Some people do not react well to codeine at all. My dentist gave me some once for a tooth infection I had bad pain with- after one dose i felt so AWFUL, like I wanted to just die! So ill, dizzy and nauseous- sick all over, shaking, terribly drugged, and my heart was racing too. I probably "should" have gone to the emergency clinic, but I didn't want to move....I curled up in bed and toughed it out until it wore off about 8 hours later, but I never ever want to take codeine again.