The cough is productive with the presence of sputum which is yellowish. This represents that there is an infective pathology for which you need suitable antibiotics. Also, you require broncholytic drugs which make the sputum thin and watery so that it may come out easily. Promethazine is helpful in dry non productive cough and it is used to suppress the cough. It can be harmful in productive cough with sputum because the infective sputum will not come out on its own once the cough is suppressed.