Codeine is a pro-drug with its analgesic activity being dependent on the metabolism of codeine to morphine. The metabolism of codeine to morphine is catalyzed by the cytochrome P450 enzyme 2D6 (CYP2D6) of which there are over 70 genetic variants leading to differing metabolic capabilities within populations. It is hypothesized that the changes in PPT/PTT will vary based on the individuals ability to convert morphine to codeine.