptor Antagonists II: Block serotonin 5-HT₃ and dopamine D₂ receptors. (Examples are Metoclopramide, Amisulpride, Olanzapine)
  • Glucocorticoids: Anti-inflammatory agents like dexamethasone used to treat radiotherapy- or chemotherapy-induced nausea and vomiting (CINV), and other conditions.
  • Serotonin 5-HT₃ Receptor Antagonists I: Block 5-HT₃ receptors. (Examples are Ondansetron, Granisetron, Dolasetron & Palonosetron)
  • Serotonin 5-HT₃ Receptor Antagonists II: Attenuates immediate-phase of CINV.
  • Neurokinin NK₁ Receptor Antagonists I & II: Block NK₁ receptors. (Examples are Aprepitant, Netupitant and Rolapitant)
  • Neurokinin NK₁ Receptor Antagonists III: Undergo hepatic metabolism by CYP3A4
  • Neurokinin NK₁ Receptor Antagonists IV: Potential exists for drug-drug interactions

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Description

This quiz focuses on the pharmacology and mechanisms of antiemetics used to treat nausea and vomiting. It covers various antiemetics, their receptor mechanisms, and their clinical applications. Additionally, it addresses the neuroanatomy behind vomiting and the phases of chemotherapy-induced nausea.

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