Drug Therapy For Nausea

Aprepitant (Emend): Action

: blocking activity of substance P at NK1 receptors in brain, inhibiting signal to the brain that causes nausea. Has little or no effect on serotonin, dopamine, or corticosteroid receptors.

Promethazine (Phenergan): Administering the Medication

A BLACK BOX WARNING alerts nurses that promethazine is contraindicated for subcutaneous administration. The preferred route of administration is intramuscular, which reduces risk of surrounding muscle and tissue damage. However, the drug can cause pain at the injection site. The nurse avoid intravenous (IV) administration, if possible, because the drug can cause severe tissue injury.

Nausea and vomiting have diverse causes. Which of the following are causes for nausea and/or vomiting? Select all that apply. A. Metabolic disorders B. Progesterone preparations C. Neurologic disorders D. Hypertension E. Urticaria (NCLEX THE POINT)

ANSWER: A & C → Causes of nausea and vomiting include neurologic disorders and metabolic disorders.

The nurse would question an order for which of the following antiemetics for treatment of motion sickness-induced nausea? A. prochlorperazine (Compazine) B. dimenhydrinate (Dramamine) C. meclizine (Antivert) D. scopolamine (Transderm Scop) (NCLEX SUCCESS)

ANSWER: A → Anticholinergics such as scopolamine and antihistamines such as dimenhydrinate and meclizine are the drugs of choice for motion sickness-induced nausea. Phenothiazines such as prochlorperazine are usually effective in pre- venting or treating nausea and vomiting induced by drugs, radiation therapy, surgery, and most other stimuli, but they are usually ineffective in motion sickness.

The nurse knows that antiemetics are most effective when administered A. Before an emetogenic event occurs B. During an episode of nausea but before vomiting has occurred C. After the patient has experienced nausea and vomiting D. Timing of administration has no impact on drug effectiveness (NCLEX SUCCESS)

ANSWER: A → Antiemetic drugs are used to prevent or treat nausea and vomiting, but they are more effective in prophylaxis than treatment.

Ingesting prescribed medication can result in allergic reactions and adverse effects. What are the most common adverse effects of drug therapy? A. Nausea and vomiting B. Elevated temperature and vomiting C. Nausea and elevated temperature D. Respiratory depression and rash (NCLEX THE POINT)

ANSWER: A → Nausea and vomiting are the most common adverse effects of drug therapy.

Medications are given postoperatively to prevent or treat severe nausea and vomiting associated with the surgery. What serotonin receptor antagonist would you expect the surgeon to order? A. Ondansetron B. Levodopa C. Metclopramide D. Promethazine (NCLEX THE POINT)

ANSWER: A → Ondansetron, granisetron, dolasetron, and palonestron are used to prevent or treat moderate to severe nausea and vomiting associated with cancer chemotherapy, radiation therapy, and postoperative status. Ondansetron is commonly used postoperative antiemetic.

Different medications are used to treat the differing causes of nausea and vomiting. Scopolamine, an anticholinergic drug, is particularly effective in which of the following circumstances? A. Motion sickness B. Chemotherapy C. Idiopathic nausea D. Anticipatory nausea (NCLEX THE POINT)

ANSWER: A → Scopolamine, an anticholinergic drug, is effective in relieving nausea and vomiting associated with motion sickness and radiation therapy.

When administering 5-HT3 receptor antagonists before cancer chemotherapy, the nurse should also be prepared to administer which of the following adjunc-tive medications? A. Promethazine B. Dexamethasone C. Dronabinol D. Hydroxyzine (NCLEX SUCCESS)

ANSWER: B→ Clinical studies show corticosteroids such as dexamethasone increase the effectiveness of 5-HT3 receptor antagonists in controlling chemotherapy-induced nausea and vomiting. They are commonly used in the manage- ment of chemotherapy-induced emesis and postoperative nausea and vomiting.

