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Phenadoz Side Effects

Generic name: promethazine

Medically reviewed by Last updated on May 8, 2024.

Note: This document contains side effect information about promethazine. Some dosage forms listed on this page may not apply to the brand name Phenadoz.

Applies to promethazine: oral syrup, oral tablet. Other dosage forms:


Oral route (Tablet; Syrup; Solution)

Promethazine hydrochloride should not be used in pediatric patients less than 2 years of age because of the potential for fatal respiratory depression. Postmarketing cases of respiratory depression, including fatalities, have been reported with use of promethazine in pediatric patients less than 2 years of age. A wide range of weight-based doses of promethazine have resulted in respiratory depression in these patients. Caution should be exercised when administering promethazine to pediatric patients 2 years or age and older. It is recommended that the lowest effective dose of promethazine be used in pediatric patients 2 years of age and older and concomitant administration of other drugs with respiratory depressant effects be avoided.

Serious side effects of Phenadoz

Along with its needed effects, promethazine (the active ingredient contained in Phenadoz) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Stop taking promethazine and get emergency help immediately if any of the following effects occur:


- Symptoms of neuroleptic malignant syndrome; two or more occur together; most of these effects do not require emergency medical attention if they occur alone

Check with your doctor immediately if any of the following side effects occur while taking promethazine:

Incidence not known

Symptoms of overdose

Other side effects of Phenadoz

Some side effects of promethazine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Incidence not known

For Healthcare Professionals

Applies to promethazine: compounding powder, injectable solution, oral syrup, oral tablet, rectal suppository.


The most commonly reported side effect include drowsiness, dizziness, and restlessness.[Ref]

Nervous system

Frequency not reported: Drowsiness, sedation, somnolence, dizziness, extrapyramidal symptoms, incoordination, tremors, convulsive seizures, faintness, headache, neuroleptic malignant syndrome/fatal neuroleptic malignant syndrome, psychomotor impairment, antimuscarinic effects, abnormal movements, central nervous system depression, activation of epileptogenic foci, tardive dyskinesia, tic-like movements of the head and face[Ref]


Frequency not reported: Severe chemical irritation, tissue damage, burning, pain, erythema, swelling, sensory loss, palsies, paralysis, severe spasm of distal vessels, thrombophlebitis, venous thrombosis, phlebitis, abscesses, tissue necrosis, gangrene[Ref]


Frequency not reported: Restlessness, anxiety, confusion, disorientation, euphoria, nervousness, insomnia, catatonic-like states, irritability, hysteria, hallucinations, hyperexcitability, nightmares, delirium, agitation/agitated behavior[Ref]


Frequency not reported: Dry mouth, nausea, vomiting, constipation, diarrhea, tongue protrusion, gastric irritation, epigastric distress[Ref]


Frequency not reported: Bradycardia, tachycardia, palpitations, hypotension, arrhythmias, circulatory collapse, increased or decreased blood pressure[Ref]


Frequency not reported: Leukopenia, thrombocytopenia, thrombocytopenic purpura, agranulocytosis, blood dyscrasias, hemolytic anemia, aplastic anemia[Ref]


Frequency not reported: Dermatitis, photosensitivity, urticaria, rash, pruritus, angioneurotic edema, topical contact dermatitis[Ref]


Frequency not reported: Lassitude, tinnitus, fatigue, tiredness, paradoxical reactions, decreased performance (impaired driving/poor work performance, incoordination, reduced motor skills, impaired information processing)[Ref]


Frequency not reported: Asthma, nasal stuffiness, respiratory depression/fatal respiratory depression, apnea/fatal apnea, marked irregular respiration[Ref]


Frequency not reported: Blurred vision, oculogyric crisis, diplopia, angle closure glaucoma[Ref]


Frequency not reported: Anaphylaxis, angioedema, hypersensitivity reactions[Ref]


Frequency not reported: Torticollis, muscle spasms, muscle dyskinesia[Ref]


Frequency not reported: Anorexia, loss of appetite, appetite stimulation[Ref]


Frequency not reported: Jaundice, obstructive jaundice[Ref]


Frequency not reported: Urinary retention and hesitancy[Ref]

Frequently asked questions


1. (2001) "Product Information. Phenergan (promethazine)." Wyeth-Ayerst Laboratories

2. (2004) "Product Information. Promethazine Hydrochloride (promethazine)." ESI Lederle Generics

3. Cerner Multum, Inc. "UK Summary of Product Characteristics."

4. Cerner Multum, Inc. "Australian Product Information."

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.