PM is used for the treatment of allergic symptoms, often given at night because of its marked sedative effects. Drug hypersensitivity reactions and allergic conditions have also been treated with promethazine especially in emergencies. It can also be used in treating symptoms of asthma, pneumonia, or other lower respiratory tract infections; in fact, inhalation therapy for relieving bronchial spasm is made by quaternary salts of promethazine. PM is sometimes used for its sedative effects and in some countries is marketed for this purpose, including the sedation of young children as nasal sleep introducing drug, or it can be used as an anaesthetic premedication to produce sedation, reduce anxiety, or to reduce postoperative nausea and vomiting as dose-controlled transdermal device. The drug is often given in conjunction with an opiate analgesic such as pethidine, particularly in obstetrics. Taken before travelling, promethazine is effective in preventing motion sickness. Vomiting from other causes can be treated with higher or more frequent doses.