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Anti-emetics

Anti-emetics

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Anti-emetics

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  1. Anti-emetics • Two centres: Emetic centre (EC) and chemoreceptor trigger zone (CTZ) • Both near the floor of the fourth ventricle, close to the vital centres • EC is within the blood brain barrier (BBB) • CTZ outside in the area postrema • They are connected together

  2. Anti-emetics: Teleology • Rational reflex • prevention of ingestion of noxious substances (sight, smell, taste, texture) • local gut reflexes stimulate vomiting e.g. toxins • backup blood monitoring system, should former two protective reflexes be breached • Irrational reflexes • labyrinth • pregnancy • ‘visual nasties’!

  3. Dopamine Opioids Chemotherapy Anaesthetics Hormones Azotaemia Diabetes CTZ BBB 5 HT3 Acetylcholine Emetic Centre Vestibular Sights Smell Taste Histamine Hypotension Hypoxaemia Gut Vomiting

  4. Anti-emetic agents Chemoreceptor trigger zone • Anti-dopaminergic agents • phenothiazines e.g. chlorpromazine • butyrophenones e.g. droperidol • procainamide derivs. e.g. metoclopramide • benzimidazole derivs. e.g. domperidone

  5. Anti-emetic agents at CTZ Anti-dopaminergic agents … uses • Chemotherapy • Drug induced N and V e.g. opioids and chemotherapy • Parkinson’s disease (domperidone) • Postoperative N and V • Motion sickness ?

  6. Anti-emetic agents at CTZ Anti- 5 HT3 agents • Ondansetron • Granisetron Uses • Chemotherapy (cis-platin) • Postoperative • Expensive !!-

  7. Anti-emetic agents at EC Anticholinergics • Atropine and hyoscine • Glycopyrrolate ? Uses • Travel sickness • Postoperative N and V (combined with opioids)

  8. Anti-emetic agents at EC Anti-histamines • Cyclizine • Promethazine (other actions?) Uses • Postoperative N and V • Sedation (combined with opioids)

  9. Anti-emetic agents: Side effects • Extra-pyramidal effects • Dry mouth and blurred vision • Sedation • Tachycardia • Hypotension

  10. Anti-emetic agents: Choice • Postoperative • Chemotherapy • Travel sickness • Parkinson’s disease (especially apomorphine) • Pregnancy