It is a cough suppressant and will keep you from coughing up mucus. However, you may need DM to help you sleep. Taking one dose at bedtime is ok. Hot beverages, especially those with honey, soothe the throat. Suck on cough drops, lozenges, or hard candy to soothe and moisten a dry irritated throat.
Cough drops can soothe an irritated throat, but have no effect on the coght producing mechanism.
Expensive medicine flavored cough drops are not any better than cheaper candy flavored ones or hard candy. Elevate your head at night with extra pillows.