Emetics And Antiemetics Question And Answers

Emetics And Antiemetics

 

Question 1. Mention Classifiation And Uses Of Antiemetics.
Or
Enumerate Antiemetic Agents
Or
Classify Antiemetic Drugs
Answer:

Classification Of Antiemetics

• Anticholinergics: Hyoscine and dicyclomine
• H1 Antihistaminics: Promethazine, cyclizine, meclozine, diphenhydramine, dimenhydrinate, doxylamine, cinnarinzine.
• Neuroleptics: Chlorpromazine, triflupromazine, prochlorperazine, haloperidol, etc.
• Prokinetic drugs: Metoclopramide, domperidone, cisapride, mosapride, itopride
• 5HT3 Antagonists: Ondensetron, granisetron, palonosetron, ramosetron
• NK1 receptor antagonists: Aprepitant, fosaprepitant
• Adjuvant Antiemetics: Benzodiazepines, dexamethasone, dronabinol, and nabilone.

Read And Learn More: Pharmacology Question And Answers

Uses Of Antiemetics

Question 2. Write A Short Note On Metoclopramide.
Answer:

Metoclopramide is a prokinetic drug and antiemetic agent.

Metoclopramide Actions

• Central action: In CNS metoclopramide blocks D2 receptors in CTZ. At larger doses, 5HT3 receptors are blocked. This action produces its antiemetic effect.
• Prokinetic action: Metoclopramide increases acetylcholine release from myenteric neurons. This is due to D2 antagonism and 5HT4 agonism in the gastrointestinal tract. So peripherally it has a prokinetic effect on the upper gastrointestinal tract. It increases gastric and duodenal emptying.

Metoclopramide Pharmacokinetics

• On oral administration, metoclopramide is readily absorbed.
• It can also be given by IV and IM routes.
• After oral administration, its onset of action is under half an hour, and on parenteral administration, its action is after a few minutes.
• It has a half-life of 4 hours which is short.
• It is poorly bound to plasma protein.
• It crosses the blood-brain barrier.
• It is partly metabolized and is excreted in urine.

Metoclopramide Adverse Effects

• Drowsiness, dizziness, diarrhea
• Acute muscle dystonias and other extrapyramidal symptoms
• Chronic use of drugs can cause gynecomastia, galactorrhea, and menstrual irregularities.

Metoclopramide Uses

• Antiemetic: It is a very popular type of drug in vomiting associated with drug-induced, postoperative, disease-associated, migraine-associated, and radiation sickness. It is used in prophylaxis and treatment of vomiting caused due to highly emetic cancer drugs.
• Gastrokinetic: It accelerates gastric emptying when emergency general anesthesia is to be given.
• In dyspepsia and other gastrointestinal disturbances.
• In gastroesophageal reflux disease: Metoclopramide provides sympathetic relief in mild cases.
• It is used in the treatment of intractable hiccups.
• It is used in diabetic gastroparesis.

Metoclopramide Drug Interactions

• Metoclopramide should not be given for levodopa-induced vomiting as it will block D2 receptors in basal ganglia and interfere with the therapeutic actions of levodopa.
• Atropine antagonizes the prokinetic action of metoclopramide.

Question 3. Write A Short Note On Domperidone.
Answer:

Domperidone is an antiemetic drug:

• It has a lower ceiling, antiemetic and prokinetic actions.
• Domperidone crosses the blood-brain barrier poorly. In it extrapyramidal side effects are rare but there are chances of hyperprolactinemia.
• It does not act on CTZ.
• Domperidone is a D2 antagonist and its antiemetic and prokinetic effects are due to the blockade of D2 receptors. It is pharmacologically related to metoclopramide. Its antiemetic efficacy is lower than metoclopramide.
• Domperidone is given orally, its oral bioavailability is low due to its fist-pass metabolism.
• Domperidone counteracts the vomiting caused by levodopa without affecting its antiparkinsonian effect.
• Domperidone is the preferred antiemetic in children.
• Adverse effects of domperidone are xerostomia, diarrhea, headache, skin rashes, galactorrhea, and menstrual irregularities.

Question 4. Compare And Contrast Promethazine And Metoclopramide As Antiemetic.
Answer:

Question 5. Write Drug Treatment Of Vomiting.
Answer:

Drug Treatment Of Vomiting

• Mild to moderate vomiting: Prochlorperazine or metoclopramide orally is given.
• Severe vomiting: Prochlorperazine IM.
• Drug-induced vomiting: Metoclopramide or phenothiazines or ondansetron.
• Postoperative vomiting: Chlorpromazine or ondansetron or metoclopramide or domperidone, promethazine or diphenhydramine
• Vomiting in motion sickness: For motion sickness two kinds of drugs are useful:
  • Anticholinergics: Scopolamine (hyoscine) or atropine and dicyclomine
  • Antihistaminics.
• Vomiting in morning sickness: Pyridoxine, antihistaminic (For Example. meclizine, dimenhydrinate promethazine, doxylamine) or metoclopramide, or a phenothiazine derivative.

Question 6. Write The Therapeutic Uses And Adverse Effects Of Prokinetic Drugs.
Answer:

Question 7. Describe the Management Of Motion Sickness.
Answer:

Management Of Motion Sickness

Motion sickness occurs due to the movement of labyrinthine fluid in the inner ear stimulation of the vestibular apparatus due to which the vomiting reflex is initiated. In this reflex, cholinergic and histaminic receptors are involved. Hence other types of antiemetics are not useful.

