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Class antiemetics 3


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Class antiemetics 3

  2. 2. Vomiting Centre (medulla) Stomach Small intestine Higher cortical centres Chemoreceptor Trigger Zone (area prostrema, 4th ventricle) Memory, fear, anticipationSensory input (pain, smell, sight) Surgery Surgery Labyrinths Anaesthetics Vomiting Reflex Neuronal pathways Factors which can cause nausea & vomiting Chemotherapy Chemotherapy Radiotherapy Opioids Sites of action of drugs 5HT3 antagonists Sphincter modulators Histamine antagonists Muscarinic antagonists Gastroprokinetic agents Benzodiazepines Histamine antagonists Muscarinic antagonists Dopamine antagonists Cannabinoids
  3. 3. Area Type of receptors Stimulus Chemoreceptor trigger zone (CTZ) a) Dopamine D2 b) 5HT3 c) Opioid d) H1 anti 1) Cancer chemotherapy 2) Opioids 3) Morning sickness Vestibular nuclei a) Muscarinic b) Histamine H1 1) Motion sickness Pharynx and GIT a) 5HT3 1) Cancer chemotherapy 2) Radio therapy 3) Gastroenteritis Cerebral cortex 1) Smell 2) Sight 3) Thought 4) Anticipatory emesis
  4. 4. 1. Anti-dopaminergic agents a) Phenothiazines: Prochlorperazine, Promethazine b) Butyrophenones : Droperidol 2. Anti- 5 HT3 antagonists: Ondansetron,Granisetron 3. Anticholinergics: Atropine, hyoscine , Glycopyrrolate 4. Anti-histamines: Cyclizine, diphenhydramine, Cinnarizine 5. Glucocorticoids: Dexamethazone 6. Cannabinoids: Dronabinol, Nabilone 7. Miscellaneous: Diphenidol, Droperidol, Trimethobenzamide
  5. 5. Substituted benzamides : Metoclopramide Benzimidazole Derivative: Domperidone Anti -5HT4 agonists: cisapride, mosopride, zacopride, renzapride, prucalopride Macrolides: motilin agonists: Erythromycin, Azithromycin, Clarithromycin CCK1 antagonist: loxiglumide
  6. 6.  Phenothiazines are primarily antipsychotic Mechanism of the antiemetic action: inhibition of central dopamine, muscarinic and H1 histamine receptors receptors Use:  Chemotherapy-induced vomiting  Radiotherapy-induced vomiting  postoperative nausea and vomiting
  7. 7.  are primarily antipsychotic agents  Mechanism of the antiemetic action: inhibition of central dopamine receptors  Use:  Chemotherapy-induced vomiting  Radiotherapy-induced vomiting  postoperative nausea and vomiting  Adverse effects: droperidol may prolong the QT inter, therefore, it should not be used in patients with QT prolongation (should only be used in patients who have not responded adequately to alternative agents).
  8. 8. 1. Ondansetron, Granisetron, Dolasetron, Palonosetron 2. Mechanism of action: Peripheral 5-HT3 receptor blockade on intestinal vagal afferents.  Central 5-HT3 receptor blockade in the vomiting center and chemoreceptor trigger zone  High first pass metabolism  Excreted by liver & kidney
  9. 9. 1) Chemotherapy induced nausea and vomiting 2) Post radiation nausea & vomiting 3) Vomiting of pregnancy 4) Postoperative vomiting Adverse drug reactions  Headache and dizziness  Constipation or diarrhoea
  10. 10. Dexamethazone Corticosteroids have antiemetic properties Mechanism of action: possibly by suppressing peritumoral inflammation and prostaglandin production. Use: to enhance efficacy of 5HT3 receptor antagonists in the treatment of chemotherapy-induced vomiting.
  11. 11. Use: prevention or treatment of motion sickness. Adverse effects: sedation, dizziness,confusion, dry mouth, cycloplegia, and urinary retention. . Diphenhydramine dimenhydrinate First generation H1 receptor blockers that have anticholinergic and sedating properties Meclizine First generation H1 receptor blockers that have lesser anticholinergic and sedating properties Hyoscine Muscarinic receptor blocker
  12. 12.  Pharmacokinetics: Readily absorbed after oral administration It undergoes extensive first-pass metabolism with limited systemic bioavailability after single doses. Metabolites are excreted primarily via the biliary-fecal route  Adverse effects: Euphoria or dysphoria, sedation 1. withdrawal syndrome (restless, insomnia and irritability) 2. Autonomic effects (sympathetic) in the form of tachycardia, palpitation, orthostatic hypotension.  Use: For the prevention of chemotherapy-induced nausea and vomiting
  13. 13.  Substituted benzamides Metoclopramide  5HT3 and 5HT4 receptor antagonist  Mechanism of antiemetic action: Central dopamine- receptor blockade  Prokinetic effects- activation of 5HT4 receptors  Side effects: (mainly extrapyramidal):  Restlessness,Dystonias  Parkinsonian symptoms  Galactorrhoea and gynacomastia
  14. 14.  Structurally similar to haloperidol  MOA similar to metaclopramide  Used to prevent emetic side effect of levodopa or bromocriptine
  15. 15.  Ipecac is an OTC drug  Administration  Take with a glass of water or fluid, not with milk or carbonated beverage  Vomiting occurs in 20 to 30 minutes and if not, repeat dose  Gastric lavage may be needed if vomiting does not occur  Caution: avoid vomiting if substance is caustic or petroleum  Apomorphine is a morphine derive emetic, SQ/IM, Onset 15 min
  16. 16.  Cisapride, Mosopride, Zacopride, Renzapride, Prucalopride  -no antiemetic effect  Promote release of Ach from myentric plexus  Cisapride- facilitates gastric motility, throughout the GIT  Hastens gastric emptying, improves LES tone  And oesophageal peristalsis.
  17. 17.  Abdominal cramps, diarrhoea  QT prolongation  Cytochrome P450 inhibition 
  18. 18.  Motilin receptors  Increase LES tone  CCK1 receptor antagonist  Loxiglumide –increase GI motility