Side Effects of Phenergan (promethazine)

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 rash, itching, and runny nose. Phenergan may be used to help you feel sleepy/relaxed before and after surgery or to help certain narcotic pain relievers 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 histamines the body makes during an allergic reaction. Its other effects such as anti-nausea, calming, and pain relief may work by affecting other natural substances and by acting directly on certain parts of the brain.

Common side effects of Phenergan include fainting, slow heartbeat, mental/mood changes, unusual/uncontrolled movements, shaking, difficulty urinating, easy bleeding/bruising, signs of infection, severe stomach/abdominal pain, persistent nausea/vomiting, yellowing eyes/skin, seizures, and neuroleptic malignant syndrome.

The risk of serious side effects may be increased if Phenergan is taken with other products that may also affect breathing or cause drowsiness such as alcohol, drugs for sleep or anxiety, muscle relaxants, and narcotic pain relievers.

During pregnancy, Phenergan should be used only when clearly needed. It is unknown if Phenergan passes into breast milk. It may have undesirable effects on a nursing infant.

What are the important side effects of Phenergan (promethazine)?

Promethazine causes side effects such as sedation, confusion, and disorientation. In children less than two, it can depress respiration and lead to death. Dizziness may also occur.

Ironically, promethazine sometimes stimulates patients, particularly children, manifesting as restlessness, inability to sleep, heart palpitations, or seizures.

Other side effects include blurred vision, dry mouth, dilated pupils, nausea, urinary retention, impotence, constipation, and extrapyramidal symptoms such as dystonic reactions, sharp involuntary muscle movements, akathisia, and Parkinsonism.

A serious complex called neuroleptic malignant syndrome (NMS) can occur in patients receiving phenothiazines, consisting of high body temperature, severe extrapyramidal symptoms, 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, and low white cell counts can lead to infections.

Phenothiazines such as promethazine can cause skin hyperpigmentation, but usually only after prolonged use. Phenothiazines can also cause blurred vision, difficulty with nighttime vision, changes in color vision, liver damage, jaundice, and hormonal changes resulting in missed menstrual periods, breast enlargement or tenderness, loss of sexual drive, impotence, inability to ejaculate, priapism, and weight gain.

Phenergan (promethazine) side effects list for healthcare professionals

Central Nervous System

Drowsiness is the most prominent CNS effect of this drug, along with sedation, blurred vision, dizziness, confusion, disorientation, extrapyramidal symptoms, lassitude, tinnitus, incoordination, fatigue, euphoria, nervousness, diplopia, insomnia, tremors, convulsive seizures, excitation, catatonic-like states, hysteria, and hallucinations.

Cardiovascular – Increased or decreased blood pressure, tachycardia, bradycardia, faintness.

Hematologic – Leukopenia, thrombocytopenia, thrombocytopenic purpura, agranulocytosis.

Gastrointestinal – Dry mouth, nausea, vomiting, jaundice.

Respiratory – Asthma, nasal stuffiness, respiratory depression, and apnea.

Other – Angioneurotic edema. Neuroleptic malignant syndrome potentially fatal).

Paradoxical Reactions

Hyperexcitability and abnormal movements have been reported in patients following a single administration of promethazine HCl. Consideration should be given to discontinuing promethazine HCl and using 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 visit 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 alcohol, sedatives/hypnotics, narcotics, narcotic analgesics, general anesthetics, tricyclic antidepressants, and tranquilizers. 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:

Pregnancy Tests

Diagnostic pregnancy tests 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.

Summary

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 rash, itching, and runny nose. Common side effects of Phenergan include drowsiness, dizziness, constipation, blurred vision, and dry mouth. During pregnancy, Phenergan should be used only when clearly needed. It is unknown if Phenergan passes into breast milk.