Antiemetics Health Article

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.

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.