Antiemetics

Definition

Antiemetic drugs are drugs used to combat nausea and vomiting .

Purpose

Antiemetic drugs are used to prevent vomiting (emesis) in chemotherapy patients and postoperative patients. Aside from the difficulty of maintaining proper nutrition and a healthy weight, chronic vomiting can result in dehydration, which can be a medical emergency. Following are descriptions of antiemetic drugs in use as of 2001.

Description

Promethazine

Promethazine is also known as phenergan and mepergan. It is also used to treat motion sickness, reduce allergic symptoms, and for sedation. It is one of the drugs of the phenothiazine type. In addition to other qualities, it is an antihistamine.

Prochlorperazine

Prochlorperazine is also known as compazine. Like promethazine, it is a member of the class of phenothiazines. Unlike promethazine, however, prochlorperazine also belongs to the class of drugs known as antipsychotics, or neuroleptics. Antipsychotic drugs are used to treat psychoses and other psychiatric disorders. In addition to its use as an antiemetic and anti-psychotic drug, prochlorperazine is also used to treat non-psychotic anxiety.

Serotonin receptor antagonists

The serotonin receptor antagonists include granisetron (kytril), dolasetron (anzemet), and ondansetron (zofran). These drugs are used for postoperative nausea and emesis as well as nausea and vomiting associated with chemotherapy, and are often used in combination with a corticosteroid. Ondansetron is approved for nausea and vomiting associated with radiation therapy .

Dronabinol

Dronabinol (marinol) is used to combat anorexia in AIDS patients, and emesis in cancer patients who haven't responded to other antiemetics. Marinol is the synthetic or extracted form of the active ingredient found in marijuana .

Other antipsychotic (neuroleptic) drugs

The other neuroleptic (antipsychotic) drugs used to treat nausea and emesis are droperidol (inapsine), haloperidol (haldol), chlorpromazine (thorazine), and perphenazine (trilafon). One other antipsychotic, triethylperazine (torecan or norzine), was used as an antiemetic, but is no longer widely available. Some of the antipsychotics are also used to treat aggressive or violent behavior or intractable hiccups (chlorpromazine). These drugs are similar to prochlorperazine in terms of their actions and potentially severe side effects.

There are some additional precautions and side effects associated with each of these drugs. Patients should be sure to notify their physician of any health concerns (including pregnancy) or medications they are taking. Patients should also ask about potential side effects for each individual medication before receiving any of these drugs.

Dosage

Promethazine

Promethazine is given in doses of 12.5 to 25 mg every 4 hours if injected into the muscle or as a suppository. As a syrup, 25 mg should be given every 4 to 6 hours. Doses for children vary by age, weight, and severity of condition.

Prochlorperazine

Generally, the dose is 5 to 10 mg, 3 to 4 times per day. However, the effect of medication varies widely from patient to patient, so the dose should be tailored to each individual. Prochlorperazine is available as a syrup, tablet, 25 mg slow-release capsule, and in injectable form.

Dronabinol

The effective dose of dronabinol varies widely from patient to patient and should be monitored and tested by the physician. The basic dose is 5mg/m ² given 4 to 6 times per day.

Precautions

Promethazine

Patients with cardiovascular disease or impaired liver function should either use this drug with caution or not at all. Children should also use this drug cautiously for two reasons. First, some side effects may suggest, or mask, underlying disease, such as Reye's syndrome. Second, large doses of this drug, or any antihistamine, may cause convulsions, hallucinations, or death in children. Patients taking this medication should not drive, operate heavy machinery, or engage in any hazardous activity while under the influence of this drug. This drug has not been established as safe for use during pregnancy, or in nursing mothers.

Prochlorperazine

Persons allergic to any other phenothiazine (such as promethazine) should not take prochlorperazine. Patients who have heart problems, glaucoma or bone marrow depression should take this drug with caution, or not at all, and inform their physician of their condition. Persons who will be around high temperatures should also avoid this drug. In addition, persons who experience seizures should be aware that administration of this drug makes seizures more likely.

Breast cancer patients may wish to avoid this drug because it increases levels of prolactin in the blood. Increased prolactin may help some types of breast cancer to thrive.