When teaching a group of recent nursing graduates about the clinical use of promethazine, a nursing educator should emphasize the fact that this drug is absolutely contraindicated with which of the following patient populations? A. Pregnant women B. Patients with type 1 diabetes C. Children under the age of two D. Adults who are taking tricyclic antidepressants (NCLEX THE POINT)

ANSWER: C → A black box warning alerts nurses that promethazine is contraindicated in children younger than 2 years of age because of the risk of potentially fatal respiratory depression. The drug is not absolutely contraindicated in pregnancy (category c) or with patients who have diabetes are taking tricyclic antidepressants

Different medicatons are used to treat the differing cause of nausea and vomiting. Antihistamines may be effective in the treatment of nausea and vomiting that is attributable to A. Radiation therapy B. Surgery C. Motion sickness D. Drugs (NCLEX THE POINT)

ANSWER: C → Antihistamines are usually effective in preventing or treating nausea and vomiting induced by motion sickness. Not all histamines are effectives as antiemetic agents.

A patient has purchased OTC dimenhydrinate (Dramamine) to treat nausea. The nurse should convey which of the following teaching points to this patient? A. The drug has a high potential for abuse B. The drug protects against nausea for up to 3 days C. The drug takes up to 4 hours to achieve full effect D. The drug can cause significant anticholinergic effects (NCLEX THE POINT)

ANSWER: C → Dimenhydrinate typically takes a minimum of 4 hours to take a full effect. It does not have a high potential for abuse and does not protect against nausea for consecutive days. Dimenhydrinate does not cause anticholinergic effects.

The nurse is providing care for an adult patient whose nausea is being treated with promethazine. The nurse should consequently assess for what adverse effect? A. Pruritus B. Peripheral edema C. Urinary retention D. Nausea (NCLEX THE POINT)

ANSWER: C → The nurse assesses the patient who is taking promethazine for associated adverse anticholinergic effects, including dry mouth, blurred vision, urinary retention, constipation, acute confusion, dizziness, tachycardia. Pruritus and edema are not typical. Nausea is an indication for use, not an adverse effect.

A patient with recurrent nausea has been prescribed promethazine. The nurse should anticipate what route of administration? A. Topical B. Intravenous C. Intramuscular injection D. Subcutaneous injection (NCLEX THE POINT)

ANSWER: C → The preferred route of promethazine administration is intramuscular, which reduces risk of surrounding muscle and tissue damage.

A female patient with a complex medical history has been experiencing frequent nausea and has vomited several times over the past 24 hours. When considering the use of aprepitant, what variable must be accounted for? A. The potential for dependence B. The fact that the drug is pregnancy category x C. The fact that the drug is still pending FDA approval D. The potential for drug interactions (NCLEX THE POINT)

ANSWER: D → Aprepitant produces significant interactions that alter the effectiveness of other medications. It is approved for use and is pregnancy category B. It does not have a high potential for dependence.

A patient who is undergoing cancer treatment is being discharged home with a prescription for ondansetron (Zofran). When providing health education, the nurse should describe actions that the patient can take to address what common adverse effect? A. Dry cough B. Shortness of breath C. Anorexia D. Diarrhea (NCLEX THE POINT)

ANSWER: D → Diarrhea is a common adverse effect of Zofran; therefore, the nurse also needs to assist patients and caregivers with appropriate use of the drugs and other interventions to prevent fluid and electrolyte depletion.

An older adult patient with early stage Alzheimer's disease has had hydroxyzine prescribed for nausea. When planning the patient's care, the nurse should consequently identify what risk nursing diagnosis? A. Risk for impaired skin Integrity related to adverse effects of hydroxyzine B. Risk for functional urinary incontinence related to adverse effects of hydroxyzine C. Risk for infection related to adverse effects of hydroxyzine D. Risk for falls related to adverse effects of hydroxyzine (NCLEX THE POINT)

ANSWER: D → Hydroxyzine creates drowsiness, which may place a patient at risk for experiencing a fall. This is especially true in the case of an underlying cognitive disorder.

Some medications are more likely to cause the adverse effects of nausea and vomiting that others. With which medications are nausea and vomiting especially associated? A. Beta-adrenergic blockers B. Selective serotonin reuptake inhibitors (SSRIs) C. Loop diuretics D. Opioid analgesics (NCLEX THE POINT)

ANSWER: D → Nausea and vomiting are especially associated with alcohol, aspirin, digoxin, anticancer drugs, antimicrobials, estrogen preparations, and opioid analgesics.

