drugs n/v

Hydroxyzine (Vistaril) action:

Hydroxyzine and other antihistamines are thought to relieve nausea and vomiting by blocking the action of acetylcholine in the brain.

Promethazine (Phenergan) use in the pts w renal impairment:

A dose reduction may be necessary in patients with renal impairment to avoid the possibility of adverse effects, toxicity, or increased sensitivity to phenothiazines.

Phenothiazines:

-Phenothiazines are first-generation (typical) antipsychotic drugs that depress the central nervous system (CNS). -The first group of drugs to exhibit extensive activity in the prevention of chemotherapy-induced emesis, they are also used to treat schizophrenia or psychosis -These drugs act primarily by antagonizing D2-dopamine receptors in the area postrema of the midbrain, therefore decreasing the effect of dopamine in the brain. They also possess M1-muscarinic and H1-histamine blocking effects. Doses of phenothiazines are much smaller for antiemetic effects than for antipsychotic effects; not all phenothiazines are effective antiemetics

Hydroxyzine (Vistaril) use in the older adults:

According to the Beers Criteria (see Chap. 5), hydroxyzine is considered potentially inappropriate for use in older adults. Dosage reduction may be appropriate with older adults due to an increased sedative potential.

Ondansetron (Zofran) adverse effects:

Adverse effects of ondansetron are usually mild to moderate. Common ones include diarrhea, headache, dizziness, constipation, fatigue, transient elevation of liver enzymes, and pain at the injection site.

Drugs That Increase the Effects of Hydroxyzine:

Alcohol, gabapentin, levetiracetam, and lamotrigine Seroquel

timuli are then relayed to the vomiting center by afferent signals from the chemoreceptor trigger zone (CTZ), as well as the cerebral cortex, the sensory organs, and the vestibular apparatus. The CTZ, composed of neurons in the fourth ventricle, can be activated by a variety of stimuli, including the presence of emetic substances (e.g., toxins, chemotherapy, opioids, ipecac) in the blood and cerebrospinal fluid and stimuli from the pharynx and GI tract. In cancer chemotherapy, emetogenic drugs are thought to 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 nausea and vomiting associated with pregnancy.

Anticipatory nausea and vomiting triggered by memories and fear of nausea and vomiting 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 with equilibrium), and nerve impulses are transmitted to the vomiting center.

Hydroxyzine (Vistaril) use in the pts reciving home care:

Antiemetics are usually given orally or by rectal suppository in the home setting. The home care nurse may need to assess patients for possible causes of nausea and vomiting and assist patients and caregivers with appropriate use of the drugs and other interventions to prevent fluid and electrolyte depletion. Excessive sedation may occur with usual doses of antiemetics and is more likely with high doses. This may be minimized by avoiding high doses and assessing the patient's level of consciousness before each dose. Teaching safety precautions with sedating drugs may also be needed.

ANTIHISTAMINES: What is the prototype?

Antihistamines are used primarily to prevent histamine from exerting its widespread effects on body tissues (see Chap. 32). The antihistamines used as antiemetic agents are the "classic" antihistamines or H1 receptor blocking agents (as differentiated from cimetidine and related drugs, which are H2 receptor blocking agents). Not all antihistamines are effective as antiemetic agents -Hydroxyzine (Vistaril)

assessing for adverse effects of Ondansetron (Zofran):

Because headache and diarrhea are the most common adverse effects, the nurse gives special attention when assessing for these effects. It is also necessary to evaluate for stamina and balance. The nurse should note that use of ondansetron may mask a progressive ileus and gastric distension following abdominal surgery or in patients with chemotherapy-induced nausea and vomiting.

Hydroxyzine (Vistaril) use in renal pts:

Because hydroxyzine is excreted in the urine, dosage adjustments and more intensive monitoring of adverse effects may be required in people with renal impairment.

Contraindications Hydroxyzine (Vistaril) :

Contraindications to hydroxyzine include known sensitivity to the drug.

Promethazine (Phenergan) contraindications:

Contraindications to use of promethazine include known hypersensitivity to the drug. Cautious use is necessary in people with glaucoma because the drug possesses antimuscarinic activity.

Ondansetron (Zofran) use in the older adults:

Dosage adjustment is not required in patients older than 65 years of age. Researchers have observed no overall differences in safety or effectiveness in older adults compared with younger patients.

Drugs That Increase the Effects of Promethazine:

Escitalopram, gabapentin, and zolpidem Ethanol Duloxetine

Hydroxyzine (Vistaril) use:

Hydroxyzine may be effective in treating nausea and vomiting and preventing and treating motion sickness. Hydroxyzine is also used as a sedative to treat anxiety. Additionally, the drug is given in combination with other medications during anesthesia.