Prochloroperazine, like promethazine, may mask symptoms of Reye's disease in children. It may also mask symptoms of intestinal obstructions or brain disease. In addition, children who are acutely ill, under two years of age, or under 20 pounds should not be given this drug.

This drug has not been established as safe for use during pregnancy and is found in the breast milk of lactating mothers. Therefore, caution should be used when administering this drug to pregnant women and extreme caution should be used when administering to nursing women.

Serotonin receptor antagonists

Patients with allergies to any drug in this category should not take any other drug in this category. Also, patients with hypokalemia, hypomagnesia, or certain heart problems should avoid taking these drugs. The effect of these drugs on the children or fetuses of nursing or pregnant mothers is not known, so they should be used with caution.

Dronabinol

Dronabinol is inadvisable for patients with a known allergy to either sesame oil or any part of the cannabis plant. Patients taking this drug should not drive, operate heavy machinery, or engage in hazardous tasks until used to this medication.

This medication also should be used cautiously, if at all, for persons with depression, mania, or schizophrenia, elderly patients, patients with cardiac disorders, and for pregnant and nursing women. It is especially inadvisable for nursing women, since marinol is concentrated in the breast milk.

Side effects

Promethazine

Patients taking promethazine may experience a large number of side effects, including drowsiness, ringing in the ears, a lack of coordination, problems with vision, fatigue , euphoria, nervousness, tremors, seizures, a cata-tonic-like state, and hysteria. These effects are usually reversible. At high doses, patients may also exhibit extrapyramidal reactions. Extrapyramidal reactions can briefly be described as agitation (jitteriness, sometimes insomnia), muscle spasms, and/or pseudo-Parkinson's (a group of symptoms including, but not limited to, drooling, tremors, and a shuffling gait).

Patients may also experience rashes, asthma, jaundice, abnormally low production of white blood cells, and abnormalities in how fast or slow their heart beats. Patients may sometimes experience unusual side effects not known as typical for the medication they are taking. These should be reported to the physician.

Prochlorperazine

Prochlorperazine has many side effects, including low blood pressure, dizziness, blurred vision, skin reactions, jaundice, lack of production of white cells, damage to the DNA in sperm, problems in the regulation of body temperature, impotence, amenorrhea (a lack of menstruation), and gynecomastia (the growth of female-like breasts in males). However, the most severe side effects stem from damage to the brain. Patients may suffer from extrapyramidal reactions. These symptoms may be reversed by treating the patient with drugs effective in treatment of Parkinson's patients (except levodopa). A reduction or elimination in the amount of the antipsychotic medication may also be necessary to eliminate these symptoms.

Two other (rare) disorders, tardive dyskinesia and neuroleptic malignant syndrome (NMS), are also associated with antipsychotic drug use. Patients with NMS have high temperatures, rigid muscles, an altered mental state, and symptoms such as excessive sweating and irregular blood pressure or heart rhythm. Patients with NMS usually respond to treatment. Patients with tardive dyskinesia have involuntary movement of muscles in the chest, arms, and legs, or in the muscles in and around the face (including the tongue). Tardive dyskinesia may be irreversible.

Serotonin receptor antagonists

Side effects include rashes, increased sweating, problems with taste or vision, flushing, agitation, sleep disorder, depersonalization, headache, fatigue, nausea, weakness, abdominal pain, constipation, diarrhea , hypertension, dizziness, chills and shivering, and dry mouth. Patients may also have abnormal liver function tests.

Dronabinol

Possible side effects are fatigue, weakness, abdominal pain, nausea, vomiting, heart palpitations, fast heart rate, facial flushing, amnesia, anxiety, an abnormal mental state, depersonalization, confusion, dizziness, and euphoria.

Interactions

Promethazine

Promethazine interacts with central nervous system depressants, like alcohol and barbiturates. Therefore, the physician should alerted to any medications the patient is taking, and doses of the drugs should be adjusted accordingly. Alcohol should be avoided. It has not been proven, but promethazine may interfere with the action of epinephrine.

Prochlorperazine

Like promethazine, prochlorperazine should be used cautiously, or not at all, with central nervous system depressants like alcohol and barbiturates. Prochlorperazine has also been shown to interact with anticonvulsant medication, guanethidene, propanolol, thiazide diuretics, and oral anticoagulants (like warfarin and coumadin).

