Promethazine Uses

Promethazine is a prescription medicine that is used to treat allergic rhinitis and allergic conjunctivitis. It is also used to treat allergic reactions, including allergic reactions to blood and plasma products. Along with other drugs, promethazine is used to treat anaphylaxis (severe allergic reaction). Promethazine is also used to treat motion sickness as well as nausea and vomiting associated with pregnancy, surgery, or chemotherapy.

There may be other uses of promethazine HCl —your pharmacist or healthcare provider can give you further drug information.

Promethazine Mechanism of Action

Promethazine works by blocking a certain natural substance called histamine to treat allergies. It also blocks other natural substances to provide sedation and treat nausea and vomiting. 

Promethazine Doses

Promethazine is available as a 12.5 mg, 25 mg, and 50 mg tablet. 

Allergies

The usual dose of promethazine for allergies is 25 mg per day by mouth or rectally. It can be taken as a single 25-mg promethazine hydrochloride tablet at bedtime or as 12.5 mg before meals and at bedtime. It can also be taken in the dosage range of 6.25 to 12.5 mg three times a day orally or rectally. For severe allergic reaction, intramuscular promethazine 25 mg is given and the dose may be repeated after 2 hours if needed.

Motion Sickness

The average dose of promethazine for motion sickness in adults is 25 mg twice a day. The initial dose should be taken 30-60 minutes before anticipated travel and repeated 8-12 hours later. On subsequent travel days, promethazine 25 mg can be taken twice a day, first thing in the morning and after the evening meal.

Nausea and Vomiting

The usual dose is promethazine 25 mg orally or rectally to control nausea and vomiting. If needed, doses of 12.5 mg to 25 mg can be repeated at 4-6 hour intervals.

Sedation and Anesthesia

The usual dose of promethazine for sedation and anesthesia is 25 mg to 50 mg by mouth, rectally, or injected into a muscle.