INTRAVENOUS ADMINISTRATION OF DRUGS Inulin and PAH will be administered through a 20G venous cannula inserted into the forearm. Inulin and PAH will be infused at a constant infusion rate throughout the 8 hour study period. Acetylcysteine/placebo will be administered through a second 20G venous cannula inserted into the same forearm. We will use the intravenous acetylcysteine preparation currently used in the Royal Infirmary of Edinburgh (Parvolex, UCB Pharma Limited). Placebo will be sodium chloride solution for infusion. Active or placebo infusions will be prepared by the Clinical Research Facility on each study day according to the randomized allocation order.