Chapter 52 Antiemetics Flashcards
Drugs used to relieve nausea and vomiting are called antiemetic drugs. Antiemetics help to control vomiting, or emesis, and are also useful in relieving or preventing nausea. Antiemetics are used to prevent?
motion sickness, reduce secretions before surgery, treat delayed gastric emptying, and prevent postoperative nausea and vomiting. Most of these drugs can cause drowsiness.
The serotonin-blocking drugs (ondansetron)
work by blocking?
serotonin receptors located in the GI tract, CTZ, and vomiting center. They are most commonly used for the prevention of chemotherapy-induced nausea and vomiting
Indications
-Specific indications vary per class of antiemetics.
-General use for each type: prevention and reduction of nausea and vomiting
-Mechanism of Action and Other Indications
-Anticholinergic drugs (acetylcholine [ACh] blockers)
Bind to and block ACh receptors in the inner ear labyrinth
Block transmission of nauseating stimuli to CTZ (Chemoreceptor Trigger Zone)
Also block transmission of nauseating stimuli from the reticular formation to the VC (Vomiting Center)
scopolamine (Transderm-Scōp, Scopace)
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)
Antidopaminergic drugs
-Block dopamine receptors in the CTZ
-Also used for psychotic disorders, intractable hiccups
-Examples
promethazine (Phenergan)
droperidol: Use is controversial because of associated cardiac dysrhythmia
Antidopaminergics drug
Promethazine (Phenergan)
- Indications: Psychotic disorders (mania, schizophrenia, anxiety), intractable hiccups, N/V
- MOA: Block dopamine in the CTZ and may also block Ach
Serotonin blockers drug
Ondansetron (Zofran)
- Indications: N/V associated with chemotherapy, postoperative N/V
- MOA: Blocks serotonin receptors in the GI tract, chemoreceptor trigger zone (CTZ), and vomiting center
Anticholinergics (acetylcholine blockers)
Scopolamine (Transderm Scap)
- Indications: Motion sickness, secretion reduction before surgery, N/S
- MOA: Block ACh receptors in the vestibular nuclei and reticular formation
Antihistamine (H1 receptor blockers)
Meclizine (Antivert)
- Indications: Motion sickness, nonproductive cough, sedation, rhinitis, allergy symptoms, N/V
- MOA: Block H1 receptors, thereby preventing ACh from binding to receptors in the vestibular nuclei
Prokinetics
Metoclopramide (Reglan)
- Indications: Delayed gastric emptying, gastroesophageal reflux,N/V
- MOA: Block dopamine in the CTZ or stimulate ACh receptors in the GI tract
Anticholinergics work by blocking?
acetylcholinesterase receptors in the vestibular nuclei and reticular formation, preventing areas in the brain from being activated by nauseous stimuli.
-also tend to dry GI secretions and reduce smooth muscle spasms, effects that are often helpful in reducing acute GI symptoms, including nausea and vomiting.
Antihistamines prevent cholinergic stimulation in both the?
vestibular and reticular systems. Nausea and vomiting occur when these systems are stimulated. Antihistamines work by blocking H1 receptors, which produces the same effect as the anticholinergics.
Antidopaminergic drugs, although traditionally
used for antipsychotic effects, also prevent?
nausea and vomiting by blocking dopamine receptors in the chemoreceptor trigger zone (CTZ). Many also have actions similar to those of anticholinergic drugs. They also calm the central nervous system.
Prokinetic drugs, in particular metoclopramide, act as antiemetics by blocking?
dopamine receptors in the CTZ, which desensitizes the CTZ to impulses it receives from the GI tract.
-The primary action is to stimulate peristalsis in the GI tract. This enhances the emptying of stomach contents into the duodenum, as well as intestinal movements.
The serotonin-blocking drugs (granisetron and ondansetron) work by blocking?
serotonin receptors located in the GI tract, CTZ, and vomiting center. They are most commonly used for the prevention of chemotherapy-induced nausea and vomiting
Prokinetic: Metoclopramide (Reglan)
Long-term use may cause?
Metoclopramide (Reglan)
Long-term use may cause irreversible tardive dyskinesia.
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)
Adverse effects
Vary according to drug used
Stem from their nonselective blockade of various receptors
.
Adverse effects for anticholinergics
Dizziness, drowsiness, disorientation, tachycardia, blurred vision, dilated pupils, dry mouth, difficult urination, constipation, rash, erythema
Adverse effects for antihistamines
Dizziness, drowsiness, confusion, blurred vision, dilated pupils, dry mouth, urinary retention
Adverse effects for prokinetics
Hypotension, supraventricular tachycardia, sedation, fatigue, restelessness, HA, dystonia, dry mouth, N/V, diarrhea
Adverse effects for serotonin blockers
HA, diarrhea, rash, bronchospasm, prolonged QT interval
Interactions with anticholinergics
Additive drying effects when given with antihistamines and antidepressants
Increased CNS depressant effects are seen when antihistamine antiemetics are administered with?
Barbiturates, opioids, hypnotics, triclylic antidepressants, or alcohol
Combining metoclopramide with alcohol can result in?
Additive CNS depression
Anticholinergics and analgesics can block the motility effects of?