Serotonin receptor antagonists

These drugs may have very negative effects on the patient when combined with diuretics, anti-arrhythmia drugs, or high doses of anthracycline.

Dronabinol

Dronabinol interacts with the antiemetic prochlorperazine synergistically. Therefore, the use of these two drugs in combination results in a greater antiemetic effect. Patients taking central nervous system depressants, such as barbiturates or alcohol should notify their physician before taking marinol, since marinol may increase their effect. Although no drugs have been shown to interact with marinol, many drugs similar to marinol do interact with a number of other drugs, including central nervous system depressants such as alcohol or barbiturates, or drugs like flouxetine or disulfiram. Again, the physician should alerted to any medications the patient is taking before beginning a course of dronabinol.

See Also Corticosteroids; Lorazepam; Metoclopramide; Scopolamine

Michael Zuck, Ph.D.

KEY TERMS

Depersonalization

—An alteration in the perception of self.

Tardive dyskinesia

—A disorder brought on by antipsychotic medication use, and is characterized by uncontrollable muscle spasms.

Antinausea Drugs

Definition

Antinausea drugs are medicines that control nausea—a feeling of sickness or queasiness in the stomach with an urge to vomit. These drugs also prevent or stop vomiting. Drugs that control vomiting are called antiemetic drugs.

Purpose

Antinausea drugs such as prochlorperazine (Compazine), usually control both nausea and vomiting. Prochlorperazine is also sometimes prescribed for symptoms of mental disorders, such as schizophrenia.

Another commonly prescribed antinausea drug is promethazine (Phenergan). Promethazine also may be prescribed to relieve allergy symptoms and apprehension, as well as motion sickness.

Description

Prochlorperazine is available only with a physician's prescription. It is sold in syrup, capsule, tablet, injection, and suppository forms.

Recommended dosage

To control nausea and vomiting in adults, the usual dose is:

• Tablets—one 5-mg or 10-mg tablet three to four times a day
• Extended-release capsules—one 15-mg capsule first thing in the morning or one 10-mg capsule every 12 hours
• Suppository—25 mg, twice a day

• Syrup—5-10 mg three to four times a day
• Injection—5-10 mg injected into a muscle three to four times a day.

Doses for children must be determined by a physician.

Promethazine may be administered in pill, syrup, chewable tablet, or extended release capsule form by prescription only. For severe nausea, it may be administered by injection or via a suppository. The physician recommends dose depending on the patient's condition.

KEY TERMS

Anesthetic— Medicine that causes a loss of feeling, especially pain. Some anesthetics also cause a loss of consciousness.

Antihistamine— Medicine that prevents or relieves allergy symptoms.

Central nervous system— The brain and spinal cord.

Spasm— Sudden, involuntary tensing of a muscle or a group of muscles.

Tranquilizer— Medicine that has a calming effect and is used to treat anxiety and mental tension.

Precautions

Prochlorperazine may cause a movement disorder called tardive dyskinesia. Signs of this disorder are involuntary twitches and muscle spasms in the face and body and jutting or rolling movements of the tongue. The condition may be permanent. Older people, especially women, are particularly at risk of developing this problem when they take prochlorperazine.

Some people feel drowsy, dizzy, lightheaded, or less alert when using this medicine. The drug may also cause blurred vision, and movement problems. For these reasons, anyone who takes this drug should not drive, use machines or do anything else that might be dangerous until they have found out how the drug affects them.

Prochlorperazine makes some people sweat less, which can allow the body to overheat. The drug may also make the skin and eyes more sensitive to the sun. People who are taking prochlorperazine should try to avoid extreme heat and exposure to the sun. When going outdoors, they should wear protective clothing, a hat, a sunscreen with a skin protection factor (SPF) of at least 15, and sunglasses that block ultraviolet (UV) light. Saunas, sunlamps, tanning booths, tanning beds, hot baths, and hot tubs should be avoided while taking this medicine. Anyone who must be exposed to extreme heat while taking the drug should check with his or her physician.