Odansetron (Zofran) has been prescribed for a patient who is experiencing significant postoperative nausea. The nurse who is administering this drug should be aware that it achieves a therapeutic effect by which of the following means? A. Blocking the action of acetylcholine in the brain B. Blocking dopamine from receptor sites in the brain C. Blocking the activity of substance P at NK1 receptors D. Antagonizing serotonin receptors (NCLEX THE POINT)

ANSWER: D → Ondansetron and the other 5-HT3 receptor antagonists antagonize serotonin receptors, preventing their activation by the effects of emetogenic drugs and toxins. These drugs do not block substance P, dopamine, or acetylcholine.

A woman sends her partner to the store to purchase an over-the-counter product to resolve the vomiting she has experienced during a migraine. She has a history of diabetes mellitus and hypertension. She has an appointment with her health care provider in the morning. Which of the following drugs would be the best for the partner to purchase? A. promethazine (Phenergan) B. phosphorated carbohydrate solution (Emetrol) C. meclizine (Antivert) D. dimenhydrinate (Dramamine) (NCLEX SUCCESS)

ANSWER: D → People with chronic health conditions, particularly diabetes, should seek medical assistance with symptoms of vom- iting. Few over-the-counter medications should be taken without input from the health care provider. Only dimenhydrinate and phosphorated carbohydrate solution are avail- able over the counter. Phosphorated carbohydrate solution contains fructose, and patients with diabetes mellitus should be aware that serum glucose levels may increase with its use.

The anatomical structures involved the physiologic process of vomiting are activated by various stimuli. Which is the consummating step in the physiologic process of vomiting? A. Diaphragm contraction B. 5-HT3 receptor activation C. CTZ activation D. Reverse peristalsis (NCLEX THE POINT)

ANSWER: D → When stimulated, the vomiting center initiates efferent impulses that stimulate the salivary center, cause closure of the glottis; contraction of abdominal muscles and the diaphragm; relaxation of the gastroesophageal sphincter, and reverse peristalsis, which moves stomach contents towards the mouth for ejection.

Ondansetron (Zofran): Assessing for Adverse Effects

Because headache & diarrhea are most common adverse effects, give special attention when assessing for these effects. Evaluate for stamina and balance. Note use of ondansetron may mask a progressive ileus & gastric distension following abdominal surgery or in patients w/ chemotherapy-induced N/V.

A child is hospitalized because of persistent vomiting. The nurse monitors the child closely for: A. Diarrhea B. Metabolic acidosis C. Metabolic alkalosis D. Hyperactive bowel sounds (NCLEX SAUNDERS)

C. Metabolic alkalosis

Promethazine (Phenergan): Contraindications

Cautious use necessary w/ glaucoma because the drug possesses antimuscarinic activity.

The client has a PRN prescription for ondansetron (Zofran). For which condition should the nurse administer this medication to the postoperative client? A. Paralytic ileus B. Incisional pain C. Urinary retention D. Nausea and vomiting (NCLEX SUCCESS)

D. Nausea and vomiting

The client has a prescription for metoclopramide (Reglan). On review of the chart, the nurse identifies that this medication can be safely administered with which condition? A. Intestinal medication B. Peptic ulcer with melena C. Diverticulitis with perforation D. Vomiting following cancer chemotherapy (NCLEX SUCCESS)

D. Vomiting following cancer chemotherapy

Hydroxyzine (Vistaril, Atarax): Other Drugs in class

Dimenhydrinate (Dramamine) & meclizine (Antivert, Bonine) used to prevent N/V, dizziness, & vertigo associated w/ motion sickness. (available OTC)

Patient Teaching Guidelines: Antiemetic Drugs General Considerations

General Considerations • Try to identify the circumstances that cause or aggravate nausea and vomiting and avoid them when possible. • Drugs are more effective in preventing N/V than stopping them; should be taken before causative event when possible. • Do not eat, drink, or take oral medications during acute vomiting episodes, to avoid aggravating the stomach upset. • Lying down may help nausea and vomiting to subside; activity tends to increase stomach upset. • After your stomach has settled down, try to take enough fluids to prevent dehydration & serious problems. Tea, broth, and gelatins are usually tolerated. • Do not drive an automobile or operate dangerous machinery if drowsy from antiemetic drugs, to avoid injury. • Do not drink alcohol or take other drugs w/out consulting HCP. Many drugs interact w/ antiemetics, to increase adverse effects. • Dronabinol, derived from marijuana & recommended only for N/V associated w/ cancer chemotherapy, can cause dizziness, drowsiness, mood changes, & other mind-altering effects. Avoid alcohol & other drugs that cause drowsiness. Do not drive or perform hazardous tasks requiring alertness, coordination, or physical dexterity, to decrease risks of injury.

