In Vitro Metabolism of Clindamycin in Human Liver and Intestinal Microsomes

Abstract

This article is available online at http://dmd.aspetjournals.org ABSTRACT:Incubations with human liver and gut microsomes revealed that the antibiotic, clindamycin, is primarily oxidized to form clindamycin sulfoxide. In this report, evidence is presented that the Soxidation of clindamycin is primarily mediated by CYP3A. This conclusion is based upon several lines of in vitro evidence, including the following. 1) Incubations with clindamycin in hepatic microsomes from a panel of human donors showed that clindamycin sulfoxide formation correlated with CYP3A-catalyzed testosterone 6␤-hydroxylase activity; 2) coincubation with ketaconazole, a CYP3A4-specific inhibitor, markedly inhibited clindamycin S-oxidase activity; and 3) when clindamycin was incubated across a battery of recombinant heterologously expressed human cytochrome P450 (P450) enzymes, CYP3A4 possessed the highest clindamycin S-oxidase activity. A potential role for flavin-containing monooxygenases (FMOs) in clindamycin S-oxidation in human liver was also evaluated. Formation of clindamycin sulfoxide in human liver microsomes was unaffected either by heat pretreatment or by chemical inhibition (e.g., methimazole). Furthermore, incubations with recombinant FMO isoforms revealed no detectable activity toward the formation of clindamycin sulfoxide. Beyond identifying the drug-metabolizing enzyme responsible for clindamycin S-oxidation, the ability of clindamycin to inhibit six human P450 enzymes was also evaluated. Of the P450 enzymes examined, only the activity of CYP3A4 was inhibited (ϳ26%) by coincubation with clindamycin (100 M). Thus, it is concluded that CYP3A4 appears to account for the largest proportion of the observed P450 catalytic clindamycin S-oxidase activity in vitro, and this activity may be extrapolated to the in vivo condition.Clindamycin (methyl 7-chloro-6,7,8-trideoxy-6-[(2S,4R)-1-methyl-4-propylpyrrolidine-2-carboxamido]-1-thio-1-threo-D-galacto-octopyranoside monohydrochloride) is an antibiotic of the "lincosamide" class (Brodasky et al., 1968). The lincosamide antibiotics seem to be most useful against the bacteria classified as Gram-positive cocci. In addition, clindamycin is helpful against protozoans such as Toxoplasma and Mycoplasma as well as many anaerobic bacteria (Luft and Remington, 1988;Dannemann et al., 1991;Mazur et al., 1999).In humans, absorption of clindamycin is rapid and virtually complete (90%) following oral administration (DeHaan et al., 1972;Metzler et al., 1973). Concentrations of clindamycin in the serum increase linearly with increased dose, and levels exceed the minimum inhibitory concentration for most indicated organisms for at least 6 h following administration of the recommended dose. Clindamycin is widely distributed throughout the body and has an average biological half-life of 2.4 h. The major bioactive metabolites excreted in urine and feces are clindamycin sulfoxide and N-desmethylclindamycin (Seaberg et al., 1984;Flaherty et al., 1988;Gatti et al., 1998).To date, there are no published reports tha...

Applying Biopharmaceutical Classification System (BCS) Criteria to Predict Oral Absorption of Drugs in Dogs: Challenges and Pitfalls

“…Efforts to predict drug absorption (or to understand the causative factors impacting interspecies differences in F) is dependent upon a wide array of variables including API solubility and permeability (BCS), formulation factors, and physiological variables (including regional permeability differences, which could differ between species), GI pH, luminal and mucosal enzymology, and intestinal motility, first-pass drug metabolism, and transporter activity (92)(93)(94)(95)(96). It is for this reason that a blending of BCS and the BDDCS may provide far better predictions of canine versus human drug absorption characteristics than would either classification system alone.…”

“…When considering sources of potential interspecies divergence, the important physiologic variables include GI fluid pH and composition, intestinal transit time, mucosal surface area, and the size and density of intestinal intercellular pores (92)(93)(94)(95). These factors are particularly influential in the absorption of low solubility and/or low permeability drugs and may be helpful to predict interspecies differences in food effects (96).…”

Mammalian flavin-containing monooxygenases: structure/function, genetic polymorphisms and role in drug metabolism

“…Unfortunately, antibodies directed toward FMOs typically inhibit catalytic activity weakly, if at all, and the only chemical inhibitors are competitive substrates. The most commonly used alternative substrate to inhibit FMO in vitro (Mani et al, 1993;Narimatsu et al, 1999;Rawden et al, 2000;Pike et al, 2001;Attar et al, 2003;Wynalda et al, 2003;Virkel et al, 2004) and in vivo (Ruse & Waring, 1991;Nace et al, 1997;Wang et al, 2000) has been methimazole (see next section for further discussion of methimazole). FMO activity is unaffected by non-ionic detergent or carbon monoxide, but most FMOs are readily inhibited by short incubations at temperatures of 45-50 °C.…”

“…FMO readily S-oxygenates simple sulfides such as methyl-, ethyl-, ethyl methyl, 4-chlorophenyl methyl, and diphenyl sulfides Nnane & Damani, 2003a. Sulfide-containing drugs, for which FMO is active in S-oxygenation to sulfoxides, include cimetidine, rantidine, thioridazine, 7-(1,3-thiazolidin-2-methyl) theophylline, (+)-cis-3,5-dimethyl-2-(3-pyridyl)-thiazolidin-4-one, sulindac sulfide, clindamycin, albendazole, and fenbendazole (Eriksson & Bostrom, 1988;Grosa et al, 1992;Cashman et al, 1993b;Lanusse et al, 1993;Moroni et al, 1995a;Nunoya et al, 1995;Hamman et al, 2000;Rawden et al, 2000;Nnane & Damani, 2003aWynalda et al, 2003;Virkel et al, 2004). Although not employed as a therapeutic drug, the cyclic sulfide tetrahydrothiophene is the best substrate to date, as evidenced by submicromolar K m values, found by us with FMO.…”

A Comprehensive in Vitro and in Silico Analysis of Antibiotics That Activate Pregnane X Receptor and Induce CYP3A4 in Liver and Intestine

“…Similarly, although clindamycin elicited substantial increases in PXR activation, CYP3A4mRNA, and protein, its failure to produce a significant increase in the rate of 6␤-hydroxytestosterone formation could reflect its modest ability to inhibit CYP3A4 (Wynalda et al, 2003).…”