Therapeutic Drug Monitoring of Tacrolimus in Tunisian Renal Transplant Patients during the Tuberculosis Infection: A Retrospective, Observational, Single-centre Analysis

Tuberculosis is a challenge in organ transplantation due to the interaction between Anti-Tuberculosis Treatment (ATT) and immunosuppressive drugs, such as Tacrolimus (TAC). This study aimed to assess this interaction and discuss the guidelines used in this specific case. Methods A retrospective, observational, single-center analysis was performed at the Department of Clinical Pharmacology (National Centre of Pharmacovigilance, Tunisia). We analyzed the database of patients who received TAC from 2009 until 2018. We included samples provided from renal transplant patients infected by Mycobacterium tuberculosis after transplantation. Trough blood levels (C0) were determined using an immunoassay analyzer. The Therapeutic Range (TR) of TAC was considered between 5 and 10 ng/mL. Pharmacokinetic parameters were compared between the period of co-administration of TAC/ATT (period A) and the period during which patients received only TAC (period B). Results Seven renal transplant patients treated by TAC were included. 41 samples were analyzed (16; period A, 25; period B). Only 6% of C0 values were found within TR during period A, while this rate was 44% during period B. During period A, 88% of TAC C0 was under the lower limit of TR, indicating a high risk of transplant rejection. The mean C0 and C0/D were significantly lower during period A (3.11 & PLUSMN;1.53 ng/mL vs 7.11 & PLUSMN; 3.37 ng/mL; p = 0.001 and 33.06 & PLUSMN; 24.89 vs 83.14 & PLUSMN; 44.46; p = 0.0006, respectively), without difference in doses between periods. Conclusion Considering the results of this study, clinicians are suggested to monitor TAC closely in this particular circumstance.