Promethazine (brand names Phenergan, Avomine, Sominex) is an antihistamine medicine that relieves the symptoms of allergies.[1] Promethazine sometimes comes mixed with other medicines, such as paracetamol, dextromethorphan or pseudoephedrine, to treat coughs and colds or pain.[1]
It comes as tablets, capsules or as a liquid that is swallowed. It is known as a drowsy (sedating) antihistamine, so it is more likely to make people feel sleepy than other antihistamines.[1]