Promethazine is used to relieve or prevent the symptoms of hay fever, allergic conjunctivitis (inflammation of the eye), and other types of allergy or allergic reactions. It works by preventing the effects of a substance called histamine, which is produced by the body. Histamine can cause itching, sneezing, runny nose, and watery eyes. It can sometimes close up the bronchial tubes (air passages of the lungs) and make breathing difficult .
Promethazine is also used to prevent and control motion sickness, nausea, vomiting, and dizziness. In addition, it may be used to help people go to sleep and control their pain or anxiety before or after surgery or other procedures
Allergy
The normal recommended oral dose is 25 mg administered before bed; alternatively, a patient can be given 6.25 to 12.5 mg three times before meals and on retiring, as necessary.
Motion Sickness
The average recommended adult dose is 25 mg, taken twice daily. The initial dose needs to be taken one-half to one hour before travel and repeated every eight to twelve hours later if needed. On days following travel, 25 mg can be administered when up and repeated before the evening meal.
Nausea and Vomiting
Antiemetics are not recommended to treat vomiting of unknown etiology in children and adolescents. The average effective dose of promethazine for the active treatment of nausea and vomiting in children or adults is 25 mg.
To treat nausea and vomiting in children, the usual recommended dose is 0.5 mg/pound (body weight). The dose should be based on the patient's age, body weight, and the severity of nausea/vomiting.