This medicine adds to the effects of alcohol and other drugs that slow down the central nervous system, such as antihistamines, cold and flu medicines, tranquilizers, sleep aids, anesthetics, some pain medicines, and muscle relaxants. Drinking alcohol while taking prochlorperazine is not advised and patients should check with the physician who prescribed the drug before combining it with any other medicines.

Do not stop taking this medicine without checking with the physician who prescribed it. Stopping the drug suddenly can cause dizziness, nausea, vomiting, tremors, and other side effects. When stopping the medicine, it may be necessary to taper down the dose gradually.

Prochlorperazine may cause false pregnancy tests.

Women who are pregnant (or planning to become pregnant) or breast feeding should check with their physicians before using antinausea medicines.

Before using prochlorperazine, people with any of the medical problems should make sure their physicians are aware of their conditions:

• Previous sensitivity or allergic reaction to prochlorperazine
• Heart disease
• Glaucoma
• Brain tumor
• Intestinal blockage
• Abnormal blood conditions, such as leukemia
• Exposure to pesticides.

Some people may experience side effects from promethazine including:

• dry mouth
• drowsiness
• confusion
• fatigue
• difficulty coordinating movements
• stuffy nose.

A physician should be contacted immediately if a patient experiences the following effects while taking promethazine:

• vision problems
• ringing in the ears
• tremors
• insomnia
• excitement
• restlessness
• yellowing of the skin or eyes
• skin rash.

Side effects

Many side effects are possible with prochlorperazine, including, but not limited to, constipation, dizziness, drowsiness, decreased sweating, dry mouth, stuffy nose, movement problems, changes in menstrual period, increased sensitivity to sun, and swelling or pain in breasts. Anyone who has unusual or troublesome symptoms after taking prochlorperazine should get in touch with his or her physician.

Side effects associated with promethazine include those listed above and interactions with various medications that may cause complications or lessen the effects of the drug. A physician should be notified of other medications the patient is on when taking promethazine.

Interactions

Prochlorperazine may interact with other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Among the drugs that may interact with prochlorperazine are antiseizure drugs such as phenytoin (Dilantin) and carbamazepine (Tegretol), anticoagulants such as warfarin (Coumadin), and drugs that slow the central nervous system such as alprazolam (Xanax), diazepam (Valium), and secobarbital (Seconal). Not every drug that interacts with prochlorperazine is listed here. A physician or pharmacist can advise patients about prescription or nonprescription (over-the-counter) drugs that might interact with Prochlorperazine.

Resources

PERIODICALS

Flake, Zachary A., Robert D. Scalley, and Austin G. Bailey. "Practical Selection of Antiemetics." American Family Physician March 1, 2004: 1169.

OTHER

"Promethazine" Medline Plus Drug Information. 〈http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a682284.html#precautions〉.

Antinausea drugs

Definition

Antinausea drugs are medicines that control nausea—a feeling of sickness or queasiness in the stomach with an urge to vomit. These drugs also prevent or stop vomiting. Drugs that control vomiting are called antiemetic drugs.

Purpose

Prochlorperazine (Compazine), the medication described in detail in this entry, controls both nausea and vomiting. Prochlorperazine is also sometimes prescribed for symptoms of mental disorders, such as schizophrenia. Prochlorperazine may be used to control the nausea and vomiting that occur during recovery from the general anesthetics used in surgery.

Some antihistamines such as dimenhydrinate (Dramamine) and meclizine (Antivert, Bonine) are useful for treatment of the nausea and vomiting associated with motion sickness.

A group of drugs called the 5HT3 inhibitors, ondansetron (Zofran) and granisetron (Kytril), are used to control the nausea and vomiting associated with anticancer drugs. Ondansetron and granisetron are also valuable for controlling nausea and vomiting following surgery.

Corticosteroid hormones such as dexamethasone (Decadron, Hexdrol) may also be used as antiemetics.

Description

Prochlorperazine is available only with a physician's prescription. It is sold in syrup, capsule, tablet, injection, and suppository forms.

Recommended dosage

To control nausea and vomiting in adults, the usual dose is:

• Tablets: one 5-mg or 10-mg tablet three to four times a day
• Extended-release capsules: one 15-mg capsule first thing in the morning or one 10-mg capsule every 12 hours
• Suppository: 25 mg, twice a day
• Syrup: 5–10 mg three to four times a day
• Injection: 5–10 mg injected into a muscle three to four times a day

Doses for children must be determined by a physician.

