Codeine is available in cough syrups, the most common of which is Robitussin. This decongestant was originally available over the counter, but has recently become abused as a recreational drug and is now online available by prescription. Codeine works by sending messages to the brain to relax the cough reflex to reduce dry coughing.

Other active ingredients in the syrup include Pheniramine, and Guaifenesin. Pheniramine is an antihistamine which helps to reduce cold symptoms like runny nose and sneezing. Guaifenesin helps to loosen mucus so that it can be easily coughed up. The combination of the three ingredients creates a medication that works efficiently to alleviate cold and flu symptoms.