piperidines and dihydrocodeine

Conventional mammillary models are frequently used for pharmacokinetic (PK) analysis when only blood or plasma data are available. Such models depend on the quality of the drug disposition data and have vague biological features. An alternative minimal-physiologically-based PK (minimal-PBPK) modeling approach is proposed which inherits and lumps major physiologic attributes from whole-body PBPK models. The body and model are represented as actual blood and tissue (usually total body weight) volumes, fractions (f ( d )) of cardiac output with Fick's Law of Perfusion, tissue/blood partitioning (K ( p )), and systemic or intrinsic clearance. Analyzing only blood or plasma concentrations versus time, the minimal-PBPK models parsimoniously generate physiologically-relevant PK parameters which are more easily interpreted than those from mammillary models. The minimal-PBPK models were applied to four types of therapeutic agents and conditions. The models well captured the human PK profiles of 22 selected beta-lactam antibiotics allowing comparison of fitted and calculated K ( p ) values. Adding a classical hepatic compartment with hepatic blood flow allowed joint fitting of oral and intravenous (IV) data for four hepatic elimination drugs (dihydrocodeine, verapamil, repaglinide, midazolam) providing separate estimates of hepatic intrinsic clearance, non-hepatic clearance, and pre-hepatic bioavailability. The basic model was integrated with allometric scaling principles to simultaneously describe moxifloxacin PK in five species with common K ( p ) and f ( d ) values. A basic model assigning clearance to the tissue compartment well characterized plasma concentrations of six monoclonal antibodies in human subjects, providing good concordance of predictions with expected tissue kinetics. The proposed minimal-PBPK modeling approach offers an alternative and more rational basis for assessing PK than compartmental models.

Topics: Anti-Bacterial Agents; Antibodies, Monoclonal; beta-Lactams; Biological Availability; Carbamates; Codeine; Humans; Kinetics; Liver; Midazolam; Models, Biological; Piperidines; Regional Blood Flow; Verapamil

Little information is available about the interaction between dihydrocodeine and second-generation antihistamine drugs such as cetirizine and ebastine, with particular reference to the rewarding effect of dihydrocodeine.. The effects of second generation histamine H(1) antagonists, such as cetirizine and ebastine on the antitussive and rewarding effect of dihydrocodeine were examined in mice.. Mice were exposed to a nebulized solution of capsaicin (30 micromol/l) under conscious and identical conditions, using a body plethysmograph. The coughs produced during a 3-min exposure period were counted. Effects of H(1) antagonists on the reinforcing effect of dihydrocodeine were assessed by using the conditioned place preference procedure in mice.. The antitussive effect of dihydrocodeine was enhanced by the simultaneous administration of either cetirizine or ebastine. There was no statistical difference between the ED(50) of dihydrocodeine in combination with ebastine and that of dihydrocodeine in combination with cetirizine. Concurrent dosing of dihydrocodeine and ebastine produced a significant place preference. This behavioral potentiation was antagonized by SCH23390, a dopamine D(1) antagonist. Moreover, ebastine enhanced the central dopamine turnover ratio, but cetirizine could not, in this study.. Taken together, the potentiation of place preference of dihydrocodeine with ebastine may be due, at least in part, to stimulation of the central dopaminergic system via D(1) receptors. However, combination of dihydrocodeine with cetirizine does not potentiate place preference at all, nor does it potentiate the central dopaminergic system. Thus, it is likely that cetirizine may be a useful constituent in opioid-containing, antitussive preparations that would not potentiate the development of psychological dependence.

Topics: Animals; Antitussive Agents; Butyrophenones; Cetirizine; Codeine; Dopamine; Dose-Response Relationship, Drug; Histamine H1 Antagonists; Limbic System; Male; Mice; Mice, Inbred ICR; Piperidines; Receptors, Dopamine D1; Reward