Ondansetron (Zofran): Other Drugs in Class

Granisetron & dolasetron may be given IV or orally. Safety & efficacy have not been established for children younger than 2 years. Palonosetron is given only IV. Safety & efficacy has not been confirmed in patients younger than 18 years of age.

Ondansetron (Zofran): Administering the medication

Important not to remove the tablet from the blister pack until administration. Gentle removal is essential; it is necessary to peel back the blister backing and not push the tablet through the foil.

Nausea and Vomiting: Clinical Manifestations

Nausea—unpleasant abdominal sensation that is often, but not always, accompanied by vomiting. Emesis is the stomach contents produced with vomiting.

Hydroxyzine (Vistaril, Atarax): Administering the Medication

Oral administration is often unsuccessful w/ N/V. Important to give medication IM deep into large muscle, not subcutaneously. IV administration can result in a sterile abscess w/ damage to tissue. o Assessing for Therapeutic Effects: assesses for the absence of nausea and vomiting.

Substance P/Neurokinin 1 Antagonist: Aprepitant

Substance P/Neurokinin 1 Antagonist: Aprepitant • Peptide neurotransmitter in the neurokinin family. Plays a role in mediating acute chemotherapy-induced N/V (along w/ serotonin) & believed to be primary mediator of delayed N/V associated w/ chemotherapy. • Aprepitant (Emend) is the prototype of the class.

5-Hydroxytryptamine3 (5-HT3) or Serotonin Receptor Antagonists

Usually considered first choice for postop N/V. Ondansetron (Zofran) is the prototype of the 5-HT3 receptor antagonists.

Promethazine (Phenergan): Action

ability to block dopamine from receptor sites in the brain and CTZ.

Hydroxyzine (Vistaril, Atarax): Adverse Effects

adverse anticholinergic effects—drowsiness, dizziness, confusion, dry mouth, thickened respiratory secretions, blurred vision, urinary retention, & tachycardia. Contraindications include known sensitivity to the drug.

Ondansetron (Zofran): Action

antagonize serotonin receptors, preventing their activation by the effects of emetogenic drugs & toxins.

Aprepitant (Emend): Assessing for Therapeutic Effects

assess for absence of N/V after chemotherapy or during the postoperative period.

Promethazine (Phenergan): Assessing for Adverse Effects

assess for associated adverse anticholinergic effects (dry mouth, blurred vision, urinary retention, constipation, acute confusion, dizziness, tachycardia). Necessary to be aware that hallucinations, convulsions, & sudden death may occur w/ excessive doses. Also assess tissue integrity w/ injection of the drug because the drug may cause severe tissue injury; burning & pain at IV site immediate discontinuation of the drug.

Hydroxyzine (Vistaril, Atarax): Assessing for Adverse Effects

assess for presence of anticholinergic effects (blurred vision, urinary retention, constipation, thick secretions, & blurred vision.) Patients w/ narrow-angle glaucoma, prostatic hyperplasia, & asthma are at greater risk for adverse effects.

Ondansetron (Zofran): Assessing for Therapeutic Effects

assess for verbal reports of decreased nausea and the absence of vomiting.

Hydroxyzine (Vistaril, Atarax): Assessing for Therapeutic Effects

assesses for the absence of nausea and vomiting.

Promethazine (Phenergan): Adverse Effects

common—blurred vision, urinary retention, dry mouth, photosensitivity, drowsiness, & confusion.

Hydroxyzine (Vistaril, Atarax): Patient Teaching

instruct patients to take as directed & to enhance safety precautions due to adverse effects. Adverse effects may impair thinking or reactions, so operating a motor vehicle should be avoided.

