Anticholinergic and antispasmodic drugs include a broad class of medications that are used to treat various medical conditions that involve contraction and relaxation of muscles. Brand Names: Pentazine, Phenergan, Promacot Generic Name: promethazine (oral) What is promethazine (Pentazine, Phenergan, Promacot)? What are the possible side effects of promethazine (Pentazine, Phenergan, Promacot)? Promethazine is a first-generation antihistamine. It is used to treat allergies, trouble sleeping, and nausea. It may help with some symptoms associated with the common cold. It may also be used for sedating people who are agitated or anxious. 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 prevent and treat nausea and vomiting related to certain conditions (such as motion sickness, or before/after surgery). It is also used to treat allergy symptoms such as rash, itching, and runny nose. What other drugs will affect Phenergan? Cold or allergy medicine, sedatives, narcotic pain medicine, sleeping pills, muscle relaxers, and medicine for seizures, depression or anxiety can interact with Phenergan and cause medical problems or increase side effects. Phenergan Images. What does Phenergan look like? Note: Multiple pictures are displayed for those medicines available in different strengths, marketed under different brand names and for medicines manufactured by different pharmaceutical companies. Viagra comes as a tablet containing sildenafil citrate, to take by mouth. For most men, the recommended dose is 50 mg. taken, as needed, approximately 1 hour before sexual activity. Promethazine is an antihistamine medicine that relieves the symptoms of allergies. It's known as a drowsy (sedating) antihistamine. It's more likely to make you feel sleepy than other antihistamines. 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.