Clinically significant drug‐drug interaction between tacrolimus and fluconazole in stable renal transplant recipient and literature review

WHAT IS KNOWN AND OBJECTIVE: Clinical use of fluconazole against fungal infections in renal transplant patients is complicated by the potentially marked and unpredictable drug-drug interactions (DDIs). We report a case of tacrolimus-fluconazole DDI in a stable renal transplant recipient and describe the mechanism, magnitude and duration of this DDI through a literature review. CASE SUMMARY: A 38-year-old woman experienced a 9.1-fold increase in dose-normalized tacrolimus trough level (trough concentration/weight-normalized daily dose) and an 87% decrease in weight-normalized daily dose (daily dose/body weight) in the treatment of documented Candida albicans oesophagitis by fluconazole. After discontinuation of fluconazole for 161 day, a 26% reduction in weight-normalized daily dose was required to maintain therapeutic exposure. WHAT IS NEW AND CONCLUSION: Oral fluconazole has a more significant impact on its drug interactions with tacrolimus than intravenous fluconazole. Gene screening for CYP3A5 6986 A>G and ABCB1 3435 C>T in organ transplant recipients may help in preventing DDI and facilitating tacrolimus dose adjustment.