Drug Therapy Antiemetic drugs are indicated to prevent and treat nausea and vomiting associated with surgery, pain, motion sickness, cancer chemotherapy, radiation therapy, pregnancy, and other causes. Several classes of these drugs are available, which antagonize the neurotransmitter receptors that play a role in the physiology of nausea and vomiting by acting on the vomiting center, CTZ, cerebral cortex, vestibular apparatus, or a combination of these. The antiemetic drugs in this chapter are classified according to their primary action. However, some agents affect multiple receptors.

In general, the drugs are more effective in prophylaxis than treatment. Most antiemetic agents are available in oral, parenteral, and rectal dosage forms. As a general rule, oral forms are preferred for prophylactic use, and rectal or parenteral forms are preferred for therapeutic use. Prompt treatment of vomiting is more effective than is managing long-term vomiting. Nurses should be aware that pregnant women should not take any medication without the guidance of their health care provider. Some antiemetics are dangerous during pregnancy and can cause damage to the fetus. However, when the nausea and vomiting associated with pregnancy are not controlled with lifestyle measures, some pharmacologic interventions may be appropriate.

administering Ondansetron (Zofran):

It is 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

Hydroxyzine (Vistaril) use in hepatic pts:

Likewise, because hydroxyzine is metabolized in the liver, dosage adjustments and more intensive monitoring of adverse effects may be required in people with hepatic impairment.

Describe the other drugs in this class: Diphenhydramine, dimenhydrinate (Dramamine), and meclizine (Dramamine Less Drowsy, Motion-Time) are also used to prevent nausea, vomiting, dizziness, and vertigo associated with motion sickness.

Meclizine is also given to manage vertigo associated with disease affecting the vestibular system. Dimenhydrinate is available over the counter, and meclizine is dispensed by prescription. The initial dose should be taken 1 hour prior to travel to reduce the risk of motion sickness. Thereafter, the dose may be repeated every 24 hours for the duration of the travel. For vestibular diseases, meclizine should be taken at the onset of symptoms. As with hydroxyzine, it is necessary to instruct patients taking dimenhydrinate to use caution while driving, operating machinery, or performing other hazardous activities due to the associated drowsiness. (The addition of theophylline to the formulation is designed to counteract drowsiness.) Dimenhydrinate typically takes a minimum of 4 hours to take full effect. Meclizine becomes effective in about 1 hour. This drug is less likely to cause drowsiness, but people taking the drug should use caution when participating in hazardous activities and avoid using alcohol.

Promethazine (Phenergan) use in the older adults:

Older adults may have increased concerns with the adverse anticholinergic effects (e.g., dizziness, acute confusion, delirium, dry mouth, tachycardia, blurred vision, urinary retention, constipation).

Ondansetron (Zofran) action:

Ondansetron and the other 5-HT3 receptor antagonists antagonize serotonin receptors, preventing their activation by the effects of emetogenic drugs and toxins

Ondansetron (Zofran) use:

Ondansetron is used to prevent or treat moderate to severe nausea and vomiting associated with cancer chemotherapy, radiation therapy, and postoperative status.

Administering Hydroxyzine (Vistaril) :

Oral administration of hydroxyzine is often unsuccessful with nausea and vomiting. It is important to give the medication intramuscularly deep into a large muscle, not subcutaneously. IV administration can result in a sterile abscess with damage to tissue.

Ondansetron (Zofran) use in the pt recieivng home care:

Oral administration of the drug may be given in the home setting. The home care nurse assesses for resolution of nausea and vomiting. Diarrhea is a common adverse effect; 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.

Preventing interactions with hydroxyzine (vistaril) :

Several medications that can cause CNS depression, such as sedatives, tranquilizers, muscle relaxants, and antidepressants, can have an increased sedative effect with the concomitant use of hydroxyzine. No herbs or foods appear to decrease or increase the effects of hydroxyzine.

Ondansetron (Zofran) pharmacokinetics:

Oral ondansetron is well absorbed from the GI tract and undergoes some first-pass metabolism. The drug's half-life is 3 to 5.5 hours in most patients and 9 to 20 hours in patients with moderate or severe liver impairment. With the oral form, action begins in 30 to 60 minutes and peaks in about 2 hours. With the IV form, onset and peak of drug action are immediate. The bioavailability is slightly increased by the presence of food but is unaffected by antacids.

