Antiemetic and Antinausea Drugs 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 o Food intolerance o Motion sickness o Drugs o Surgery o Pregnancy o Poisoning o Cancer therapy Vomiting Center and Chemoreceptor Trigger Zone Vomiting center VC Chemoreceptor trigger zone CTZ o Both located in the brain o Once stimulated cause the vomiting reflex Antiemetics and Antinausea Drugs Anticholinergic drugs Blocking receptor sites Antihistamines histamine 1 H1 receptor blockers Act as a sedative Antidopaminergic drugs Blocking receptor site Prokinetic drugs Only intended to slow motility of GI tract Serotonin blockers Blocking receptor site Tetrahydrocannabinoids Medical marijuana Mechanism of Action o Many different mechanisms of action o Most work by blocking one of the vomiting pathways thus blocking the stimulus that induces vomiting Indications o Specific indications vary per class of antiemetics o General use for each type prevention and reduction of nausea and vomiting Pre medicate Mechanism of Action and Other Indications o 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 Sc p Scopace Used to be used in L D Can cause euphoria Causes drying of the mouth Used for flying boating motion sickness o Antihistamine drugs H1 receptor blockers Inhibit ACh by binding to H1 receptors o o o o o Prevent cholinergic stimulation in vestibular and reticular areas thus preventing nausea and vomiting Also used for motion sickness nonproductive cough allergy symptoms sedation Helps because it is a sedative Examples dimenhydrinate Dramamine Diphenhydramine Benadryl meclizine Antivert o Does not make patient sleepy Antidopaminergic drugs Block dopamine receptors in the CTZ Reduce the likelihood of nausea and vomiting Also used for psychotic disorders intractable hiccups Examples prochlorperazine Compazine and promethazine Phenergan 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 very rare Enhances GI motility Used as a de sensitizer numbs Delays gastric emptying GERD Feeding PEG tubes 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 Created for chemotherapy patients palonosetron Aloxi Cheaper and created for chemotherapy patients 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 Tetrahydrocannabinoids THC cont d dronabinol Marinol Used for nausea and vomiting associated with chemotherapy and anorexia associated with weight loss in AIDS patients Miscellaneous Antinausea Drugs phosphorated carbohydrate solution Emetrol o Mint flavored oral solution o Used off label for treatment of morning sickness o Adverse Effects o Vary according to drug used o Stem from their nonselective blockade of various receptors o Phenergan not given to children because can cause nervous system effects Don t want to use long term Herbal Products Ginger Used for nausea and vomiting including that caused by chemotherapy morning sickness and motion sickness Adverse effects o Anorexia nausea and vomiting skin reactions Drug interactions o May increase absorption of oral medications o Increase bleeding risk with anticoagulants Nursing Implications Assess complete nausea and vomiting history including precipitating factors Assess current medications Assess for contraindications and potential drug interactions 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 o With all of them Teach patients to change positions slowly to avoid hypotensive effects o Except Zofran and Aloxi For chemotherapy antiemetics are often given 30 to 60 minutes before chemotherapy begins Monitor for therapeutic effects Monitor for adverse effects Questions 1 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 A Cataracts B Narrow angle glaucoma C Presbyopia D Detached retina 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 2 A patient is receiving a continuous tube feeding via a PEG tube Which drug would most likely be prescribed for this patient A metoclopramide Reglan B meclizine Antivert C aprepitant Emend D phosphorated carbohydrate solution Emetrol 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 3 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 A prevent recurrence of the chemotherapy induced nausea and vomiting B prevent stress ulcers C improve his mood D stimulate his appetite Rationale Dronabinol is used as an appetite stimulant in patients who are experiencing nutritional wasting due to cancer and cancer treatment 4 A patient is 2 months pregnant She comes to the clinic complaining of severe morning sickness She has tried numerous non pharmacologic