Aprepitant (Emend): Patient Teaching

instructs patients to take medication as prescribed before onset of N/V. Alternate antiemetic medication (rescue antiemetic) may be necessary for who already have N/V.

Aprepitant (Emend): Contraindications

known hypersensitivity to drug or use in combination w/ ranolazine, pimozide, or cisapride.

Ondansetron (Zofran): Patient Teaching

may impair thinking or reactions; necessary to advise patients to use caution w/ driving or other tasks requiring mental alertness. Teach patients w/ phenylketonuria that oral disintegrating tablets contain phenylalanine

Aprepitant (Emend): Adverse Effects

most common—being fatigue, weakness, dizziness, abnormal heart rhythm, headache, & hiccups. Infusion site pain w/ IV administration.

Nausea and Vomiting: Causes

o GI disorders: infection/inflammation in the GI tract, liver, gallbladder, or pancreas; impaired GI motility & muscle tone (e.g., gastroparesis); & overeating or ingestion of foods/fluids that irritate GI mucosa. o Cardiovascular, infectious, neurologic, or metabolic disorders o Adverse effects of drug therapy; Although the symptoms may occur w/ most drugs, they are especially associated with alcohol, aspirin, digoxin, anticancer drugs, antimicrobials, estrogen preparations, and opioid analgesics. o Pain and other noxious stimuli, such as unpleasant sights and odors o Emotional disturbances; physical or mental stress o Radiation therapy o Motion sickness o Postoperative status, which may include pain, impaired GI motility, and receiving various medications o Pregnancy o Migraines

Aprepitant (Emend): Pharmacokinetics

o Orally absorbed, reaching peak levels 4 hours after administration; highly protein bound. o Metabolized: liver & Excreted: urine & feces. o Undergoes extensive hepatic metabolism by CYP450 enzyme systems, has potential for multiple drug interactions. o After administration, the IV form, fosaprepitant, is rapidly converted in the body to aprepitant.

Hydroxyzine (Vistaril, Atarax): Pharmacokinetics

o Orally, rapidly absorbed from GI tract, w/ its effect w/in 30 minutes. o Metabolized: liver, & main metabolite is cetirizine. Half-life: 14 hours for adults, 5 hours for small children, & 30 hours for elderly people. Excreted: urine in the form of its metabolites.

Nausea and Vomiting: Pathophysiology

o Vomiting occurs when vomiting center (a nucleus of cells in the medulla oblongata) is stimulated. Stimuli are relayed to the vomiting center by afferent signals from the chemoreceptor trigger zone (CTZ), cerebral cortex, the sensory organs, & vestibular apparatus. o The CTZ, composed of neurons in the 4th ventricle, can be activated by variety of stimuli (presence of emetic substances e.g., chemotherapy, opioids, ipecac) in blood & CSF & stimuli from pharynx & GI tract. o In chemotherapy, emetogenic drugs stimulate the release of serotonin from the enterochromaffin cells of the small intestine; this released serotonin then activates 5-HT3 receptors located on vagal afferent nerves in the CTZ to initiate the vomiting reflex. Activation of the CTZ is also thought to play a role in the N/V associated w/ pregnancy. o Anticipatory nausea triggered by memories & fear of N/V is mediated by afferent signals from the higher centers of the cerebral cortex to the vomiting center. Noxious stimuli such as unpleasant odors or sights as well as pain are transmitted by afferent pathways from the sensory organs to the vomiting center. In motion sickness, rapid changes in body motion stimulate receptors in the inner ear (vestibular branch of the auditory nerve, which is concerned w/ equilibrium), and nerve impulses are transmitted to the vomiting center. o The vomiting center, CTZ, & GI tract contain benzodiazepine, cholinergic, dopamine, histamine, opiate, substance Pneurokinin, & serotonin receptors, which are stimulated by emetogenic & toxins. When stimulated, vomiting center initiates efferent impulses that stimulate the salivary center; cause closure of the glottis, contraction of abdominal muscles & diaphragm, & relaxation of the gastroesophageal sphincter; & reverse peristalsis.

