title: A Bayesian method for predicting 5-fluorouracil pharmacokinetic parameters following short-term infusion in patients with colorectal cancer.
abstract: The objective of this study was to develop a population pharmacokinetic model and validate it using a Bayesian approach for predicting, a priori and a posteriori, the individual volume of distribution (V(d)) and clearance (Cl) of 5-fluorouracil (5-FU) given as short-term intravenous infusion in weekly and multiple doses. Forty-four patients were divided in group A (5-FU weekly doses) including 27 patients with nonmetastatic colorectal adenocarcinoma treated with 450 mg/m(2) of 5-FU, 1 day per week for 48 doses, plus oral levamisol (50 mg/8 h) for 3 days, every 15 days and group B (5-FU multiple doses) including 17 patients with metastatic colorectal adenocarcinoma, receiving 5-FU (425 mg/m(2)) plus intravenous folinic acid (20 mg/m(2)) over 5 consecutive days, every 4 weeks for six cycles. In both groups 5-FU was administered as a 30-60-min infusion. A total of 176 plasma concentrations were analyzed using a NONMEM program according to a linear one-compartment model. In group A, 5-FU population pharmacokinetic parameters were obtained and the covariables studied were age, gender, weight, ideal body weight, height, body surface area, creatinine clearance, and hepatic function tests. A priori and a posteriori validation of this model was carried out with plasma concentrations obtained in day 1 in group B. In group B, population pharmacokinetic parameters of 5-FU following multiple doses were estimated using scale factors to identify differences in 5-FU V(d) and Cl between days 1 and 4, and the interindividual, interoccasion, and residual variabilities studied. V(d) was 0.266 L/kg of ideal body weight and Cl was 1.21 L/h. kg of total weight following weekly doses. The plasma sample obtained at 10 min gave the best accuracy and precision predictions. When 5-FU was administered in multiple doses, the Cl of the drug in day 4 is reduced by 30.14% compared to day 1. The interoccasion variability was lower than interindividual variability for both V(d) and Cl, suggesting that it could be feasible to individualise dosage of 5-FU for subsequent cycles from data obtained in a previous one in an attempt to improve the therapeutic index of colorectal cancer treatment.
authors.affiliation: Pharmacy Service, Hospital Universitario Dr Peset Avda Gaspar Aguilar, 90 Valencia 46017 Spain. climente_mon@gva.es
authors.forename: M
authors.initials: M
authors.lastname: Climente-Martí
authors.forename: M
authors.initials: M
authors.lastname: Merino-Sanjuán
authors.forename: D
authors.initials: D
authors.lastname: Almenar-Cubells
authors.forename: N V
authors.initials: NV
authors.lastname: Jiménez-Torres
mesh_terms: D000328:Adult; D000368:Aged; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D001499:Bayes Theorem; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D004334:Drug Administration Schedule; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D008954:Models, Biological
chemical_list: D000964:Antimetabolites, Antineoplastic; D005472:Fluorouracil