Robitussin Ac (Guaifenesin and Codeine) may treat, side effects, dosage, drug interactions, warnings, patient labeling, reviews, and related medications including drug comparison and health resources. Compare prices and print coupons for Robitussin AC and other drugs at CVS, Walgreens, and other pharmacies. Prices start at $9.81. Overview: Codeine/guaifenesin is a combination medicine used to reduce coughing and loosen mucus from the common cold or allergies. It works by affecting the part of the brain that controls the. Robitussin AC (generic codeine 10 mg and guaifenesin) is a prescription cough medicine that combines an opioid cough suppressant with an expectorant to relieve coughs and clear mucus from your airways. Robitussin AC (generic codeine 10 mg and guaifenesin) is a prescription cough medicine that combines an opioid cough suppressant with an expectorant to relieve coughs and clear mucus from your airways. Learn about the side effects of Robitussin-AC (codeine/guaifenesin), from common to rare, for consumers and healthcare professionals. Codeine/guaifenesin is a cough syrup that contains an expectorant and an opioid. It's used to help loosen mucus and calm coughs in adults and older children. Codeine/guaifenesin is taken by mouth, typically every 4 hours as needed. Robitussin (guaifenesin) is an expectorant. It helps loosen congestion in your chest and throat, making it easier to cough out through your mouth. Robitussin is used to reduce chest congestion caused by the common cold, infections, or allergies. Medical information for Robitussin AC including its dosage, uses, side, effects, interactions, pictures and warnings. For over 70 years, Robitussin medicine and cough syrup have been the go-to choice treatment to help target cough symptoms and associated discomfort, including chest congestion, runny nose, fever, body aches and sore throat.