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Does Phenergan (promethazine) cause side effects?
Phenergan (promethazine) is an antihistamine used to prevent and treat nausea and vomiting related to certain conditions (such as before/after surgery and motion sickness). It is also used to treat allergy symptoms such as
Phenergan may be used to help you feel sleepy/relaxed before and after surgery or to help certain narcotic pain relievers (such as meperidine) work better. It may also be used for a short time to treat a runny nose due to the common cold.
Phenergan works by blocking the histamines the body makes during an allergic reaction. Its other effects (such as anti-nausea, calming, pain relief) may work by affecting other natural substances (such as acetylcholine) and by acting directly on certain parts of the brain.
Common side effects of Phenergan include
Serious side effects of Phenergan include
- slow heartbeat,
- mental/mood changes (such as hallucinations, nervousness, irritability, restlessness, confusion),
- unusual/uncontrolled movements (such as fixed upward stare, neck twisting, tongue movements),
- shaking (tremor),
- difficulty urinating,
- easy bleeding/bruising,
- signs of infection (such as fever, persistent sore throat),
- severe stomach/abdominal pain,
- persistent nausea/vomiting,
- yellowing eyes/skin (jaundice),
- seizures, and
- neuroleptic malignant syndrome (high body temperature, severe extrapyramidal symptoms, changes in consciousness and mental status, and increased heart rate with low or high blood pressure).
Drug interactions of Phenergan include
- antihistamines applied to the skin (such as diphenhydramine cream, ointment, spray) and
The risk of serious side effects (such as slow/shallow breathing, severe drowsiness/dizziness) may be increased if Phenergan is taken with other products that may also affect breathing or cause drowsiness such as
During pregnancy, Phenergan should be used only when clearly needed.
What are the important side effects of Phenergan (promethazine)?
Promethazine causes side effects such as
- confusion, and
In children less than two it can depress respiration and lead to death. Therefore, it should not be used in children less than two years old. Dizziness may also occur.
Ironically, promethazine sometimes stimulates patients, particularly children. Such stimulation may be manifest by
Other side effects include anticholinergic side effects such as:
- blurred vision,
- dry mouth,
- dilated pupils,
- urinary retention (inability to urinate),
- impotence, and
Extrapyramidal symptoms (EPS) may occur. EPS are categorized as dystonic reactions (alterations in muscle tone), sharp, involuntary muscle movements (often limited to one muscle or muscle group), akathisia (subjective restlessness), and Parkinsonism.
Parkinsonian symptoms are more common in older persons whereas children more often develop involuntary muscle movement reactions. Dystonic reactions are most commonly seen during the first week of treatment. Restlessness and Parkinsonian symptoms usually develop days to weeks after starting therapy.
A serious complex called neuroleptic malignant syndrome (NMS) can occur in patients receiving phenothiazines. NMS consists of
- high body temperature,
- severe EPS,
- changes in consciousness and mental status, and
- increased heart rate with low or high blood pressure.
NMS occurs more frequently in young men and in persons who are dehydrated.
Rarely, blood cell disorders can occur; low white cell counts can lead to infections.
Phenothiazines such as promethazine can cause skin hyperpigmentation (darkening) but usually only after prolonged use. The effect usually is restricted to areas of the body exposed to sunlight. Thus, people who need long-term treatment with promethazine should either keep out of the sun or use effective sunscreens.
Phenothiazines can cause
- blurred vision,
- difficulty with nighttime vision, or
- changes in color vision.
Phenothiazines such as promethazine block dopamine receptors. This effect can lead to increases in blood levels of prolactin, a hormone involved in lactation (formation of breast milk). As a result, phenothiazines can cause the breast to produce fluid ("milk") even when a woman is not pregnant.
Additionally, phenothiazines can cause:
Phenergan (promethazine) side effects list for healthcare professionals
Central Nervous System
Drowsiness is the most prominent CNS effect of this drug. Sedation, somnolence, blurred vision, dizziness; confusion, disorientation, and extrapyramidal symptoms such as oculogyric crisis, torticollis, and tongue protrusion; lassitude, tinnitus, incoordination, fatigue, euphoria, nervousness, diplopia, insomnia, tremors, convulsive seizures, excitation, catatonic-like states, hysteria. Hallucinations have also been reported.
Cardiovascular – Increased or decreased blood pressure, tachycardia, bradycardia, faintness.
Hematologic – Leukopenia, thrombocytopenia, thrombocytopenic purpura, agranulocytosis.
Gastrointestinal – Dry mouth, nausea, vomiting, jaundice.
Other – Angioneurotic edema. Neuroleptic malignant syndrome (potentially fatal) has also been reported.
