title: Route-dependent nonlinear pharmacokinetics of a novel HIV protease inhibitor: involvement of enzyme inactivation.
abstract: L-754,394, a furanopyridine derivative, is an experimental HIV protease inhibitor. Previous studies from this laboratory have demonstrated that L-754,394 is cleared very rapidly in animals, and that this drug is a potent mechanism-based inactivator (suicide inhibitor) for CYP3A4 in human liver microsomes. Because L-754,394 is a high-clearance drug and an enzyme inactivator, it is expected that this drug will be subject to significant first-pass metabolism, and that the degree of enzyme inactivation will be dependent not only on the dose, but also on the route of administration. The purpose of this study is to examine the effects of dose and route of administration on the kinetics of L-754,394 using rats and dogs as animal models. In both rats and dogs, L-754,394 exhibited marked dose-dependent pharmacokinetics after i.v. and oral administration. Irrespective of i.v. or oral administration, the area under the plasma concentration-time curve from zero to infinity increased with dose in a greater than proportional manner. However, the magnitude of area under the plasma concentration-time curve from zero to infinity increase was much greater after oral dosing than after i.v. administration, indicating route-dependent pharmacokinetics. Data from in vitro and in vivo studies suggested that the dose- and route-dependent pharmacokinetics were due mainly to the inactivation (destruction) of the enzymes responsible for its own metabolism.
authors.affiliation: Drug Metabolism, Merck Research Laboratories, West Point, Pennsylvania 19486, USA. jiunn_lin@merck.com
authors.forename: J H
authors.initials: JH
authors.lastname: Lin
authors.forename: I W
authors.initials: IW
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Chiba
authors.forename: J A
authors.initials: JA
authors.lastname: Nishime
authors.forename: F A
authors.initials: FA
authors.lastname: Deluna
mesh_terms: D000284:Administration, Oral; D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D019540:Area Under Curve; D001189:Aryl Hydrocarbon Hydroxylases; D002851:Chromatography, High Pressure Liquid; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D017320:HIV Protease Inhibitors / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D066298:In Vitro Techniques; D007189:Indans / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D007275:Injections, Intravenous; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D017711:Nonlinear Dynamics; D010477:Perfusion; D010879:Piperazines / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D013739:Testosterone / Q000097:blood
chemical_list: D019138:Antibodies, Blocking; D065607:Cytochrome P-450 Enzyme Inhibitors; D017320:HIV Protease Inhibitors; D007189:Indans; C094644:L 754394; D010879:Piperazines; D013739:Testosterone; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C022657:steroid hormone 6-beta-hydroxylase; C022724:testosterone 7-alpha-hydroxylase, hamster