Antipyrine kinetics in liver disease and liver transplantation

Antipyrine kinetics were studied in seven normal subjects, 10 patients with liver disease, and 13 clinically stable patients who received a liver transplant. Five patients were studied both before and after liver transplantation. Antipyrine concentrations in saliva after oral dosing were measured by HPLC. The antipyrine t(1/2) was significantly longer (P < 0.05) in patients with liver disease than in patients undergoing liver transplantation and normal subjects. Antipyrine clearance was not significantly different between patients undergoing liver transplantation and normal subjects, but it was significantly reduced (P < 0.05) in patients with liver disease. In five patients who were studied before and after liver transplantation, there was a significant (P < 0.05) increase in the antipyrine clearance and a marked reduction in its t(1/2) after liver transplantation. These results indicate that liver transplantation improves the drug metabolizing ability of patients with liver disease and that the oxidative metabolizing capacity of the liver in clinically stable patients after liver transplantation is similar to that of normal subjects

Biopharmaceutics Classification System: The Scientific Basis for Biowaiver Extensions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41492/1/11095_2004_Article_375175.pd

Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Proguanil Hydrochloride.

Literature data relevant to the decision to waive in vivo bioequivalence testing for the approval of generic immediate release solid oral dosage forms of proguanil hydrochloride are reviewed. To clarify the Biopharmaceutics Classification System (BCS) classification, experimental solubility and dissolution studies were also carried out. The antimalarial proguanil hydrochloride, effective via the parent compound proguanil and the metabolite cycloguanil, is not considered to be a narrow therapeutic index drug. Proguanil hydrochloride salt was shown to be highly soluble according to the FDA, WHO and EMA guidelines, but data for permeability are inconclusive. Therefore, proguanil hydrochloride is conservatively classified as a BCS Class 3 substance. In view of this information and the assessment of risks associated with a false positive decision, a BCS-based biowaiver approval procedure can be recommended for orally administered solid IR products containing proguanil hydrochloride, provided well-known excipients are used in usual amounts and provided the in vitro dissolution of the test and reference products is very rapid (85% or more are dissolved in 15 minutes at pH 1.2, 4.5 and 6.8) and is performed according to the current requirements for BCS-based biowaivers

Biowaiver Monographs for Immediate-Release Solid Oral Dosage Forms: Folic Acid.

This work presents a review of literature and experimental data relevant to the possibility of waiving pharmacokinetic bioequivalence studies in human volunteers for approval of immediate-release solid oral pharmaceutical forms containing folic acid as the single active pharmaceutical ingredient. For dosage forms containing 5 mg folic acid, the highest dose strength on the World Health Organization Essential Medicines List, the dose/solubility ratio calculated from solubility studies was higher than 250 mL, corresponding to a classification as "not highly soluble." Small, physiological doses of folic acid (≤320 μg) seem to be absorbed completely via active transport, but permeability data for higher doses of 1-5 mg are inconclusive. Following a conservative approach, folic acid is classified as a Biopharmaceutics Classification System class IV compound until more reliable data become available. Commensurate with its solubility characteristics, the results of dissolution studies indicated that none of the folic acid products evaluated showed rapid dissolution in media at pH 1.2 or 4.5. Therefore, according to the current criteria of the Biopharmaceutics Classification System, the biowaiver approval procedure cannot be recommended for immediate-release solid oral dosage forms containing folic acid

Impact of pharmacometrics on drug approval and labeling decisions: A survey of 42 new drug applications

The value of quantitative thinking in drug development and regulatory review is increasingly being appreciated. Modeling and simulation of data pertaining to pharmacokinetic, pharmacodynamic, and disease progression is often referred to as the pharmacometrics analyses. The objective of the current report is to assess the role of pharmacometrics at the US Food and Drug Administration (FDA) in making drug approval and labeling decisions. The New Drug Applications (NDAs) submitted between 2000 and 2004 to the Cardio-renal, Oncology, and Neuropharmacology drug products divisions were surveyed. For those NDA reviews that included a pharmacometrics consultation, the clinical pharmacology scientists ranked the impact on the regulatory decision(s). Of about a total of 244 NDAs, 42 included a pharmacometrics component. Review of NDAs involved independent, quantitative evaluation by FDA pharmacometricians, even when such analysis was not conducted by the sponsor. Pharmacometric analyses were pivotal in regulatory decision making in more than half of the 42 NDAs. Of the 14 reviews that were pivotal to approval related decisions, 5 identified the need for additional trials, whereas 6 reduced the burden of conducting additional trials. Collaboration among the FDA clinical pharmacology, medical, and statistical reviewers and effective communication with the sponsors was critical for the impact to occur. The survey and the case studies emphasize the need for early interaction between the FDA and sponsors to plan the development more efficiently by appreciating the regulatory expectations better