What is the best medication for productive cough for a patient with coronary artery disease?

Depends: on the REASON for the cough NOT if it is productive or not! Ask again with more info! Dr Z

Depends: on the etiology of the cough

Over the counter: If the cough is of short duration and there are no other symptoms you can try medicine available without prescription like Robituscin DM.But if it persists and if you are a smoker or associated with other symptoms like wheezing,fever,shortness of breath etc,then consult your MD