[The pharmacokinetics of antilipemic agents. 5. Is 2-(4-hydroxyphenoxy)-2-methylpropionic acid a metabolite of the antilipemic ciprofibrate?]

Chromatographic resolution of ciprofibrate and interaction of the racemate and both enantiomers with rat liver microsomes in vitro

The enantiomers of ciprofibrate may be achieved by enantioselective HPLC separation of its methylesters using a OD - Daicel column. Ciprofibrates (racemate and both enantiomers) bind to oxidized cytochrome P-450 in rat liver microsomes according type II like aniline or most probably as inversed type I, but less pronounced and with a general shift to the left. Ethylmorphine N-demethylation, ethoxycoumarin and ethoxyresorufin O-deethylation are all inhibited by the ciprofibrates, most effectively ethoxyresorufin O-deethylation by S(-)-ciprofibrate even in microM concentrations. Microsomal luminol and lucigenin amplified chemiluminescence indicating the formation of reactive oxygen species, microsomal hydrogen peroxide formation and NADPH/Fe stimulated lipid peroxidation were inhibited in a concentration dependent manner in concentration ranges between mM and microM. This might be due to distinct scavenger activities of all 3 compounds: the zymosan stimulated chemiluminescence of whole blood was completely inhibited in mM concentrations and influenced significantly down to concentrations of 10 microM, whereas burst and phagocytosis tests with human polynuclear leucocytes were not influenced.

[The pharmacokinetics of hypolipemic agents. 10. The dehalogenation of the hypolipemic agent ciprofibrate]

rac-2 described as a metabolite of rac-1 was synthesized in four steps starting with rac-3. Partial dehalogenation occurs with LiAlH4. A new structure assignment of the resulting stereoisomers resulted from NMR spectroscopy. After oral administration of rac-1 in multiple dose studies to volunteers, rac-2 could not be detected within the limitations of sensitivity of HPLC (UV-detector) in plasma or in urine.

[Pharmacokinetics of hypolipedemic agents. 9. The question of biliary excretion of the hypolipidemic agent ciprofibrate (1) (2-(4-(2,2-dichlorocyclopropyl)-phenoxy)-2-methylpropionic acid]

After oral administration of 200 mg Ciprofibrate (1) to 10 patients, who were cholecystectomated with subsequent T-drainage, 1 could be determined in the collected bile only as its 1-O-beta-acylglucuronide to a very small amount. Approximative calculations have shown that two days after a single dose, less than 0.5% of the administered dose of 1 is excreted on the biliary route. It is an unsolved problem if there is an increase of biliary excretion after multiple dose.

[Ciprofibrate: erythrocyte partition coefficient and binding to serum protein]

The in vitro binding of the lipid lowering agent Ciprofibrat (1) to different plasma protein fractions and its red blood-cell partition coefficient were investigated. The binding-rate to albumin and alpha-globulin is dose-dependent (first order kinetic) and amounts to about 95% for albumin and to 25% for alpha-globulin. The affinity of 1 to beta- and gamma-globulin is non-specific and dose-independent (average binding-rate 8% and 10%, respectively). 1 shows only a weak affinity to erythrocytes, therefore, the red blood-cell partition coefficient is 0.02.

[The pharmacokinetics of hypolipemic agents. 6. Is 2-(4-(2,2-dichlorocyclopropyl)-phenoxy)-propane a metabolite of the hypolipemic ciprofibrate?]

According to earlier investigations 2-(4-(2,2-dichlorocyclopropyl)-phenoxy)-propane (4) ought to be a metabolite of the hypolipidemic agent ciprofibrate (1). However, 4 could not be detected in plasma or in urine after administration of a dose of 2100 mg 1 during the course of a multiple-dose-study. Therefore, the compound described in literature must be an unknown one and the existence of 4 as a metabolite of 1 is excluded.