What's the concern with anticholinergic medications? Many over-the-counter drugs have anticholinergic properties. Drugs with anticholinergic properties block the action of the neurotransmitter chemical, acetylcholine. Phenergan Injection (promethazine hydrochloride injection, USP), is a sterile, pyrogen-free solution for deep intramuscular or intravenous administration. Facts and Stats. According to the National Sleep Foundation’s 2005 Sleep in America poll, 60% of adult drivers – about 168 million people – say they have driven a vehicle while feeling drowsy in the past year, and more than one-third, (37% or 103 million people), have actually fallen asleep at the wheel! Codeine is used to relieve mild to moderate pain. It is also used, usually in combination with other medications, to reduce coughing. Codeine will help relieve symptoms but will not treat the cause of symptoms or speed recovery. Promethazine is used to relieve the symptoms of allergic reactions such as allergic rhinitis (runny nose and watery eyes caused by allergy to pollen, mold or dust), allergic conjunctivitis (red, watery eyes caused by allergies), allergic skin reactions, and allergic reactions to blood or plasma products. Dr Wayne Osborne discusses the supposed benefits and risks of coffee, particularly how many cups per day can be detrimental or significantly dangerous towards health, and when throughout the day is best to drink it. PHENERGAN™ (promethazine hydrochloride) Suppositories, USP. DESCRIPTION. Each rectal suppository contains 12.5 mg or 25 mg promethazine HCl with ascorbyl palmitate, colloidal silicon dioxide, white wax, hard fat, and glyceryl monostearate. Consumer information about the medication PROMETHAZINE/CODEINE SYRUP - ORAL (Phenergan w/ codeine), includes side effects, drug interactions, recommended dosages, and storage information. Read more about the prescription drug PROMETHAZINE/CODEINE SYRUP - ORAL. Promethazine is the generic form of the brand-name drug Phenergan, used as an antihistamine, sedative, and anti-nausea drug. Your doctor may also prescribe promethazine to relieve allergy symptoms. Phenergan (promethazine) belongs to a group of drugs called phenothiazines. It works by changing the actions of chemicals in your brain. Promethazine also acts as an antihistamine.