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What Is Phenergan?

Phenergan is a brand name for promethazine hydrochloride, a first-generation antihistamine with sedating and antiemetic effects. It is used for selected allergic conditions, prevention or control of nausea and vomiting, motion sickness, and sedation in certain medical settings. Promethazine is available in oral formulations, suppositories, and injectable products, with instructions that differ by formulation. Phenergan is not appropriate for children younger than two years because it can cause fatal respiratory depression. Patients should also be aware of its strong sedating and anticholinergic effects.

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What Is Phenergan?

Phenergan is a brand name for promethazine hydrochloride, a first-generation antihistamine with sedating and antiemetic effects. It is used for selected allergic conditions, prevention or control of nausea and vomiting, motion sickness, and sedation in certain medical settings. Promethazine is available in oral formulations, suppositories, and injectable products, with instructions that differ by formulation. Phenergan is not appropriate for children younger than two years because it can cause fatal respiratory depression. Patients should also be aware of its strong sedating and anticholinergic effects.

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How Does Phenergan Work?

Phenergan blocks histamine H1 receptors, reducing symptoms associated with allergic reactions, including itching, sneezing, and a runny nose. Promethazine also acts on pathways involved in nausea, vomiting, and motion sickness. Its activity in the central nervous system contributes to sedation, while anticholinergic effects can produce dry mouth, blurred vision, and constipation. Promethazine does not treat the underlying cause of every gastrointestinal symptom. Combining it with opioids, alcohol, or other sedatives can substantially increase the risk of breathing suppression.

What Conditions Does Phenergan Treat?

Promethazine is indicated for selected allergic conditions, including allergic rhinitis, allergic conjunctivitis, and certain skin reactions. It is also used to prevent or control motion sickness, nausea, and vomiting associated with some medical or surgical situations, and for sedation before or after certain procedures. Some formulations are used alongside other medications in anesthesia-related care. Phenergan is not intended to treat lower respiratory tract symptoms such as asthma. Use in children aged two years and older requires caution, and uncomplicated pediatric vomiting generally should not be treated routinely with promethazine.

How Should Phenergan Be Taken?

Phenergan dosing depends on the formulation, patient age, and reason for treatment. Adults taking oral promethazine for motion sickness may receive 25 mg before travel, with additional doses only according to the product instructions. Allergy and nausea regimens can involve different doses and intervals. Oral tablets and liquid should be measured or taken exactly as prescribed. Promethazine must not be given to children younger than two years. Injectable formulations require specialized administration precautions because accidental injection into an artery or surrounding tissue can cause serious injury. Patients should avoid alcohol and driving when sedated.

What Are the Side Effects and Warnings of Phenergan?

Common side effects include significant drowsiness, dizziness, dry mouth, blurred vision, and constipation. Promethazine carries a boxed warning for potentially fatal respiratory depression in children younger than two years. Use in older children also requires caution. Serious adverse effects include severe sedation, seizures, abnormal movements, and neuroleptic malignant syndrome. Injectable promethazine carries additional warnings for severe tissue injury, including gangrene, from improper administration. Alcohol, opioids, and other sedatives can increase breathing and consciousness-related risks. Patients should seek emergency care for slowed breathing, severe confusion, or unresponsiveness.

Common Questions About Phenergan

Is Phenergan the same as promethazine?

Yes. Phenergan is a brand name for promethazine, a sedating first-generation antihistamine with anti-nausea effects.

Can Phenergan prevent motion sickness?

Yes. Promethazine can prevent or control motion sickness when taken according to the prescribed or labeled schedule.

Can children younger than two years take Phenergan?

No. Promethazine is contraindicated in children younger than two years because of the risk of fatal respiratory depression.

Can Phenergan cause dry eyes or blurred vision?

Yes. Promethazine has anticholinergic properties that can contribute to visual blurring and dryness. Contact lens wearers with persistent discomfort should seek advice from an eye care professional.

References

DailyMed - PHENERGAN (promethazine hydrochloride) tablet. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=eec705f7-123a-7926-e053-2a95a90af46d. Date Accessed October 30, 2026.

Promethazine. LiverTox. https://www.ncbi.nlm.nih.gov/books/NBK548427/. Date Accessed October 30, 2026.

Promethazine. MedlinePlus. https://medlineplus.gov/druginfo/meds/a682284.html. Date Accessed October 30, 2026.

Promethazine. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/promethazine. Date Accessed October 30, 2026.

Promethazine. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK544361/. Date Accessed October 30, 2026.