Antiemetic and Antinausea Drugs Chapter 52 Antiemetic and Antinausea Drugs Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Definitions Nausea Unpleasant feeling that often precedes vomiting Emesis (vomiting) Forcible emptying of gastric, and occasionally, intestinal contents Antiemetic drugs Used to relieve nausea and vomiting Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Vomiting Center and Chemoreceptor Trigger Zone Vomiting center (VC) Chemoreceptor trigger zone (CTZ) Both located in the brain Once stimulated, cause the vomiting reflex Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Antiemetics and Antinausea Drugs Anticholinergic drugs Antihistamines (histamine 1 [H1] receptor blockers) Antidopaminergic drugs Prokinetic drugs Serotonin blockers Tetrahydrocannabinoids Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Antiemetics and Antinausea Drugs: Mechanism of Action Many different mechanisms of action Most work by blocking one of the vomiting pathways, thus blocking the stimulus that induces vomiting Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Indications Specific indications vary per class of antiemetics General use for each type: prevention and reduction of nausea and vomiting Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Mechanism of Action and Other Indications Anticholinergic drugs (ACh blockers) Bind to and block acetylcholine (ACh) receptors in the inner ear labyrinth Block transmission of nauseating stimuli to CTZ Also block transmission of nauseating stimuli from the reticular formation to the VC scopolamine (Transderm-Scōp, Scopace)   Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question The nurse is preparing to administer scopolamine to a patient. It is most important for the nurse to determine if the patient has a history of which condition? Cataracts Narrow-angle glaucoma Presbyopia Detached retina Correct answer: B Rationale: The nurse should only administer the anticholinergic drug scopolamine after careful assessment of the patient’s health history and medication history. One very important concern to reemphasize with scopolamine, which is commonly administered in patch form to prevent motion sickness, is the contraindication to its use in patients with narrow-angle glaucoma. If the patient has a history of this disorder, then another antiemetic or antinausea drug should be used. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Mechanism of Action and Other Indications (cont’d) Antihistamine drugs (H1 receptor blockers) Inhibit ACh by binding to H1 receptors Prevent cholinergic stimulation in vestibular and reticular areas, thus preventing nausea and vomiting Also used for motion sickness, nonproductive cough, allergy symptoms, sedation Examples dimenhydrinate (Dramamine) diphenhydramine (Benadryl) meclizine (Antivert) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Mechanism of Action and Other Indications (cont’d) Antidopaminergic drugs Block dopamine receptors in the CTZ Also used for psychotic disorders, intractable hiccups Examples prochlorperazine (Compazine) promethazine (Phenergan) droperidol: Use is controversial because of associated cardiac dysrhythmia Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Mechanism of Action and Other Indications (cont’d) Prokinetic drugs Block dopamine receptors in the CTZ Cause CTZ to be desensitized to impulses it receives from the GI tract Also stimulate peristalsis in GI tract, enhancing emptying of stomach contents Also used for gastroesophageal reflux disease (GERD), delayed gastric emptying metoclopramide (Reglan) Long-term use may cause irreversible tardive dyskinesia Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question A patient is receiving a continuous tube feeding via a PEG tube. Which drug would most likely be prescribed for this patient? metoclopramide (Reglan) meclizine (Antivert) aprepitant (Emend) phosphorated carbohydrate solution (Emetrol) Correct answer: A Rationale: Metoclopramide is a prokinetic drug that promotes the movement of substances through the gastrointestinal tract and increases gastrointestinal motility. This action is helpful in preventing aspiration in those receiving tube feedings. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Mechanism of Action and Other Indications (cont’d) Serotonin blockers Block serotonin receptors in the GI tract, CTZ, and VC Used for nausea and vomiting in patients receiving chemotherapy and for postoperative nausea and vomiting Examples dolasetron (Anzemet) granisetron (Kytril) ondansetron (Zofran) palonosetron (Aloxi) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Mechanism of Action and Other Indications (cont’d) Tetrahydrocannabinoids Major psychoactive substance in marijuana Inhibitory effects on reticular formation, thalamus, cerebral cortex Alter mood and body’s perception of its surroundings, which may help relieve nausea and vomiting Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question A patient with terminal cancer has not had chemotherapy for a few weeks and has had no nausea or vomiting since then. However, he is taking dronabinol twice a day. The reason for the dronabinol order is to prevent recurrence of the chemotherapy-induced nausea and vomiting. prevent stress ulcers. improve his mood. stimulate his appetite. Correct answer: D Rationale: Dronabinol is used as an appetite stimulant in patients who are experiencing nutritional wasting due to cancer and cancer treatment. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Mechanism of Action and Other Indications (cont’d) Tetrahydrocannabinoids (THC) (cont’d) dronabinol (Marinol) Used for nausea and vomiting associated with chemotherapy, and anorexia associated with weight loss in AIDS patients Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question A patient is 2 months pregnant. She comes to the clinic complaining of severe morning sickness. She has tried numerous non-pharmacologic measures to relieve the morning sickness, but they have not worked. The nurse anticipates the use of which antinausea drug? phosphorated carbohydrate solution (Emetrol) aprepitant (Emend) palonosetron (Aloxi) dolasetron (Anzemet) Correct answer: A Rationale: Phosphorated carbohydrate solution (Emetrol) is a mint-flavored, pleasant-tasting oral solution used to relieve nausea. It works by direct local action on the walls of the GI tract, where it reduces cramping caused by excessive smooth muscle contraction. It can be used to control mild cases of nausea and vomiting. It does not have a pregnancy category rating, but one of its listed unlabeled (non–FDA-approved) uses is for treatment of morning sickness during pregnancy. The other drugs are not indicated for use in pregnancy. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Miscellaneous Antinausea Drugs phosphorated carbohydrate solution (Emetrol) Mint-flavored oral solution Used off label for treatment of morning sickness aprepitant (Emend) Used for the prevention of nausea and vomiting associated with highly emetogenic cancer chemotherapy regimens Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Adverse Effects Vary according to drug used Stem from their nonselective blockade of various receptors Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question Which group of drugs used to treat nausea does the nurse identify as most likely to cause a prolonged QTc interval? Prokinetics Antidopaminergics Tetrahydrocannabinoids Serotonin blockers Correct answer: D Rationale: The serotonin blockers have the potential to cause prolonged QTc interval. Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Herbal Products: Ginger Used for nausea and vomiting, including that caused by chemotherapy, morning sickness, and motion sickness Adverse effects Anorexia, nausea and vomiting, skin reactions Drug interactions May increase absorption of oral medications Increase bleeding risk with anticoagulants Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question A patient tells the nurse that he takes ginger almost every day for nausea. It is most important for the nurse to determine if the patient is taking which medication? furosemide (Lasix) acetaminophen (Tylenol) warfarin (Coumadin) calcium supplements Correct answer: C Rationale: Use of ginger can increase absorption of all oral medications and may theoretically increase bleeding risk with anticoagulants (e.g., warfarin [Coumadin]) or antiplatelet drugs (e.g., clopidogrel [Plavix]). Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. Nursing Implications Assess complete nausea and vomiting history, including precipitating factors Assess current medications Assess for contraindications and potential drug interactions Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Nursing Implications (cont’d) Many of these drugs cause severe drowsiness; warn patients about driving or performing any hazardous tasks Taking antiemetics with alcohol may cause severe CNS depression Teach patients to change positions slowly to avoid hypotensive effects Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Nursing Implications (cont’d) For chemotherapy, antiemetics are often given 30 to 60 minutes before chemotherapy begins Monitor for therapeutic effects Monitor for adverse effects Copyright © 2014 by Mosby, an imprint of Elsevier Inc.