Ondansetron (Zofran): Pharmacokinetics

o Well absorbed from GI tract & undergoes some first-pass metabolism. Half-life: 3 to 5.5 hours in most, & 9 to 20 hours in moderate/severe liver impairment. o Orally, action begins in 30 to 60 minutes & peaks in 2 hours. o IV form, onset & peak are immediate. Bioavailability slightly increased by presence of food but unaffected by antacids.

Aprepitant (Emend): Assessing for Adverse Effects

observe for presence of adverse effects, such as fatigue, weakness, dizziness, headache, or hiccups. Additionally, it is necessary to assess for a normal heart rhythm.

Promethazine (Phenergan): Assessing for Therapeutic Effects

observe for prevention or resolution of nausea and vomiting.

Promethazine (Phenergan): Pharmacokinetics

orally, rapidly absorbed & undergoes extensive first-pass metabolism in the liver. Effects w/in 20 minutes after oral, IM, or rectal administration; the effects last 4 to 6 hours. Excretion in the urine.

Aprepitant (Emend): Use

part of combination therapy along w/ a 5-HT3 receptor antagonist & corticosteroids to treat both acute & delayed N/V associated w/ chemotherapy. o Other indications include prevention of postop N/V. FDA has stipulated that IV prodrug of oral formulation (fosaprepitant) should no longer be used to prevent N/V w/ chemotherapy due to the risk of abnormal heart rhythm. o Use in Children: well-tolerated in children receiving the drug in combination w/ standard antiemetics for chemotherapy-induced N/V. Additional evidence of efficacy is necessary in this population. o Use in Hepatic Impairment: No adjustment required. However, no data are available regarding use in people w/ severe hepatic impairment, & caution is warranted in cases of serious hepatic dysfunction. o Use in Patients With Critical Illness: The American Society of Clinical Oncology's antiemetic guidelines recommend the use of aprepitant in combination w/ serotonin receptor antagonist & dexa-methasone w/ chemotherapeutic drugs w/ high emetic risk. Also recommended as part of a chemotherapy regimen in protocols including anthracycline, cyclophosphamide, & other chemotherapeutic agents known to cause moderate emetic risk.

Ondansetron (Zofran): Use

prevent/treat moderate/severe N/V associated w/ cancer chemotherapy, radiation therapy, & postoperative status. o Use in Children: indicated for use; little information available about its use younger than 6 months. The American Society of Clinical Oncology recommends use of 5-HT3 receptor antagonist plus a corticosteroid before administering high-dose chemotherapy or chemotherapy w/ high to moderate emetic risk to pediatric oncology patients. o Use in Hepatic Impairment: half-life is increased. Increases risk of adverse effects. o Use in Patients Receiving Home Care: Oral administration may be given. Assesses for resolution of N/V. Diarrhea is a common adverse effect; therefore, assist w/ use of the drugs & interventions to prevent fluid & electrolyte depletion.

Promethazine (Phenergan): Use

prevention/treatment of N/V associated w/ surgery, anesthesia, migraines, chemotherapy, & motion sickness. o Use in Children: BLACK BOX WARNING alerts nurses that promethazine is contraindicated in children younger than 2 years of age because of the risk of potentially fatal respiratory depression. Additionally, promethazine should not be used in children with hepatic disease, Reye's syndrome, a history of sleep apnea, or a family history of sudden infant death syndrome. o Use in Older Adults: increased concerns with the adverse anticholinergic effects (e.g., dizziness, acute confusion, delirium, dry mouth, tachycardia, blurred vision, urinary retention, constipation). o Use in With Renal Impairment: dose reduction may be necessary in renal impairment to avoid possibility of adverse effects, toxicity, or increased sensitivity to phenothiazines. o Use in Hepatic Impairment: the presence of liver disease (e.g., cirrhosis, hepatitis) may slow metabolism & prolong drug elimination half-life, w/ resultant accumulation & increased risk of adverse effects. Drug should be used cautiously in hepatic impairment. Cholestatic jaundice may occur.

Hydroxyzine (Vistaril, Atarax): Action

relieve nausea and vomiting by blocking the action of acetylcholine in the brain.

