Robitussin for dry coughs is a full strength cough suppressant for the relief of persistent and irritating dry and tickly coughs this formulation works by reducing the feeling of needing to cough it does this by effectively suppressing the cough centre in the brain which helps prevent the annoying symptoms during the day and contribute to a restful nights sleep robitussin dry cough medicine is a pleasant tasting syrup it is sugar free and does not cause drowsiness