Diltiazem does not always increase blood cyclosporin concentration

The pharmacokinetic interaction between the calcium channel blocking drug, diltiazem (DTZ), the antifungal agent itraconazole (ICZ) and the immunosuppressive drug cyclosporin (CsA) was studied in a patient with a single lung transplant. The CsA area under curve estimations demonstrated a significant increase when ICZ was co-prescribed (5836 mu g l(-1) h vs 8159 mu g l(-1) h) but no increase when DTZ was co-prescribed with CsA (5836 mu g l(-1) h vs 5069 mu g l(-1) h). Despite widespread use as a CsA-sparing agent, DTZ does not always increase CsA concentrations.