Optimal Trough Concentration of Tacrolimus in Pediatric Patients With Primary Nephrotic Syndrome

The trough concentration ( C 0 ) of tacrolimus in children with nephrotic syndrome (NS) has rarely been explored, so its target level was based on transplant research. This study aimed to determine the optimal tacrolimus C 0 in NS children. Data from primary NS children treated with tacrolimus at Wuhan Children's Hospital in the last 10 years were retrospectively collected. According to the cutoff C 0 analyzed by receiver‐operator characteristics (ROC) analysis, patients were divided into very low‐ (< 4 ng/mL), low‐ (4–5 ng/mL), medium‐ (5–7 ng/mL), and high‐concentration (7–10 ng/mL) groups. A total of 196 patients were enrolled for primary outcome analysis. Compared to medium‐concentration group, only the very low‐concentration group obtained significant inferior primary outcomes, including overall remission rate, relapse‐free survival rate, and relapse rate at 6 months. For secondary outcomes, the very low‐concentration group experienced more frequent treatment failure in 12 months, whereas the high‐concentration group suffered a higher risk of adverse events than the medium‐concentration group. For steroid‐resistant NS, very low‐ and low‐concentration groups required longer time to achieve remission compared to medium‐concentration group. For steroid‐sensitive NS, the very low‐concentration group suffered a higher relapse frequency than medium‐concentration group. Lastly, the dose of tacrolimus required for children with different CYP3A5 genotypes with or without Wuzhi capsules was analyzed. In conclusion, tacrolimus may be targeted to C 0 of 4–7 ng/mL during the first 6 months in children with NS. For steroid‐resistant NS, C 0 of 5–7 ng/mL can achieve a rapid remission.