Benylin With Codeine Cough Syrup 100mlBenylin with Codeine is a medicine which is used to help relieve coughing and related congestion symptoms in adults. The liquid contains diphenhydramine (an antihistamine) that helps relieve coughing and dry secretions in the nose and levomenthol which helps you breathe more easily by relieving congestion. It also contains ammonium chloride (an expectorant) that helps loosen mucus so you can cough it up, and codeine (a cough suppressant). Dosage