Aprepitant (Emend): Administering Medications

take by mouth as directed with full glass of water, w/ or w/out food. First dose is taken 1 hour before chemotherapy & then daily in the morning for the next 2 days after chemotherapy treatment. Recently approved IV form (fosaprepitant), as a dose of 115 mg, is bioequivalent to aprepitant, 125 mg, & it is appropriate to use these forms interchangeably.

Hydroxyzine (Vistaril, Atarax): Use

treating N/V & preventing & treating motion sickness. Also used as a sedative to treat anxiety. Additionally, the drug is given in combination with other medications during anesthesia. o Use in Children: the recommended dosage is based on age & weight. o Use in Older Adults: According to Beers Criteria, hydroxyzine is considered inappropriate for use in older adults. Dosage reduction may be appropriate due to an increased sedative potential. o Use in Renal Impairment: dosage adjustments & intensive monitoring of adverse effects may be required. o Use in Hepatic Impairment: dosage adjustments & intensive monitoring of adverse effects may be required. o Use in Patients Receiving Home Care: usually given orally or rectal in home setting. Home care nurse need to assess for possible causes of N/V & assist w/ appropriate use of drugs & other interventions to prevent fluid & electrolyte depletion. Excessive sedation may occur w/ usual doses of & is more likely w/ high doses. May be minimized by avoiding high doses & assessing patient's LOC before dose. Teach safety precautions w/ sedating drugs.

Promethazine (Phenergan): Patient Teaching

use lowest effective dosage & do not take drugs w/ respiratory depressant effects concurrently.

Ondansetron (Zofran): Adverse Effects

usually mild to moderate' diarrhea, headache, dizziness, constipation, fatigue, transient elevation of liver enzymes, & pain at the injection site. Contraindications include known hypersensitivity to the drug.

Nonpharmacologic Management

• Acupuncture and Acupressure: acupuncture is one of the most well-studied & accepted forms of treatment of postoperative N/V, although the mechanism remains unclear. Use of acupressure wristbands has also been useful in the treatment of N/V associated w/ motion sickness. • Herbal Supplements: Use of ginger in traditional Chinese and Indian medicine. Clinical trials indicate that herb can reduce N/V associated w/ motion sickness, pregnancy, & surgery. Evidence of the herb's success against chemotherapy-induced N/V is mixed. The herb's components interact w/ 5-HT3 receptors, which may account for the antiemetic activity.

Antihistamines

• Antihistamines used primarily to prevent histamine from exerting its widespread effects. • Antihistamines used as antiemetic agents are the "classic" antihistamines or H1 receptor blocking agents. • Not all antihistamines are effective as antiemetic agents. Hydroxyzine (Vistaril, Atarax) is the prototype of the class.

Promethazine (Phenergan)

• CNS depressants used for a variety of reasons, including prevention/treatment of N/V. • Dosage and route of depend on reason for use. Doses of phenothiazines are much smaller for antiemetic effects than for antipsychotic effects; not all phenothiazines are effective antiemetics. • Promethazine (Phenergan), w/ its antiemetic action, is the prototype.

Miscellaneous Antiemetics

• Corticosteroids are used mainly as antiallergic, anti-inflammatory, & antistress agents, they have antiemetic effects as well. Dexamethasone & methylprednisolone are commonly used in management of chemotherapy-induced emesis & postoperative N/V, either alone or in combination w/ 5-HT3 receptor antagonists &/or substance P/neurokinin 1 receptor antagonists. W/ short-term use, adverse effects associated w/ corticosteroids are mild (e.g., euphoria, insomnia, mild fluid retention). • Benzodiazepine antianxiety drugs are not antiemetics, but they are often used in multidrug regimens to prevent N/V associated w/ chemotherapy. Prescribed for patients who experience anticipatory N/V before administration of anticancer drugs. Lorazepam (Ativan) is commonly used for this purpose. • Dronabinol is a cannabinoid (derivative of marijuana) used in the management of N/V associated w/ anticancer drugs & unrelieved by other drugs. (Schedule III) • Marijuana cigarettes have been used by some people to treat chemotherapy-induced N/V. • Phosphorated carbohydrate solution (Emetrol) is a hyperosmolar solution w/ phosphoric acid. Thought to reduce smooth muscle contraction in the GI tract & is available as OTC medication in syrup form. o QSEN: Because this solution contains fructose, patients with diabetes mellitus should consult their health care provider before using it. • Scopolamine, an anticholinergic drug effective in relieving N/V associated w/ motion sickness & radiation therapy. Available as a transdermal patch, which is often used to prevent motion sickness.