Promethazine (Phenergan) use in the hepatic pt:

Phenothiazines are metabolized in the liver. Therefore, the presence of liver disease (e.g., cirrhosis, hepatitis) may slow metabolism and prolong drug elimination half-life, with resultant accumulation and increased risk of adverse effects. Thus, the drugs should be used cautiously in patients with hepatic impairment. Cholestatic jaundice may occur with promethazine.

Ondansetron (Zofran) preventing interactions:

Phenytoin, carbamazepine, rifampin, and other inducers of the cytochrome 450 (CYP) 3A4 enzymes increase the clearance of ondansetron and decrease serum concentrations. No dosage adjustment of ondansetron appears necessary for people taking these drugs based on available data. The use of ondansetron with apomorphine is contraindicated due to the potential of a significant drop of blood pressure or loss of consciousness with concurrent use. St. John's wort may decrease ondansetron levels.

Acupuncture and Acupressure:

Practitioners use acupuncture and acupressure to stimulate the pericardium 6 site, which is generally thought to be effective in the management of chemotherapy-induced nausea and vomiting and motion sickness. Acupuncture is one of the most well studied of all the nonpharmacologic techniques, but interpretation of the results of randomized trials is hampered by a high risk of bias in most studies and a lack of standardization of treatment methods and comparison groups. Acupressure wristbands may also be useful in the treatment of nausea and vomiting associated with motion sickness.

Phenothiazines, prototype?

Promethazine (Phenergan)

Promethazine (Phenergan) action:

Promethazine and other phenothiazines have widespread effects on the body. The therapeutic effects in nausea and vomiting are attributed to their ability to block dopamine from receptor sites in the brain and CTZ.

Promethazine (Phenergan) pharmacokinetcs:

Promethazine is rapidly absorbed following oral administration and undergoes extensive first-pass metabolism in the liver. Clinical effects are apparent within 20 minutes after oral, intramuscular, or rectal administration; the effects last 4 to 6 hours. Metabolism occurs in the liver, with excretion in the urine.

Promethazine (Phenergan) use:

Promethazine is used for the prevention and treatment of nausea and vomiting associated with surgery, anesthesia, migraines, chemotherapy, and motion sickness.

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

The 5-HT3 receptor antagonists approved for use in the United States are the cornerstones of therapy for the control of acute emesis caused by chemotherapy agents with moderate to high emetogenic potential. In addition, the class is usually considered drugs of first choice for postoperative nausea and vomiting. -Ondansetron (Zofran)

Adminsitering Promethazine (Phenergan):

The FDA has issued a BLACK BOX WARNING ♦ alerting nurses that promethazine is contraindicated for subcutaneous administration. The preferred parenteral 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 avoids intravenous (IV) administration, if possible, because the drug can cause severe tissue injury.

patient teaching for Ondansetron (Zofran):

The drug may impair thinking or reactions, which means that it is necessary to advise patients to use caution with driving or other tasks requiring mental alertness. The nurse teaches patients with phenylketonuria that the oral disintegrating tablets contain phenylalanine. Box 38.2 presents other patient teaching guidelines.

Ondansetron (Zofran) use in hepatic pts:

The drug's half-life is significantly increased in patients with moderate to severe hepatic impairment. This increases the risk of adverse effects.

Assessing for adverse effects of Promethazine (Phenergan):

The nurse assesses for associated adverse anticholinergic effects (dry mouth, blurred vision, urinary retention, constipation, acute confusion, dizziness, tachycardia). It is necessary to be aware that hallucinations, convulsions, and sudden death may occur with excessive doses. The nurse also assesses tissue integrity with injection of the drug because the drug may cause severe tissue injury; burning and pain at the IV site justify immediate discontinuation of the drug.

Assessing for therpatuic effects of Hydroxyzine (Vistaril) :

The nurse assesses for the absence of nausea and vomiting.

Assessing for adverse effects of Hydroxyzine (Vistaril) :

The nurse assesses for the presence of anticholinergic effects, including blurred vision, urinary retention, constipation, thick secretions, and blurred vision. Patients with narrow-angle glaucoma, prostatic hyperplasia, and asthma are at greater risk for adverse effects.

assessing for theraputic effects of Ondansetron (Zofran):

The nurse assesses for verbal reports of decreased nausea and the absence of vomiting.

Teaching for Hydroxyzine (Vistaril):

The nurse instructs patients to take medication as directed and to enhance safety precautions due to adverse effects. Adverse effects may impair thinking or reactions, so operating a motor vehicle should be avoided. Box 38.2 outlines additional patient teaching guidelines.