Metochlopramide
Anticholinergic: Scopolamine (Transderm-Scop)
- used as antimetic
- potent effects on vestibular nuclei (part of brain that controls balance)
- works by blocking binding of ACh to the cholinergic receptors in this region thereby correcting imbalance between two neurotransmitters ACh and norepinephrine
- Tx of prevention of N/V associated w/motion sickness & postop N/V
- Contraindicated: glaucoma
- oral, injectable, transdermal, ocular forms
- commonly used form for nausea is 72-hour transdermal patch, releases 1 mg of drug
Antihistamine: Meclizine (Antivert)
- Treat dizziness, vertigo, N/V associated with motion sickness
- contraindications: shock and lactation
- oral ONLY
Prokinetic: Metoclopramide (Reglan)
- prescription only
- can cause serious AEs if not used correctly
- Tx of delayed gastric emptying and gastroesophageal reflux and also as an antiemetic
- contraindicated: seizure disorders, pheochromocytoma, breast cancer, GI obstruction, hypersensitivity to it or to procaine or procainamide
- oral and perenteral formulations
- EXTRAPYRAMIDAL AEs can occur with its use, in young adults
- potential for developing TARDIVE DYSKINESIA with longer term use
Serotonin blockers: Ondansetron (Zofran)
- tx chemotherapy-induced nausea and vomiting, postop N/V, tx of hyperemesis gravidarum (N/V associated w/pregnancy)
- contraindication: drug allergy
- oral and injectable forms and as orally disintegrating tablets
- doses up to 8 mg can be given by IV push over 2-5 minutes
- Granisetron available as transdermal patch
- concern regarding cleft palate development in fetus when used in first trimester
Identify any factors precipitating nausea or vomiting; note
any weight loss; measure baseline vital signs; assess intake and output; examine the skin and mucous membranes, noting turgor and color; and assess and document capillary refill
(normal is <5 seconds)
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 pt has a history of this disorder, another antiemetic or antinausea is prescribed
-The same concern applies to antihistamines
Cautions with antihistamines
- narrow angle glaucoma
- pediatric patients who may have severe paradoxical reactions
- older adults may develop agitation, mental confusion, hypotension, and even psychotic-type reactions in response to these drugs
The prokinetic drug (e.g., metoclopramide) is often reserved for the treatment of nausea and vomiting associated with?
antineoplastic drug therapy or radiation therapy and for the treatment of GI motility disturbances
-action of drug is DECREASED when taken with anticholinergics or opiates, assess for this interaction and with alcoho
Contraindications for prokinetic (metoclopramide)
-seizure disorders, GI obstruction, known hypersensitivity, to it or to procain or procainamide
Keep suppository dosage forms in their foil covering until use and, once the wrap is removed, you may?
moisten them with water or water-soluble lubricating gel before being inserted well into the rectum.
Do not give metoclopramide (prokinetic) in combination with any other medications, such as phenothiazines, that would lead to?
exacerbation of extrapyramidal reactions. Report extrapyramidal reactions to the prescriber immediately.
The development of tardive dyskinesia, an involuntary neurologic movement, has been associated with the long-term use of?
metoclopramide
serotonin blocker Ondansetron use requires assessment for the?
S/S of dehydration and electrolyte disturbances
- has warning of its use and the risk for cardiac dysrhythmias
- assess skin turgor, and examine mucous membranes for dryness and/or longitudinal furrows in the tongue
What do you monitor for in patients taking meclizine (antihistamine)?
Frequently monitor BP especially if they are older adults, due to increased sensitivity to the drug’s effects
- be aware of the concern that sedation poses for pt safety, cautious movement at all times
- dry mouth can be alleviated by sugarless gum or hard candy
Metoclopramide (prokinetic) is given?
Orally 30 minutes before meals and at bedtime
- infusing IV dosage forms over the recommended period
- keep solutions for parenteral dosing for only 48 hours, and protect from light
Anticholinergic: Scopolamine transdermal patch is applied?
Behind ear as directed, cleansed and dried before applying patch
- if patch becomes dislodged, the residual drug must be washed off and a fresh patch put in place
- avoid tasks requiring mental clarity or motor skills while taking this
- leave transdermal patch for 72 hours
- commonly applied to prevent postop N/V
Antiemetics are often given _____ minutes before a chemotherapy drug is administered (time may vary depending on the specific drug) and may also be given during the chemotherapeutic treatment.
30 to 60 minutes before a chemotherapy drug is administered
Caution patients taking antiemetic or antinausea drugs
that?
drowsiness and hypotension may occur and to avoid driving and using heavy machinery while taking these medications.
Monitor the patient for adverse effects such as? during antiemetic therapy.
GI upset, drowsiness, lethargy, weakness, extrapyramidal reactions, and orthostatic hypotension
Serotonin Blocker: Ondansetron may be given?
Orally, IM, IV
- Inject IM doses into large muscle mass
- IV push given over 2-5 minutes and infusions over 15 minutes
- oral forms well tolerated
- avoid alcohol and other CNS depressants during therapy and avoid activities requiring mental alertness or motor skills
- if prescribed to prevent postop N/V, dosing is 30 minutes before the end of the surgical procedure
- If given to prevent N/V associated with chemo the drug is given 30-60 minutes prior to Tx
Also used for vertigo and motion sickness. It may precipitate sedation and needs to be used with caution
The antihistamine meclizine (Antivert)
Rotate the transdermal application sites for scopolamine patches. Patches are to be applied to?
Nonirritated areas behind the ear. Wash hands before and after application
Educate patient about the possible AEs of ondansetron, including?
Heart rate irregularities and HA
- HA relieved by taking simple analgesic such as acetaminophen but avoiding aspirin-containing products
- if used during chemo given 30-60 minutes prior to the dosing of the antineoplastic drug
