Dear Sir. Concerning your issue about the drug glucuronidation rate over time . The recognition of glucuronidation as an important metabolic pathway has lent increasing efforts towards better understanding of the molecular mechanisms of UGT functions and of the substrate structural features associated with UGT selectivity. Inevitably, a molecular-level structural elucidation of the protein is necessary for such pursuits. Here, a homology model of UGT1A9 was constructed aiming to enhance our understanding of interactions between UGT1A9 and substrates, in addition to the CoMFA/CoMSIA results. Glucuronidation is a major metabolic pathway for a large number of drugs in humans. Conjugation of drugs and other chemicals with glucuronic acid is catalyzed by the multigene UDP-glucuronosyltransferase family. It is believed that a number (unspecified at present) of glucuronosyltransferase isozymes, which probably differ in terms of substrate specificity and regulation, contribute to drug glucuronidation. Factors known to influence the pharmacokinetics of glucuronidated drugs in man, presumably via an effect on specific glucuronosyltransferases, include age (especially the neonatal period), cigarette smoking, diet, certain disease states, coadministered drugs, ethnicity, genetics and hormonal effects. I think the following below links may help you in your analysis: