Comparison of two different doses of paracetamol for post-operative pain relief

Paracetamol is commonly used to reduce pain after operations. Recently anaesthetists have been using bigger doses of paracetamol because it has been suggested that bigger doses will work better. However these bigger doses have never been assessed scientifically in adult patients to see if they work better, and it has not been determined at which dose the maximum effect in reducing pain occurs. We will investigate whether a 90 mg per kg body weight dose works better than a 60 mg per kilogram dose, in reducing pain after wisdom tooth extraction. We will also examine the pharmacokinetics (the way the body removes the drug) of paracetamol, and whether paracetamol changes the way blood clots at these doses. We will also examine whether these doses are safe, by monitoring liver enzymes, and making sure the blood level of paracetamol is not greater than that previously recognised to cause liver disease. The patients will be healthy volunteers scheduled to have wisdom tooth extraction. They will have blood taken at intervals for four hours after having the paracetamol. They will fill in pain scores at the same times they have blood taken.