Hyperexcitability and abnormal movements have been reported in patients following a single administration of promethazine HCl.
Consideration should be given to the discontinuation of promethazine HCl and to the use of other drugs if these reactions occur. Respiratory depression, nightmares, delirium, and agitated behavior have also been reported in some of these patients.
To report suspected adverse reactions, contact Renaissance Pharma, Inc. at 1-866-897-5002 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
What drugs interact with Phenergan (promethazine)?
CNS Depressants – Phenergan (Promethazine HCl) Suppositories may increase, prolong, or intensify the sedative action of other central-nervous-system depressants, such as
- sedatives/hypnotics (including barbiturates),
- narcotic analgesics,
- general anesthetics,
- tricyclic antidepressants, and
Therefore, such agents should be avoided or administered in reduced dosage to patients receiving promethazine HCl. When given concomitantly with Phenergan (Promethazine HCl) Suppositories, the dose of barbiturates should be reduced by at least one-half, and the dose of narcotics should be reduced by one-quarter to one-half.
Dosage must be individualized. Excessive amounts of promethazine HCl relative to a narcotic may lead to restlessness and motor hyperactivity in the patient with pain; these symptoms usually disappear with adequate control of the pain.
Epinephrine – Because of the potential for promethazine HCl to reverse epinephrine's vasopressor effect, epinephrine should NOT be used to treat hypotension associated with Promethazine HCl Suppositories overdose.
Anticholinergics – Concomitant use of other agents with anticholinergic properties should be undertaken with caution.
Monoamine Oxidase Inhibitors (MAOI) – Drug interactions, including an increased incidence of extrapyramidal effects, have been reported when some MAOI and phenothiazines are used concomitantly. This possibility should be considered with Phenergan (Promethazine HCl) Suppositories.
Drug/Laboratory Test Interactions
The following laboratory tests may be affected in patients who are receiving therapy with promethazine HCl:
Diagnostic pregnancy tests based on immunological reactions between HCG and anti-HCG may result in false-negative or false-positive interpretations.
Glucose Tolerance Test
An increase in blood glucose has been reported in patients receiving promethazine HCl.
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Related Disease Conditions
Nausea and Vomiting
Nausea is an uneasiness of the stomach that often precedes vomiting. Nausea and vomiting are not diseases, but they are symptoms of many conditions. There are numerous cases of nausea and vomiting. Some causes may not require medical treatment, for example, motion sickness, and other causes may require medical treatment by a doctor, for example, heart attack, lung infections, bronchitis, and pneumonia. Some causes of nausea and vomiting may be life-threatening, for example, heart attack, abdominal obstruction, and cancers. Treatment of nausea and vomiting depends upon the cause.
An allergy refers to a misguided reaction by our immune system in response to bodily contact with certain foreign substances. When these allergens come in contact with the body, it causes the immune system to develop an allergic reaction in people who are allergic to it. It is estimated that 50 million North Americans are affected by allergic conditions. The parts of the body that are prone to react to allergies include the eyes, nose, lungs, skin, and stomach. Common allergic disorders include hay fever, asthma, allergic eyes, allergic eczema, hives, and allergic shock.
Digestive Diseases: Nausea and Vomiting
Second Source WebMD Medical Reference
Sinus Infection vs. Allergies
Both sinus infections and allergies (allergic rhinitis) cause symptoms such as runny or stuffy nose and fatigue. Sinus infection (known as sinusitis) is inflammation of the sinuses, caused by infection from bacteria, viruses, and/or fungi (molds). Allergic rhinitis occurs when certain allergies cause nasal symptoms. When a person with allergies breathes in an allergen, such as pollen, dust, or animal dander, symptoms such as runny or stuffy nose, itching, sneezing, and fatigue occur.
COVID-19 vs. Allergies
Though there is some overlap in allergy and COVID-19 signs and symptoms there are also significant differences. Symptoms that they have in common include headache, fatigue, tiredness, shortness of breath, wheezing, and sore throat. Fever does not occur with allergies but is one of the defining symptoms of COVID-19 infections.
Drug Allergy (Medication Allergy)
Drug or medication allergies are caused when the immune system mistakenly creates an immune response to a medication. Symptoms of a drug allergic reaction include hives, rash, itchy skin or eyes, dizziness, nausea, diarrhea, fainting, and anxiety. The most common drugs that people are allergic to include penicillins and penicillin type drugs, sulfa drugs, insulin, and iodine. Treatment may involve antihistamines or corticosteroids. An EpiPen may be used for life-threatening anaphylactic symptoms.
Treatment & Diagnosis
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Medications & Supplements
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Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Professional side effects and drug interactions sections courtesy of the U.S. Food and Drug Administration.