Precautions

Prochlorperazine may cause a movement disorder called tardive dyskinesia. Signs of this disorder are involuntary twitches and muscle spasms in the face and body and jutting or rolling movements of the tongue. The condition may be permanent. Older people, especially women, are particularly at risk of developing this problem when they take prochlorperazine.

Some people feel drowsy, dizzy, lightheaded, or less alert when using this medicine. The drug may also cause blurred vision, and movement problems. For these reasons, people who take this drug should not drive, use machines, or do anything else that might be dangerous until they have found out how the drug affects them.

Prochlorperazine makes some people sweat less, which can allow the body to overheat. The drug may also make the skin and eyes more sensitive to the sun. People who are taking prochlorperazine should try to avoid extreme heat and exposure to the sun. When going outdoors, they should wear protective clothing, a hat, a sunscreen with a skin protection factor (SPF) of at least 15, and sunglasses that block ultraviolet (UV) light. Saunas, sunlamps, tanning booths, tanning beds, hot baths, and hot tubs should be avoided while taking this medicine. Anyone who must be exposed to extreme heat while taking the drug should check with his or her physician.

This medicine adds to the effects of alcohol and other drugs that slow down the central nervous system, such as antihistamines, cold and flu medicines, tranquilizers, sleep aids, anesthetics, some pain medicines, and muscle relaxants . People taking prochlorperazine should not drink alcohol, and should check with the physician who prescribed the drug before combining it with any other medicines.

Patients should not stop taking this medicine without checking with the physician who prescribed it. Stopping the drug suddenly can dizziness, nausea, vomiting, tremors, and other side effects. When stopping the medicine, it may be necessary to taper the dose gradually.

Prochlorperazine may cause false pregnancy tests.

Women who are pregnant (or planning to become pregnant) or are breastfeeding should check with their physicians before using this medicine.

Before using prochlorperazine, people with any of these medical problems should make sure their physicians are aware of their conditions:

• previous sensitivity or allergic reaction to prochlorperazine
• heart disease
• glaucoma
• brain tumor
• intestinal blockage
• abnormal blood conditions, such as leukemia
• exposure to pesticides

Side effects

Many side effects are possible with this drug, including, but not limited to, constipation, dizziness, drowsiness, decreased sweating, dry mouth, stuffy nose, movement problems, changes in menstrual period, increased sensitivity to sun, and swelling or pain in breasts. Anyone who has unusual or troublesome symptoms after taking prochlorperazine should contact his or her physician.

Interactions

Prochlorperazine may interact with other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Among the drugs that may interact with prochlorperazine are antiseizure drugs such as phenytoin (Dilantin) and carbamazepine (Tegretol), anticoagulants such as warfarin (Coumadin), and drugs that slow the central nervous system such as alprazolam (Xanax), diazepam (Valium), and secobarbital (Seconal). Not every drug that interacts with prochlorperazine is listed here, and all patients should consult with a physician or pharmacist before taking any other prescription or nonprescription (over-the-counter) drug with prochlorperazine.

Resources

books

Brody, T. M., J. Larner, K. P. Minneman, and H. C. Neu. Human Pharmacology: Molecular to Clinical, 2nd ed. St. Louis: Mosby Year-Book, 1998.

Griffith, H. W., and S. Moore. 2001 Complete Guide to Prescription and Nonprescription Drugs. New York: Berkely Publishing Group, 2001.

other

"Anticholinergics/Antispasmodics." Medline Plus Drug Information. [cited June 25 2003] <http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202049.html>.

"Antihistamines (Systemic)." Medline Plus Drug Information. [cited June 25 2003] <http://www.nlm.nih.gov/medline plus/druginfo/uspdi/202060.html>.

"Ondansetron." Medline Plus Drug Information. [cited June 25 2003] <http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a601209.html>.

"Prochlorperazine." Medline Plus Drug Information. [cited June 25, 2003] < http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a682116.html>.

Nancy Ross-Flanigan Sam Uretsky, PharmD