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What is Emesis? What are the drugs used to treat emesis?

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  1. 1. VOMITING(Emesis)
  2. 2. What is the major physiologicalfunction of vomitingto remove non-toxic orharmless substancesfrom the body afteringestion
  5. 5. Can you tell ussome clinicalproblems that mightoccur due to nauseaand vomiting
  6. 6. postoperative nausea andvomiting• Extended hospital stays,• Increased bleeding,• Aspiration pneumonia• Re-opening of surgicalwounds
  7. 7. Reflex mechanism of vomiting• Chemoreceptor Trigger Zone (CTZ)• Vomiting centreThree phases:NAUSEA, RETCHING and VOMITING
  8. 8. Nausea• an unpleasant sensation thatimmediately precedes vomiting. Cold sweat, pallor, salivation. Noticeable disinterest in the surroundings, Loss of gastric tone. Reflux of intestinal contents into the stomachAccompanying symptoms
  9. 9. Retching• follows nauseacompriseslabored spasmodic respiratory movementsagainst a closed glottis with contractions of theabdominal muscles, chest wall and diaphragmwithout anyexpulsion of gastric contents.can occurwithout vomitingbutnormally it generates the pressure gradient thatleads to vomiting.
  10. 10. Vomitingcaused by:• the powerful sustained contraction of theabdominal and chest wall musculature,accompanied by• The descent of the diaphragm and the opening ofthe gastric cardia.It results in the• rapid and forceful evacuation of stomachcontents up to and out of the mouthReflex activity that is not under voluntarycontrol.
  11. 11. Neuronalpathways, transmittersandreceptors involved innausea and vomiting
  12. 12. Mechano and Chemo receptorslocated in• stomach, jejunum and ileuminvolved with• detection of emetic stimuli in thegastrointestinal tract.
  13. 13. Mechanoreceptors aretension receptors that initiate emesisin response todistension and contractione.g. from bowel obstruction.Chemo receptors respond toa variety of toxins in the intestinal lumina
  14. 14. Afferent neuronal pathwaysfrom the abdomen are thesame regardless of thestimulus.
  15. 15. Receptors and neurotransmitters involved in mediating vomiting:Structures Receptors Agonists AntagonistsAreapostremaCTZD2 ApomorphineL-DOPAAntidopaminergic drugsVestibularnucleiN. tractussolitariusM, H1 CholinomimeticsHistamineScopolamineDramamineVomitingcenterM Cholinomimetics(e.g.,physostigmine)ScopolamineVagalsensorynerveendings5-HT3 Serotonin OndansetronGranisetronTropisetron
  16. 16. Vomiting Centrefinal common pathway for efferent responses that produce emesis• controls the act of vomiting.• not a discrete anatomical site, but represents inter-related neuronal networks.• inputs include: vagal sensory pathways from thegastro-intestinal tract and neuronal pathways fromthe labyrinths, higher centres of thecortex, intracranial pressure receptors and thechemoreceptor trigger zone.• When activated induces: vomiting via stimulation ofthe salivary and respiratory centres and thepharyngeal, gastrointestinal and abdominal muscles.
  17. 17. Chemoreceptor Trigger Centre(CTZ)• in the area prostrema of the 4thventricle of the brain• acts as the entry point for emetic stimuli• CTZ is outside the blood-brain barrier• therefore responds to stimuli from eitherthe cerebral spinal fluid (CSF) or theblood.
  18. 18. Mechanism• Impulses from CTZ pass to areaof brainstem called vomitingcentre that control and integratethe visceral and somaticfunctions involved in vomiting.
