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Updated: Sep 28, 2025

Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS
Published on: November 8, 2015
Rapid clearance of tacrolimus blood concentration triggered by variant pharmacogenes
Livija Šimičević1, Iva Canjuga2, Lada Zibar2
1Department of Laboratory Diagnostics, Division of Pharmacogenomics & Therapy Individualization, University Hospital Centre Zagreb, Zagreb, Croatia.
What Is Known And Objective:
Tacrolimus (TAC) is an immunosuppressant with large interpatient pharmacokinetic variability and a narrow therapeutic index. We report a case of acute cellular rejection (ACR) type IB with insufficient TAC blood concentrations (TAC C0 ).
Case Summary:
ACR developed on the eighth postoperative day of kidney transplantation. During this period, TAC C0 were insufficient. This referred pharmacogenetic assessment disclosed the patient as a CYP3A5 expresser and CYP3A4*1B carrier. According to the genotype, higher doses of TAC, 15 mg twice daily, were administered and targeted TAC C0 were achieved.
What Is New And Conclusion:
Our case presents an association of TAC rapid clearance and two alleles modifying greater CYP3A enzyme activity.
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