Prescription requiredAntiallergic / Antihistamine

Phenergan Syrup — Side Effects & Warnings

Known side effects of Phenergan Syrup include Drowsiness, dizziness, dry mouth, blurred vision, constipation, nausea, vomiting, confusion (especially in elderly), urinary retention. Not everyone experiences these side effects.

Medically reviewed by Dr. Balaji Krishnan, MBBS · Updated July 2026

Common Side Effects

Drowsiness
dizziness
dry mouth
blurred vision
constipation
nausea
vomiting
confusion (especially in elderly)
urinary retention

This is not an exhaustive list. Consult your doctor if you notice any unusual symptoms.

Important Warnings

Schedule H: use only on prescription. Causes significant drowsiness—avoid driving, alcohol and other sedatives. Not recommended in children below 2 years (risk of severe respiratory depression); use with caution and only under medical advice in older children. Use caution in asthma/COPD, sleep apnoea, glaucoma, prostate enlargement/urinary retention, epilepsy, and liver disease. May cause photosensitivity. Seek urgent help for breathing difficulty, severe sedation, allergic reaction, or unusual movements.

Drug Interactions

Phenergan Syrup may interact with the following:

Alcohol
opioids
benzodiazepines and other CNS depressants (increased sedation/respiratory depression); other anticholinergics (increased dry mouth/constipation/urinary retention); MAO inhibitors (enhanced anticholinergic/CNS effects); tricyclic antidepressants; antihypertensives (additive dizziness/low BP).

Always tell your doctor about all medicines you are taking, including over-the-counter drugs and supplements.

Pregnancy Safety

Use with caution / Consult doctor (especially in first trimester)

Alcohol Interaction

Avoid

Habit Forming

Storage

Store below 25°C, protected from light and moisture. Keep bottle tightly closed. Keep out of reach of children.

Phenergan Syrup — Safety Summary

Composition: Promethazine hydrochloride 5 mg/5 mL
Prescription: Required (Rx)
Pregnancy: Use with caution / Consult doctor (especially in first trimester)
Alcohol: Avoid
Habit forming: No

Phenergan Syrup — Safety FAQs

What should I do if I experience side effects?

Mild side effects often resolve on their own. If side effects are severe or persistent, stop the medicine and consult your doctor immediately.

Are all listed side effects common?

No. Some side effects are common while others are rare. Not everyone experiences side effects. Consult your doctor if you are concerned.

Can I take this medicine with other drugs?

Some medicines interact with each other. Always inform your doctor about all medicines you are currently taking.

When should I seek emergency help?

Seek immediate medical attention if you experience severe allergic reactions (difficulty breathing, swelling of face/throat), chest pain, or any life-threatening symptoms.

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Safety disclaimer

This information is for educational purposes only and is not a substitute for professional medical advice. If you experience severe side effects, seek medical attention immediately.