Assessing for theraputic effects of Promethazine (Phenergan):

The nurse observes for prevention or resolution of nausea and vomiting.

Patient teaching for Promethazine (Phenergan):

The nurse teaches patients taking promethazine to use the lowest effective dosage and not to take other drugs with respiratory depressant effects concurrently. Box 38.2 presents additional patient teaching guidelines. page 750

Describe the other drug in this class: Dolasetron (Anzemet)

The other 5-HT3 receptor antagonist drugs may be less beneficial as rescue drugs in the treatment of chemotherapy-induced nausea and vomiting and more effective in the prevention of this condition. Dolasetron (Anzemet) may be given intravenously or orally. The oral route of dolasetron is approved for chemotherapy-related nausea and vomiting; the IV route is only used for prevention of postoperative nausea and vomiting. As with ondansetron, other 5-HT3 receptor antagonists are associated with dose-dependent increases in electrocardiographic intervals, including PR, QRS duration, and QT interval. These drugs should be avoided in patients taking class I and class III antidysrhythmic agents because of concerns about the development of torsades de pointes, with prolongation of the QT interval

Herbal Supplements :

The use of ginger in traditional Chinese and Indian medicine has a long history. Clinical trials indicate that the herb can effectively reduce nausea and vomiting associated with motion sickness, pregnancy, and surgery. Evidence of the herb's success against chemotherapy-induced nausea and vomiting is mixed. The herb's components are thought to interact with 5-HT3 receptors, which may account for the antiemetic activity.

Patho vomitting:

Vomiting occurs when the vomiting center (a nucleus of cells in the medulla oblongata) is stimulated (Fig. 38.1). Five neurotransmitter receptors are significantly involved in the vomiting reflex; these include the muscarinic (M1), dopamine (D2), histamine (H1), 5-hydroxytryptamine3 (5-HT3), and substance P/neurokinin 1 (NK1) receptors. 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, and relaxation of the gastroesophageal sphincter; and reverse peristalsis, which moves stomach contents toward the mouth for ejection.

Hydroxyzine (Vistaril) pharmacokinetics:

When administered orally, hydroxyzine is rapidly absorbed from the GI tract, with its effect noticeable within 30 minutes. The drug is metabolized in the liver, and the main metabolite is cetirizine. The half-life of hydroxyzine is, on average, 14 hours for adults, but it can be as short as 5 hours for small children and as long as 30 hours for elderly people. Hydroxyzine is excreted into the urine in the form of its metabolites.

Adverse effects of Hydroxyzine (Vistaril):

With hydroxyzine, adverse anticholinergic effects include drowsiness, dizziness, confusion, dry mouth, thickened respiratory secretions, blurred vision, urinary retention, and tachycardia

Promethazine (Phenergan) adverse effects:

With promethazine, common side effects include blurred vision, urinary retention, dry mouth, photosensitivity, drowsiness, and confusion.

Scopolamine (Transderm):

an M1 muscarinic receptor antagonist, is a major anticholinergic drug (see Chap. 48) effective in relieving nausea and vomiting associated with motion sickness and radiation therapy. It is predominately used as a transdermal patch to prevent motion sickness.

Ondansetron (Zofran) contraindications:

hypersensitivity

MISCELLAENOUS ANTIEMETICS : Cannabinoids (derivatives of marijuana) have demonstrated modest antiemetic activity. However, concern about their abuse potential and their rather unfavorable adverse effect profiles, especially in older adults, have limited their clinical utility. The cannabinoid dronabinol (Marinol)... DESCRIBE :

is approved in patients who have failed to respond adequately to conventional antiemetic treatments, and national clinical practice guidelines propose that this agent be considered as a rescue antiemetic for refractory nausea and vomiting. Onset of action occurs within 12 hours, with peak intensity within 24 hours and dissipation within 96 hours. Dronabinol has the same adverse effects as marijuana, including psychiatric symptoms, and a high potential for abuse. In addition, the drug may cause a withdrawal syndrome when abruptly discontinued. Thus, it is a Schedule III drug under federal narcotic laws. Withdrawal symptoms (e.g., insomnia, irritability, restlessness) are most likely to occur with high doses or prolonged use, and sleep disturbances may persist for several weeks.

Preventing interactions: Herbal interactions with promethazine have been reported with :

kava kava, St. John's wort, and valerian; an increased risk of CNS depression is a possibility.

Antiemetic drugs are used to prevent or treat nausea and vomiting. They are usually contraindicated if their use:

may prevent or delay diagnosis or may mask signs and symptoms of drug toxicity.