Purpose: To evaluate the role of diltiazem on tacrolimus sparing in pediatric primary nephrotic syndrome (PNS) and its relation to CYP3A4, CYP3A5, ABCB1, and SLCO1B3 polymorphisms.
Methods: The PNS children treated with tacrolimus and with steady-state trough concentration (C0) were retrospectively collected. The impacts of diltiazem on tacrolimus dose-adjusted C0 (C0/D), target concentration achievement, and required dose were evaluated. Meanwhile, the relationship between the polymorphisms (including CYP3A4*1G, CYP3A5*3, ABCB1-C3435T, and SCLO1B3) and dose-sparing effect were investigated.
Results: A total of 71 children with 535 concentrations, including 16 children with concomitant diltiazem, were involved. Significantly increased C0/D (94.0 vs 83.8 ng/mL per mg/kg, p = 0.038) and lower required daily dose of tacrolimus (0.056 vs 0.064 mg/kg, p = 0.003) were observed in patients co-administered with diltiazem. Subpopulation carrying CYP3A4*1G, CYP3A5*1, ABCB1-3435TT, or SLCO1B3-699AA was presented with enhanced increment in tacrolimus C0/D by 38.8-102.9%.
Conclusion: Moderate effect of diltiazem on tacrolimus sparing, which might relate to the polymorphisms of CYP3A4, CYP3A5, ABCB1, and SLCO1B3, was documented.
Keywords: Diltiazem; Dose sparing; Drug-drug interaction; Polymorphisms; Primary nephrotic syndrome; Tacrolimus.