title: Corticosteroid interactions with cyclosporine, tacrolimus, mycophenolate, and sirolimus: fact or fiction?
abstract: OBJECTIVE
  To review the current clinical evidence on the effects of corticosteroid interactions with the immunosuppressive drugs cyclosporine, tacrolimus, mycophenolate, and sirolimus.
  
  
  METHODS
  Articles were retrieved through MEDLINE (1966-February 2008) using the terms corticosteroids, glucocorticoids, immunosuppressants, cyclosporine, tacrolimus, mycophenolate, sirolimus, drug interactions, CYP3A4, P-glycoprotein, and UDP-glucuronosyltransferases. Bibliographies were manually searched for additional relevant articles.
  
  
  METHODS
  All English-language studies dealing with drug interactions between corticosteroids and cyclosporine, tacrolimus, mycophenolate, and sirolimus were reviewed.
  
  
  RESULTS
  Corticosteroids share common metabolic and transporter pathways, the cytochrome P450 and P-glycoprotein (P-gp/ABCB1) systems, respectively, with cyclosporine, tacrolimus, and sirolimus. As a group, corticosteroids induce the CYP3A4 and P-gp pathways; however, a few exceptions exist and the impact on a patient's immunosuppressant regimen may be critical. Corticosteroids also have demonstrated an induction effect on the uridine diphosphate-glucuronosyltransferase enzymes and multidrug resistance-associated protein 2 involved in mycophenolate's disposition. Successful corticosteroid withdrawal regimens have been reported; however, only few studies have examined the effects of steroid withdrawal on the remaining immunosuppressive regimens. To date, the clinical impact of steroid withdrawal on disposition of other immunosuppressive agents is not well characterized, and reports of such drug-drug interactions are conflicting.
  
  
  CONCLUSIONS
  While our understanding of the clinical impact of steroid-immunosuppressant interactions is limited, it remains a fact that corticosteroids have complex induction and inhibition interactions with common metabolic and transport pathways. Given the complex interaction of corticosteroids on crucial metabolic enzymes and transporter proteins, monitoring of immunosuppressive agents during steroid withdrawal is warranted to ensure optimal treatment outcomes.
authors.affiliation: Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Lam
authors.forename: Nilufar
authors.initials: N
authors.lastname: Partovi
authors.forename: Lillian S L
authors.initials: LS
authors.lastname: Ting
authors.forename: Mary H H
authors.initials: MH
authors.lastname: Ensom
mesh_terms: D000305:Adrenal Cortex Hormones / Q000494:pharmacology*; D016572:Cyclosporine / Q000493:pharmacokinetics*; D004347:Drug Interactions; D006801:Humans; D007166:Immunosuppressive Agents / Q000493:pharmacokinetics*; D009173:Mycophenolic Acid / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D020123:Sirolimus / Q000493:pharmacokinetics*; D016559:Tacrolimus / Q000493:pharmacokinetics*; D014180:Transplantation
chemical_list: D000305:Adrenal Cortex Hormones; D007166:Immunosuppressive Agents; D016572:Cyclosporine; D009173:Mycophenolic Acid; D020123:Sirolimus; D016559:Tacrolimus