Actually if it's codeine/guaf that isn't "the Purple Drink". His cough syrup has guaifenesin ( robitussin) and codeine in it. The codeine will be sedating to most people. The Purple Drink is promethazine/codeine combination. The promethazine is phenergan which is very sedating itself. I don't Rx that combination personally because of its abuse potential. I'm not sure of the attraction to being drowsy but some people will do anything for a buzz.