Initial dose optimization of tacrolimus for children with systemic lupus erythematosus based on theCYP3A5polymorphism and coadministration with Wuzhi capsule

Tacrolimus, an immunosuppressant, has been used to treat paediatric systemic lupus erythematosus, but the optimal initial regimen is not clear. The purpose of this study was to explore the optimal initial dose of tacrolimus for children with systemic lupus erythematosus using population pharmacokinetics and pharmacogenomics.Clinical information, tacrolimus concentrations and related genetic polymorphisms were incorporated into a model using non-linear mixed-effects modelling (NONMEM) analysis.The results showed that weight, the CYP3A5 genotype and combined treatment with Wuzhi capsule can affect tacrolimus clearance in children with systemic lupus erythematosus. Furthermore, at the same weight, the ratios of tacrolimus clearance were 1:2.49:0.57:1.4193 from people who were CYP3A5*3/*3 and did not take Wuzhi capsule, people who had the CYP3A5*1 allele and did not take Wuzhi capsule, people who were CYP3A5*3/*3 and took Wuzhi capsule, and people who had the CYP3A5*1 allele and took Wuzhi capsule, respectively. In addition, we found that 0.10 mg/kg split into two doses was suitable for people with weights from 10 to 60 kg who were CYP3A5*3/*3 and did not take Wuzhi capsule, who were CYP3A5*3/*3 and took Wuzhi capsule, and who had the CYP3A5*1 allele and took Wuzhi capsule. In people who had the CYP3A5*1 allele and did not take Wuzhi capsule, 0.15 mg/kg split into two doses was appropriate for those with weights from 10 to 40 kg and 0.10 mg/kg split into two doses was appropriate for those with weights from 40 to 60 kg.This study is the first study to recommend an optimal initial regimen of tacrolimus for children with systemic lupus erythematosus based on the CYP3A5 polymorphism and coadministration of Wuzhi capsule.