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Chapter 59 Emetic and Antiemetic Agents

Chapter 59 Emetic and Antiemetic Agents. Managing Nausea and Vomiting. Emetics Cause vomiting No longer recommended for at-home poison control Antiemetic Decrease or prevent nausea and vomiting Centrally acting or locally acting Varying degrees of effectiveness.

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Chapter 59 Emetic and Antiemetic Agents

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  1. Chapter 59Emetic and Antiemetic Agents

  2. Managing Nausea and Vomiting • Emetics • Cause vomiting • No longer recommended for at-home poison control • Antiemetic • Decrease or prevent nausea and vomiting • Centrally acting or locally acting • Varying degrees of effectiveness

  3. Sites of Action of Emetics/Antiemetics

  4. Groups of Centrally Acting Antiemetics • Phenothiazines (prochlorperazine) • Nonphenothiazines ( Metoclopramide, steroids ie. Dexamethasone) • Serotonin (5-HT3) receptor blockers (ondasetron) • Substance P/neurokinin 1 receptor antagonists • Anticholinergics (scopolamine) • Miscellaneous group

  5. Focus on the Antiemetic Prototype: Prochlorperazine (Compazine) • Indications:Control of severe nausea and vomiting due to causes such as migraine and vertigo • Adverse effects: constipation,dry mouth,sleepiness, dizziness, blurred vision. • Actions:Mechanism of action not understood; depresses various areas of the CNS • Routes: Oral, PR, IM, IV • Unknown; metabolized in the liver and excreted in urine

  6. Focus on the Nonphenothiazine Antiemetic Prototype: Metoclopramide (Reglan) • Indications:Prevention of nausea and vomiting associated with emetogenic cancer chemotherapy; prevention of postoperative nausea and vomiting, opiod medications • Actions: Blocks dopamine receptors and accelerated gastric emptying, reduces refluxenhances motility og the upper GI tract • Routes: Oral, IM, IV • 5–6 hr; metabolized in the liver and excreted in urine

  7. Metoclopramide • Pharmokinetics: Peak plasma conc occur 30-180 mins after oral administration, 10-15 mins after IM dose and within 5-20 mins after IV • Half life 2.5-5 hours • CNS depressant effect with a combination of metoclopramide and CNS depressant drug. • Adverse effects: diarrhoea, sleepiness, restlessness, dizziness, headache, hypotension, taccycardia • Caution: In parkinsons disease and depression can worsen symptoms • Dosage: Oral 10mg QID

  8. Anticholinergics/Muscarinic Receptor Antagonists • Types • Hyoscine (scopolamine) • Action • Action of acetylcholine at muscarinic receptors and is used to prevent motion induces nausea and vomiting by depressing conduction in the labyrinth of the inner ear • Adverse effects: Dry mouth, taccy, blurred vision, const, mental conf, fatigue and restlessness • Admin: 30 mins prior to travel eg. Travacalm

  9. 5-HT3 Receptor Blockers • Action • Block those receptors associated with nausea and vomiting in the CTZ (chemoreceptor trigger zone) and locally • Types • Dolasetron (Anzemet), tropisetron, ondansetron (Zofran), and palonosetron (Aloxi) • Pharmacokinetics • Rapidly absorbed, metabolized in the liver, and excreted in urine and feces

  10. Focus on the 5-HT3 Receptor Blockers Prototype: Ondansetron • Indications:Control of severe nausea and vomiting associated with emetogenic cancer chemotherapy, radiation therapy; treatment of postoperative nausea and vomiting • Actions:Blocks specific receptor sites associated with nausea and vomiting, peripherally and in the CTZ • Oral route: Onset 30–60 min; duration 1.7–2.2 h • IV route: Onset immediate; duration infusion time • :3.5–6 h; metabolized in liver; excreted in urine

  11. 5- HT 3 Receptor Antagonist/ Ondansetron • Ondansetron first used in nausea and vomiting asscoc with cytotoxic agents and radiotherapy • Pharmakinetics: Max 1-1.5 hrs and plasma half life is 3-4 hours. Met in liver Less than 10% excreted unchanges in urine • Adverse effects: constipation, headache, anxiety and dizziness • Caution: In patients with liver damage • Dosage: Oral 8mg thirty mins before chemo then 4-8mg every 12 hours for 1-2 days

  12. Indications for Antiemetics • Phenothiazines • Nausea and vomiting, including that associated with anesthesia; severe vomiting; intractable hiccoughs • Anticholinergics • Nausea and vomiting associated with motion sickness or vestibular (inner ear) problems • 5-HT3 receptor blockers/substance P/neurokinin 1 receptor antagonists • Nausea and vomiting with emetogenic chemotherapy

  13. Contraindications to Use of Substance P/ Neurokinin 1 Receptor Antagonists • History of allergy to antiemetic • Impaired renal or hepatic function • Pregnancy or lactation • Coma or semiconscious state • CNS depression • Hypotension or hypertension • Active peptic ulcer • CNS injury

  14. Sample Nursing Diagnoses for the Patient Receiving an Antiemetic • Acute Pain related to CNS, skin, and GI effects • Risk for Injury related to CNS effects • Decreased Cardiac Output related to cardiac effects • Deficient Knowledge regarding drug therapy

  15. Implementation for the Patient Receiving Antiemetics • Assess patient carefully for potential drug–drug interactions • Provide comfort and safety measures • Provide support and encouragement • Provide thorough patient teaching

  16. Topics of Patient Teaching for the Patient Receiving Antiemetics • Name of drug • Dosage prescribed • Proper administration • Measures to avoid adverse effects • Warning signs of problems • The importance of periodic monitoring and evaluation • The need to avoid overdose and poisoning

  17. Antacids • Chemical compounds that neutralise hydrochloric acid in the stomach and thereby increase gastric PH • Ingredient: aluminium hydroxide, calcium carbonate, magnesium salts and sodium bicarbonate • Dexsal, Gastrogel, Gaviscon, Mylanta, Quick Eze • Dosage: Varies to individual. Fasting effects lasts 20-40 mins. 1 hour after meal effects up to 3 hours. • Liquid and powder from more effective

  18. Ulcer healing drugs • Acid secretion reducers • Histamine H2 receptor antagonists • Cimetidine and ranitidine block the action of histamine on the parietal cells and reduce acid secretion • Relieve pain and usually heal ulcers in 4-6 weeks. • Common adverse reactions include diarrhoea, constipation, headache, dizziness, rash and confusion.

  19. Sucralfate • Composed of sulphated sucrose and aluminium hydroxide. • In presence of acid undergoes chemical reaction that results in sticky yellow white gel that forms a protective acid resistant shield • This barrier hastens healing of peptic ulcers by protecting the mucosa for up to six hours • Short term use up to 8 weeks

  20. Misoprostil • Indicated for treatment of peptic ulcers and prevention of gastric ulcers assoc with the use of NSAIDS. • Misoprostil suppresses gastric acid secretion and thus helps to heal gastric ulcers • Can cause hypotension in patients with cerebrovascular and coronary artery disease • Misoprostil can induce premature labour and may be tetrogenic in large doses

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