Chlorpheniramine and dextromethorphan is a combination medicine used to treat sneezing, runny nose, and cough caused by the common cold. It is worth noting that Chlorpheniramine is an antihistamine, whereas Dextromethorphan is a cough suppressant. What Chlorpheniramine does is reduce the effects of natural chemical histamine in the body. As for Dextromethorphan, it affects the signals in the brain that trigger cough reflex. Before using this combination medicine, you need to ask your doctor if it is safe to use if you have glaucoma, an enlarged prostate, urination problems, or in case you have a cough with mucus. As far as the side effects of Chlorpheniramine/ dextromethorphan are concerned, they include dizziness, dry mouth, nose, or throat, constipation, blurred vision, or feeling restless. In order to make sure that this medicine will be safe for you and your baby during pregnancy and also during breastfeeding, you should ask your doctor before using it.