cough medicines that are expectorants are fine as they thin the mucous. The onces that have a cough suppresant are not recommended. When possible don't buy drugs that treat more than one thing. Don't take combo drugs if at all possible.
I also heard to stay away from cough medicine if you have emphysema.
What drugs are you referring to? You would not want anything that dries out the lungs and you certainly don't want any inhalers that you can buy OTC but the mucous thinners are OK. Nothing else really would be good for you.