Kim Annink

204 Chapter 9 Figure 4: Estimated AUC values of allopurinol and oxypurinol per patient. The target AUC is shown by the dotted line. One patient had a very low AUC of oxypurinol with oxypurinol concentrations that were about 10% of corresponding concentrations in the other patients. The metabolic ratio (allopurinol to oxypurinol) seemed to be lower both after the first and second dose (data not shown). Subsequently the hypoxanthine, xanthine and uric acid levels of this patient were higher compared to the other patients, suggesting less xanthine-oxidase inhibition. Figure 5 and 6 show the GOF plots for both allopurinol and oxypurinol. Figure 5: Goodness of fit plots for allopurinol