title: Clinical relevance of sirolimus drug interactions in transplant patients.
abstract: Sirolimus, a new immunosuppressant drug; is metabolized by cytochrome P450 3A4 (CYP3A4) and is a substrate of the P-glycoprotein drug efflux pump. The CYP3A4/P-glycoprotein system is mainly localized in the liver and intestine. It is responsible for the severe first pass metabolism of sirolimus with a low bioavailability. Drugs like voriconazole, itraconazole, fluconazole, and erytrhomycin may decrease the metabolic activity of this enzymatic system. This report documents in five patients that coadministration of these antimicrobials with sirolimus increases the blood concentrations of the immunosuppressant. The dose-normalized trough blood concentration showed a mean increase of sevenfold with the coadministration of these drugs. It is essential to monitor the blood sirolimus concentrations and to adjust the sirolimus doses before and after coadministration of these drugs.
authors.affiliation: Department of Clinical Pharmacology, University Clinic of Navarra, Pamplona, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Sádaba
authors.forename: M A
authors.initials: MA
authors.lastname: Campanero
authors.forename: E G
authors.initials: EG
authors.lastname: Quetglas
authors.forename: J R
authors.initials: JR
authors.lastname: Azanza
mesh_terms: D000368:Aged; D000935:Antifungal Agents / Q000627:therapeutic use*; D019540:Area Under Curve; D001711:Biotransformation; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004347:Drug Interactions; D016027:Heart Transplantation / Q000276:immunology / Q000502:physiology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008297:Male; D011743:Pyrimidines / Q000627:therapeutic use*; D020123:Sirolimus / Q000493:pharmacokinetics / Q000627:therapeutic use*; D014230:Triazoles / Q000627:therapeutic use*; D065819:Voriconazole
chemical_list: D000935:Antifungal Agents; D007166:Immunosuppressive Agents; D011743:Pyrimidines; D014230:Triazoles; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D065819:Voriconazole; D020123:Sirolimus