Mucinex DM has an average rating of 4.9 out of 10 from a total of 20 ratings on Drugs.com. 33% of reviewers reported a positive effect, while 50% reported a negative effect. Robitussin Cough + Chest Congestion DM has an average rating of 9.0 out of 10 from a total of 4 ratings on Drugs.com.