  19. 19. Main neurotransmitters involved incontrol of vomiting• Acetylcholine• Histamine• 5-HT• Dopamine• Enkephalins• Substance P
  20. 20. Class DrugAnti-cholinergic scopolamine (L-hyoscine)Anti-histamine cinnarizinecyclizinepromethazineDopamine antagonists metoclopramidedomperidonedroperidol (withdrawn 2001)haloperidolCannabinoid nabiloneCorticosteroid dexamethasoneHistamine analogue betahistine5HT3-receptor antagonist granisetronondansetrontropisetron
  21. 21. Causes of Vomiting
  22. 22. Drug/treatment - induced Cancer chemotherapyOpiates, NicotineAntibiotics, RadiotherapyLabyrinth disorders Motion, Menieres diseaseEndocrine causes Pregnancynfectious causes GastroenteritisViral labyrinthitisncreased intracranialpressureHaemorrhage, MeningitisPost-operative Anaesthetics, AnalgesicsProceduralCNS causes AnticipatoryMigraine, Bulimia nervosa
  23. 23. Drugs causing emesis.a. Drugs acting on CTZ.• apomorphine• emetine (when given parenterally and only atlarge doses)• L-DOPA• estrogens (morning sickness of pregnancy)• ergot alkaloids• cardiac glycosides• opiates• cancer chemotherapeutic agents
  24. 24. b. Drugs acting locally on the G-I tract.• Activate enterochromaffin cells• secrete serotonin• acts on the 5-HT3 receptors• at the nerve endings of the vagal sensory fibers.• The afferent fibers transmit excitation to the N.tractus solitarius,• which in turn activates the VC.• These drugs are traditionally called "localirritants".• Ipecac, zinc salts, copper sulfate,
  25. 25. Cancer chemotherapeutic agents andradiation therapy• produce free radicalsenterochromaffin cellsserotonin.• also stimulate CTZ receptors
  26. 26. The management ofNausea &Vomiting
  27. 27. • Identification and elimination of theunderlying cause if possible• Control of the symptoms if it is notpossible to eliminate the underlyingcause• Correction of electrolyte, fluid ornutritional deficiencies
  28. 28. Antiemetics
  29. 29. Class DrugAnti-cholinergic scopolamine (L-hyoscine)Anti-histamine cinnarizinecyclizinepromethazineDopamine antagonists metoclopramidedomperidonedroperidol (withdrawn 2001)haloperidolCannabinoid nabiloneCorticosteroid dexamethasoneHistamine analogue betahistine5HT3-receptor antagonist granisetronondansetrontropisetron
  30. 30. Receptors antagonists•Which receptors H1 - Histamine receptors Muscarinic receptors 5 HT 3 receptors
  31. 31. Antiemetic DrugsH1- receptor antagonist• Cyclizine• Meclizine• Cinnarazine• Promethazin• Diphenhydramine• Dimenhydrinate• HydroxyzineMuscarinic antagonist• Hyoscine (Scopolamine)
  32. 32. D2-receptor antagonistPhenothiazine• Chlorpromazine, prochlorperazine,Promethazine Trifluoperazine.Thiethylperazine.Butyrophenones:• Haloperidol• DroperidolMetoclopramideDomperidone
  33. 33. 5 HT3-receptor antagonistOndansetronGranisetronDolasetronCannabinoids• Nabilone• DronabinolSteroids• Dexamethasone• Methylprednisolone
  34. 34. Clinical Uses of Anti emetics• Histamine H1 receptor antagonistCyclizine Motion sicknessCinnarazine Motion sickness,vestibular disordersPromethazine Morning sickness ofpregnancy
  35. 35. Muscarinic antagonistHyoscine Motion sickness
  36. 36. Dopamine D2 receptor antagonistPhenothiazines vomiting caused byProchlorperazine uremia, radiation,viralgastroenteritis, severemorning sickness ofpregnancy.Metoclopramide uremia,radiation, GI disorders,cytotoxic drugs.
  37. 37. 5-HT3- receptor antagonistDrugs Vomiting caused byOndansetronGranisetronDolasetroncytotoxic anticancer drugs,post operative vomiting,radiation induced vomitingCannabinoids Vomiting caused byanticancer drugs
  38. 38. 5 HT3 AntagonistsOndansetron, Granisetron,Dolasetron, TropisetronPrimary site of action: CTZTherapeutic Use:chemotherapy and radiation inducednausea & vomitingAdverse effects: Rare (headache,GIupsets).
  39. 39. Phenothiazines• Antipsychotics• Commonly used for: nausea and vomitingassociated with vertigo, motion sickness,and migraine.• Act mainly as: antagonist at dopamine D-2receptors in the CTZ• Also block: muscarinic and histaminereceptors• Adverse effects: sedation,hypotension,extra pyramidal symptoms
  40. 40. Metoclopramide and Domperidone• D2 receptor antagonist in CTZ.• Peripheral prokinetic activity:• Domperidone does not cross BBB.Incontrast• Metoclopramide crosses BBBMovement disorder, fatigue, spasmodictorticollis, occulogyric crises, increased prolactinrelease galacorrhea,menstrual irregularitiesIncrease the motility ofesophagus, stomach, and intestine
  41. 41. CannabinoidsDronabinol, Nabilone• Synthetic cannabinol derivative• Mechanism of action: unknownAdverse effects: common:• Drowsiness,dizziness, dry mouth.• Mood changes• Postural hypotension• Hallucinations
  42. 42. CorticosteroidsHigh dose Glucocorticoids• Dexamethasone• Methylprednisolone• Mechanism of action: unclearmay involve inhibitionof PGs