Promethazine (Phenergan): Preventing Interactions

• Herbal interactions: kava kava, St. John's wort, and valerian; an increased risk of CNS depression is a possibility. • Drugs That Increase Effects: Escitalopram → Has additive respiratory depressant effects • Ethanol → Increases the risk of CNS depression & psychomotor impairment • Duloxetine → Increases the plasma concentration • Gabapentin → Has additive respiratory depressant effects • Zolpidem →H as additive respiratory depressant effects

Ondansetron (Zofran): Preventing Interactions

• Phenytoin, carbamazepine, rifampin, & other inducers of the cytochrome 450 (CYP) 3A4 enzymes increase the clearance of ondansetron & decrease serum concentrations. • Use of ondansetron w/ apomorphine is contraindicated due to the potential of a significant drop of BP or loss of consciousness w/ concurrent use. St. John's wort may decrease ondansetron levels.

Promethazine (Phenergan): Other Drugs in Class

• Prochlorperazine (Compazine), which has side effects similar to promethazine, is used in treatment of severe N/V associated w/ anesthesia. • Chlorpromazine (Thorazine) (more commonly used in treatment of psychosis & psychotic symptoms in other disorders), is also used w/ intractable hiccups & treatment of N/V associated w/ anesthesia. • Perphenazine (Trilafon) is used to manage intractable hiccups and severe nausea and vomiting.

Aprepitant (Emend): Preventing Interactions

• Reduce oral doses of dexamethasone or methylprednisolone by 50% & IV dose of methyl-prednisolone by 25% when coadministered w/ aprepitant due to CYP3A4 inhibition. • Eeduces the effectiveness of oral contraceptives for up to 28 days after administration; alternate contraceptive methods are recommended during treatment & for 1 month following administration of aprepitant. • QSEN: prepitant induces the metabolism of warfarin. It is necessary to monitor the international normalized ratio for 2 weeks after treatment is initiated, especially for the first 7 to 10 days. • Drugs That Increase Effects: CYP3A4 inhibitors, such as macrolide antibiotics, pro-tease inhibitors, azole antifungal agents, nefazodone, cyclosporine, danazol, diltiazem, and verapamilAlter metabolism → increasing serum levels • Drugs That Decrease the Effects: rs, such as carbamazepine, phenyt-oin, rifampin, phenobarbital, and nevirapine → Alter metabolism, decreasing serum levels • Grapefruit juice increases the serum levels of aprepitant. St. John's wort cause a decrease in serum levels.

Hydroxyzine (Vistaril, Atarax): Preventing Interactions

• Several medications that can cause CNS depression, such as sedatives, tranquilizers, muscle relaxants, & antidepressants, can have an increased sedative effect with the concomitant use of hydroxyzine. • Drugs That Increase the Effects: Alcohol → Increases the risk of respiratory depression • Gabapentin, levetiracetam, lamotrigine → Increase the risk of respiratory depression • Seroquel → Increases the risk of severe extrapyramidal reactions

Patient Teaching Guidelines: Antiemetic Drugs Self- or Caregiver Administration

• Take the drugs as prescribed. Do not increase dosage, take more often, or take when drowsy, dizzy, or unsteady on your feet. Several of the drugs cause sedation and other adverse effects, which are more severe if too much is taken. • To prevent motion sickness, take medication 30 minutes before travel & then every 4 to 6 hours, if necessary, to avoid or minimize adverse effects. • Take or give drugs 30 to 60 minutes before a nausea-producing event, when possible. This includes cancer chemotherapy, radiation therapy, changing of painful dressings, or other treatments. • Take dronabinol only when you can be supervised by a responsible adult because of its sedative & mind-altering effects. • Aprepitant (Emend) reduces the effectiveness of oral contraceptives; therefore, use an alternative form of birth control during therapy and for 1 month after therapy.