Search

Increased systemic exposure to statins and consequent risk for complications has been reported in patients concomitantly treated with cyclosporin A (CsA). This has been ascribed to inhibition of drug catabolism by cytochrome P450 3A4 (CYP3A4) or drug transport by P-glycoprotein (PGP) and organic anion transporting polypeptide (OATP1B1). It is not known whether the combination of statins and tacrolimus (Tac) also suffers from this drawback.Therefore, a pharmacokinetic study of atorvastatin and its metabolites was performed in 13 healthy volunteers after 4 days' treatment, and after short (12 h) concomitant exposure to CsA and Tac. A complementary assessment of overall CYP, and hepatic and intestinal CYP3A4 + PGP activity was performed after each treatment episode and compared to baseline (no drugs). Systemic exposure to atorvastatin acid and its metabolites was significantly increased when administered with CsA. In contrast, intake of Tac did not have any impact on atorvastatin pharmacokinetics. Concomitantly, a profound decrease of hepatic and intestinal PGP and an increase of intestinal CYP3A4 were noted with CsA, whereas no effect was seen after atorvastatin therapy with or without Tac. Based on these findings treatment with Tac appears a safer option for patients needing a combination of statins and calcineurin inhibitors.

This study aimed to determine the impact of maintenance immunosuppressive therapy with cyclosporin A (CsA), tacrolimus (FK506) and sirolimus (Rapa) on the in vivo activity of both intestinal and hepatic cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (PGP) in renal transplant patients. The activity of these four elimination pathways was measured by the recently validated intravenous (iv) and per oral (po)14C erythromycin breath and urine test. In addition, overall hepatic P450 activity was measured by the 13C aminopyrin breath test. Three groups of stable renal transplant patients on maintenance therapy with corticosteroids (CS) and mycophenolate mofetil (MMF) plus either CsA or FK506 or Rapa were examined. A significant increase in intestinal CYP3A4 activity and a significant decrease in hepatic and intestinal PGP activity was seen in patients on CsA in comparison with those on FK506 or Rapa (p < 0.01). A similar analysis in six healthy volunteers at baseline and after intake of CsA, FK506 and Rapa confirmed the results seen in the patients. There was no difference in CYP3A4 and PGP activity in the patients taking either FK506 or Rapa and healthy controls. These data suggest that a different pattern of drug interactions might be expected in patients treated with CsA vs. FK506/Rapa.

Diarrhea is the most frequently reported adverse event in patients treated with mycophenolate mofetil. Twenty-six renal transplant patients on a mycophenolate mofetil-based immunosuppressive regime with persistent afebrile diarrhea were examined. Diarrhea caused a significant rise in FK-506 trough levels despite intake of stable doses, necessitating FK-506 dose reductions of 30% to obtain pre-diarrhea trough levels. In contrast, trough levels of cyclosporine A remained stable without dose adjustments. This suggests that absorption and/or metabolism is differentially altered for FK506 compared with cyclosporine A in patients with diarrhea. In nine patients mycophenolate mofetil was reduced or stopped because of persistent diarrhea without identifiable cause. This resulted in end-stage renal disease because of chronic rejection in two patients, and in acute rejection in two patients, all taking FK506 and steroids. Therefore, dose adjustments of FK506 in patients with diarrhea must be carefully monitored, especially when doses of mycophenolate mofetil are also reduced.