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.