CYP3A5*1/*3 genotype influences the blood concentration of tacrolimus in response to metabolic inhibition by ketoconazole

    loading  Checking for direct PDF access through Ovid



Ketoconazole retards metabolic degradation of tacrolimus through its effect on the cytochrome P-450 enzyme system and allows reduction in treatment costs. Enzyme activity is determined by a single nucleotide polymorphism (*1/*3) in the CYP3A5 gene.


We prospectively investigated the impact of this polymorphism on tacrolimus concentration in a cohort of 79 renal transplant recipients on ketoconazole. Genotyping was carried out by using polymerase chain reaction-restriction fragment length polymorphism technique. Dose-adjusted trough level (C0) was calculated at baseline and at 3, 7, 15, 30, and 60 days.


The baseline C0 was significantly lower in those with at least one *1 allele [44.95±14.12 vs. 63.43±14.72 (ng/ml)/(mg/kg/day), P<0.0001]. After starting ketoconazole in all genotypes, dose-normalized C0 increased and the cost of therapy decreased. Compared with baseline, the magnitude of increase was 112% and 79% in those without and with *1 allele, respectively (P<0.001). The cost savings were 32% and 39% in mycophenolate mofetil-treated and 47% and 61% in azathioprine-treated patients who were with and without one *1 allele, respectively.


We show that the CYP3A5*1/*3 polymorphism is an important determinant of the response to inhibition of tacrolimus metabolism by ketoconazole, with a 30% greater inhibition in those lacking *1 allele. This finding will allow better dose adjustment and minimize exposure to subtherapeutic or toxic concentrations.

Related Topics

    loading  Loading Related Articles