title: Drug interactions and interindividual variability of ciclosporin metabolism in the small intestine.
abstract: The undecapeptide ciclosporin is used as immunosuppressant after organ transplantation and for therapy of immune diseases. Low and variable bioavailability of ciclosporin has been attributed to its metabolism in the small intestine. The aim of the present study was to investigate drug interactions and interindividual variability of ciclosporin metabolism in the small intestine. Ciclosporin metabolism was studied in vitro using microsomes isolated from the small intestine of humans and pigs. The metabolites generated were quantified by HPLC and identified by mass spectrometry. Using specific antibodies and inhibitors, we showed that, as in the liver, cytochrome P450 3A (CYP 3A) enzymes are responsible for ciclosporin metabolism in the human small intestine. Of the 28 xenobiotics included in the study, 16 drugs, all well-known CYP 3A inhibitors, inhibited ciclosporin metabolism in the small intestine. In the small intestine of different patients, the rate of metabolism varied by a factor of 10. Ciclosporin was metabolized faster by small intestine microsomes from female (n = 4) than from male (n = 10) patients (p < 0.009).
authors.affiliation: Institut fur Allgemeine Pharmakologie, Medizinische Hoschshule Hannover, Deutschland.
authors.forename: A
authors.initials: A
authors.lastname: Lampen
authors.forename: U
authors.initials: U
authors.lastname: Christians
authors.forename: A
authors.initials: A
authors.lastname: Bader
authors.forename: I
authors.initials: I
authors.lastname: Hackbarth
authors.forename: K F
authors.initials: KF
authors.lastname: Sewing
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016572:Cyclosporine / Q000378:metabolism*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000494:pharmacology; D004347:Drug Interactions; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000378:metabolism*; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000166:cytology / Q000187:drug effects; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects; D008875:Middle Aged; D006899:Mixed Function Oxygenases / Q000494:pharmacology; D014217:Troleandomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D007166:Immunosuppressive Agents; D016572:Cyclosporine; D003577:Cytochrome P-450 Enzyme System; D014217:Troleandomycin; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A