Tacrolimus Dose Requirement in Iranian Kidney Transplant Recipients within the First Three Weeks after Transplantation

BACKGROUND: Tacrolimus is the main immunosuppressive agent in many kidney transplant protocols with an initial recommended daily dose of 0.2 mg/kg of ideal body weight (IBW). However, due to the high inter- and intra-patient variability in its pharmacokinetics, the required tacrolimus doses may differ markedly from patient to patient. OBJECTIVE: To assess the required tacrolimus dose to achieve the desired whole blood concentration within the first three weeks after kidney transplantation among Iranian patients. METHODS: This cross-sectional study was performed at kidney transplantation ward of Imam Khomeini Hospital Complex where almost all patients receive thymoglobulin induction therapy and a calcineurin inhibitor, mainly tacrolimus, plus mycophenolate, and prednisolone as maintenance immnosuppressive drugs with the target tacrolimus whole blood concentration of 8–12 ng/mL for the first month after transplantation. RESULTS: The mean±SD administered daily dose of tacrolimus during the first three weeks after transplantation was 0.085±0.024 mg/kg of IBW that resulted in a mean±SD whole blood concentration of 10.34±5.44 ng/mL. The required mean±SD dose of the drug to achieve the desired whole blood level of 8–10 ng/mL was 0.08±0.02 mg/kg. Only 27.4% of the assessed tacrolimus blood levels were within the desired range. Compared with males, females needed 19% more daily dose of tacrolimus to reach similar whole blood levels. Tacrolimus blood levels were significantly correlated with daily tacrolimus doses (r=0.307, p=0.001) and patients’ age (r=0.283, p=0.003). CONCLUSION: It seems that Iranian kidney transplant recipients need lower daily doses of tacrolimus to achieve the desired whole blood levels; compared with males, females need a higher dose.