Regular cough syrup sold in pharmacy, have a lot of side effect and there effectiveness, are not proven. Here is what my pharmacist suggested for congested lung and cough instead of buying the expectorant syrup:
A cup of hot water with honey and lemon.
I would also suggest the hot beverages of rosemary, thym and fresh ginger that I discuss in an earlier post.
Related article: Hot natural drink for cold and flu season