Antiemetic & Antinausea Drugs PDF

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Antiemetic & Antinausea Drugs...

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Antiemetic & Antinausea Drugs Definitions o Nausea: unpleasant feeling that often precedes vomiting o Emesis (vomiting): forcible emptying of gastric, & occasionally, intestinal contents (obstruction) o Antiemetic drugs: used to relieve nausea & vomiting Vomiting Center & Chemoreceptor Trigger Zone o Vomiting center (VC): area in the brain that is responsible for initiating the physical events that lead to nausea o Chemoreceptor trigger zone (CTZ): neurotransmitter signals are sent to the VC from here o Both located in the brain o Once stimulated, cause the vomiting reflex o Signal alters CTZ & VC & nausea occurs Antiemetics & Antinausea Drugs: Mechanism of Action o Many different mechanisms of action o Most work by blocking 1 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 & reduction of nausea & vomiting Anticholinergic Drugs (ACh Blockers) o Bind to & block acetylcholine (ACh) receptors in the inner ear labyrinth o Block transmission of nauseating stimuli to CTZ o Also block transmission of nauseating stimuli from the reticular formation to the VC o Scopolamine:  Also used for motion sickness (transdermal patch behind the ear)  Most commonly used formulation for nausea is the 72-hour transdermal patch  Releases a total of 1 mg of the drug Antihistamine Drugs (H1 Receptor Blockers) o Inhibit ACh by binding to H1 receptors o Prevent cholinergic stimulation in vestibular & reticular areas, thus preventing nausea & vomiting o Also used for motion sickness, nonproductive cough, allergy symptoms, sedation o Dimenhydrinate (Dramamine); PO o Diphenhydramine (Benadryl): PO/IV 25 mg/ min o Meclizine (Antivert); PO (available OTC) Antidopaminergic Drugs o Block dopamine receptors on the CTZ o Also used for psychotic disorders, intractable hiccups o Prochlorperazine (Comapazine); suppository o Promethazine (Phenergan); dangerous to be given  Preferred route PO/IM/rectal  Extreme caution must be taken to avoid accidental intraarterial injection  Severe tissue damage (necrosis) can occur

Antiemetic & Antinausea Drugs Requiring amputation Dilute in @ least 10 mL (the more dilute the better) some institutions require a 1:1 solution Give in a running IV through a large bore vein (not hand/wrist); antecubital/central line Should NOT be given SQ b/c it causes necrosis Causes burning when given IM Contraindicated in children under 2 

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Prokinetic Drugs o Block dopamine in the CTZ o Cause CTZ to be desensitized to impulses it receives from the GI tract o Stimulate peristalsis in GI tract, enhancing emptying of stomach contents  Used for GERD, delayed gastric emptying o Metoclopramide (Reglan); not an OTC drug b/c of side effects, must be written prescription from HCP who is monitoring the patient  Long-term use may cause irreversible tardive dyskinesia (> 1 year of therapy)  Uncontrolled rhythmic motions of mouth, face, & extremities; lip smacking or puckering, puffing of cheeks, uncontrolled chewing, rapid/worm-like movements of the tongue  Parkinsonian: difficulty speaking/swallowing, loss of balance control, mask like face, shuffling gait rigidity, tremors & dystonic (muscle spasms, twisting motions, inability to move eyes, weakness of arms/legs)  Monitor for neuroleptic malignant syndrome: hyperthermia, muscle rigidity, altered consciousness, irregular pulse/BP, tachycardia, diaphoresis  Administered over 1-2 minutes, if administered quickly it causes intense feeling of anxiety & restlessness followed by drowsiness Serotonin Blockers o Block serotonin receptors in the GI tract, CTZ, & VC o Used for nausea & vomiting in patients receiving chemotherapy & for postoperative nausea & vomiting o Dolasetron (Anzemet) o Granisetron (Kytril) o Ondansetron (Zofran); most common  Prevention of postop nausea & vomiting given 30 minutes before the end of the procedure  4-8 mg IVP before induction or postop  Administer undiluted  Administer preferably over 2-5 minutes (@ least over 30 seconds)  Nausea & vomiting associated w/ chemotherapy IV dose given in the 1st 2448 hours of chemotherapy  0.15 mg/kg IV (or 32 mg single doses)  Dilute doses for in 50 mL D5W/NS  Administer IV infusion over 15 minutes o Palonosetron (Aloxi) Tetrahydrocannabinoids o Major psychoactive substance in marijuana o Inhibitory effects on reticular formation, thalamus, cerebral cortex o Alter mood & body's perception of its surroundings

Antiemetic & Antinausea Drugs o o o

Dronabinol (Marinol) Used for nausea & vomiting associated w/ chemotherapy & anorexia associated w/ weight loss in HIV/AIDS patients Adverse effects:  Vary according to drug used  Stem from their nonselective blockade of various receptors

Herbal Products: Ginger o Used for nausea & vomiting including that caused by chemotherapy, morning sickness, & motion sickness o Adverse effects: anorexia, nausea & vomiting, skin reactions o Drug interactions:  May increase absorption of oral meds  Increase bleeding risk w/ anticoagulants Nursing Implications o Assess complete nausea & vomiting history, including precipitating factors o Assess current meds o Assess for contraindications & potential drug interactions o Many of these drugs cause severe drowsiness; warn patients about driving or performing any hazardous tasks o Taking antiemetics w/ alcohol may cause severe CNS depression o Teach patients to change position slowly to avoid hypotensive effects o For chemotherapy, antiemetics are often given 30-60 minutes before chemotherapy begins  Serotonin blockers: ondansetron (Zofran) o Monitor for therapeutic effects o Monitor for adverse effects...