Dextromethorphan is a non-narcotic cough suppressant which acts centrally to raise the threshold for coughing. Its effectiveness in suppressing cough has been found to be about equal to codeine. Pseudoephedrine hydrochloride is used as a nasal and bronchial decongestant. It is said to have less pressor activity and CNS effects than ephedrine of which it is a stereoisomer. Promethazine hydrochloride is a H1-receptor blocking agent. In therapeutic dosages, promethazine produces no significant effects on the cardiovascular system.