Drugs are effective for the prevention of motion sickness only. Once vomiting starts, they are not much effective.

• Hyoscine: 2 mg orally 4-6 hourly or patch x 3 days
• Cyclizine: 25 mg 12 hourly for short journeys and Meclizine 50 mg 24 hourly for longer journeys.

Question 8. Write A Short Note On Antiemetics.
Answer:

Vomiting is a protective mechanism aimed at eliminating unwanted harmful material from the stomach. But in some situations, vomiting may not serve any useful purpose and may only be troublesome. In such circumstances, vomiting needs to be suppressed.

Question 9. Enumerate The Therapeutic Uses Of Metoclopramide.
Answer:

Enumeration Of Therapeutic Uses Of Metoclopramide

• Antiemetic: It is a very popular type of drug in vomiting associated with drug-induced, postoperative, disease-associated, etc. It is used in prophylaxis and treatment of vomiting caused due to highly emetic cancer drugs.
• Gastrokinetic: It accelerates gastric emptying.
• In dyspepsia and other gastrointestinal disturbances.
• In gastroesophageal reflux disease: Metoclopramide provides sympathetic relief in mild cases.
• It is used in the treatment of intractable hiccups.

Question 10. Enumerate The Drugs Used In The Treatment Of Peptic Ulcers. Describe Prokinetic Drugs.
Answer:

Enumeration of drugs used in the treatment of peptic ulcer

•  Reduction of gastric acid secretion
  • H2 antihistaminics: Cimetidine, Ranitidine, famotidine, roxatidine, and loxatidine.
  • Proton pump inhibitor: Omeprazole, lansoprazole, pantoprazole, rabeprazole and Esomeprazole.
  • Anticholinergic agents: Pirenzepine, Propantheline, and oxyphenonium
  • Prostaglandin analogs: Misoprostol
• Neutralization of gastric acid (Antacids)
• • Systemic antacids: Sodium bicarbonate, sodium citrate
  • Nonsystemic antacids: Aluminum hydroxide, magnesium hydroxide, magnesium trisilicate, Magaldrate, Calcium carbonate
• Ulcer protection: Sucralfate, Colloidal Bismuth substrate
• Ulcer healing drugs: Carbenoloxone
• Anti-H. pylori drugs: Amoxicillin, clarithromycin, metronidazole, tinidazole, and tetracycline.

Prokinetic Drugs

Prokinetic drugs are metoclopramide, domperidone, cisapride, mosapride, and itopride.

Prokinetic Drugs Metoclopramide

• Metoclopramide increases acetylcholine release from myenteric neurons. This is due to D2 antagonism and 5HT4 agonism in the gastrointestinal tract. So peripherally it has a prokinetic effect on the upper gastrointestinal tract. It increases gastric and duodenal emptying.
• The prokinetic action of metoclopramide is antagonized by atropine.
• Metoclopramide is used to accelerate gastric emptying when:
  • Emergency general anesthesia has to be given and the patient has taken food less than 4 hours before.
  • To relieve post-vagotomy or diabetic gastroparesis-associated gastric stasis.
  • To facilitate duodenal intubation.

Prokinetic Drugs Domperidone

• Domperidone is a D2 receptor antagonist due to which it acts as a prokinetic drug.
• Prokinetic actions have a lower ceiling in domperidone.
• The prokinetic action of domperidone is not blocked by atropine.
• This drug is preferred in children.

Prokinetic Drugs Cisapride

• It is a prokinetic drug with little antiemetic properties.
• Cisapride leads to gastric emptying, improves lower esophageal sphincter tone, and argues for esophageal peristalsis.
• The prokinetic action of cisapride is exerted mainly through 5-HT4 agonism which promotes acetylcholine release from myenteric neurons, this is aided by 5-HT3 antagonism which suppresses inhibitory transmission in the myenteric plexus.
• Side effects are abdominal cramps and diarrhea.
• The oral bioavailability of cisapride is 33%.
• Cisapride is primarily inactivated by hepatic metabolism by CYP3A4 with t1/2 of 10 hours.
• Indication of cisapride is an adjuvant to proton pump inhibitor in GERD and for impaired gastric emptying.
• Prokinetic Drugs Mosapride
• It produces a prokinetic effect due to its 5HT4 agonism. The drug also produces a weak 5HT3 antagonistic effect.
• It does not lead to extrapyramidal symptoms.
• It is used in dyspepsia, diabetic gastroparesis, and gastroesophageal reflux disease.
• Its side effects are dizziness, diarrhea, and headache. It leads to QT prolongation in ECG.

Prokinetic Drugs Itopride

• Its prokinetic effect is due to D2 antagonism and anticholinesterase activity.
• Its drug interaction is rare and does not lead to extrapyramidal symptoms.

Question 11. Name Six Antiemetic Agents.
Answer:

The following are six antiemetic agents:

• Anticholinergics: Hyoscine
• H1 Antihistaminics: Promethazine
• Neuroleptics: Chlorpromazine
• Prokinetic drugs: Metoclopramide
• 5HT3 Antagonists: Ondansetron
• NK1 receptor antagonists: Aprepitant.