Are Tacrolimus Pharmacokinetics Affected by Nephrotic Stage?

Therapeutic drug monitoring in childhood idiopathic nephrotic syndrome: a state of the art review

Immunosuppressants are commonly used as steroid-sparing agents in childhood idiopathic nephrotic syndrome (NS) to induce and sustain remissions. These drugs have narrow therapeutic indices with high inter- and intra-patient variability. Therapeutic drug monitoring (TDM) would therefore be essential to guide the prescription. Multiple factors in NS contribute to additional variability in drug concentrations, especially during relapses. In this article, we review the currently available evidence of TDM in NS and suggest a practical approach for clinicians' reference.

Off-label use of tacrolimus in children with glomerular disease: Effectiveness, safety and pharmacokinetics

Glomerular diseases are leading causes of end-stage renal disease in children. Tacrolimus is frequently used off-label in the treatment of glomerular diseases. The effectiveness, safety and pharmacokinetic data of tacrolimus in the treatment of glomerular diseases in children are reviewed in this paper to provide evidence to support its rational use in clinical practice. The remission rates in previously published studies were different. In 19 clinical trials on children with nephrotic syndrome, the overall remission rate was 52.6-97.6%. In four clinical trials on children with lupus nephritis, the overall remission rate was 81.8-89.5%. In a pilot study with paediatric Henoch-Schönlein purpura nephritis patients, the overall remission rate was 100.0%. Infection, nephrotoxicity, gastrointestinal symptoms and hypertension are the most common adverse events. Body weight, age, CYP3A5 genotype, cystatin-C and daily dose of tacrolimus may have significant effects on the pharmacokinetics of tacrolimus in children with glomerular disease. More prospective controlled trials with long follow-up are needed to demonstrate definitely the effectiveness, safety and pharmacokinetics of tacrolimus in children with glomerular diseases.

Time- and NADPH-Dependent Inhibition on CYP3A by Gomisin A and the Pharmacokinetic Interactions between Gomisin A and Cyclophosphamide in Rats

The traditional Chinese medicine Schisandra chinensis has remarkable protective effects against chemical-induced toxicity. Cyclophosphamide (CTX), in spite advances in chemotherapy and immunosuppressive regimes, is prone to cause severe toxicity due to its chloroacetaldehyde (CAA) metabolite produced by CYP3A. Our previous study identified that S. chinensis extract (SCE) co-administration potently decreased CAA production and attenuated liver, kidney and brain injuries in CTX-treated rats. Gomisin A (Gom A) is proved to be one of the most abundant bioactive lignans in S. chinensis with a significant CYP3A inhibitory effect. To find out whether and how Gom A participated in the chemoprevention of SCE against CTX toxicity, the Gom A-caused CYP3A inhibition in vitro as well as the pharmacokinetic interactions between Gom A and CTX in vivo were examined in this study. Using human liver microsomes, a reversible inhibition assay revealed that Gom A was a competitive inhibitor with a K_I value of 1.10 µM, and the time- and NADPH-dependent CYP3A inhibition of Gom A was observed in a time-dependent inhibition assay (K_I = 0.35 µM, k_inact = 1.96 min⁻¹). Hepatic CYP3A mRNA expression experienced a significant increase in our rat model with Gom A administration. This explained why CAA production decreased in the 0.5 h- and 6 h-pretreatment rat groups while it increased in the 24 h- and 72 h-pretreatment groups, indicating a bidirectional effect of Gom A on CYP3A-mediated CTX metabolism. The present study suggested that Gom A participates like SCE in the pharmacokinetic intervention of CTX by blocking CYP3A-mediated metabolism and reducing CAA production, and thus plays an important role in the chemopreventive activity of S. chinensis against CTX toxicity, in addition to the previously recognized protective effects. Also, the combined use of S. chinensis preparation or other drugs containing Gom A as the main component with CTX needed to be addressed for better clinical intervention.