RESUMEN
Realgar-Indigo naturalis formula (RIF) is a traditional Chinese medicine containing As4S4 and effective in treating acute promyelocytic leukemia (APL). The dose of RIF remains to be determined in pediatric patients. Comparison of plasma arsenic concentrations and toxicity between RIF and arsenic trioxide (ATO) treatment in APL may help to establish an appropriate therapeutic dose of RIF for children. From October 2018 to March 2020, 19 pediatric patients with APL treated with SCCLG-APL protocol were included, 9 in RIF group at 135 mg/kg/day orally three times daily, and 10 in ATO group at 0.16 mg/kg/day intravenously over 12 h daily. Peak and trough plasma arsenic concentrations were assayed at D1, 2, 7 and 14 of induction treatment. Urine arsenic excretions were assessed with spot urine samples and the measurements were adjusted using creatinine. Toxicities were compared between two groups. The plasma arsenic concentration reached steady state at D7 either in the RIF or ATO group, and the mean peak and trough concentrations were similar between two groups (P > 0.05), which were 0.54 µmol/L and 0.48 µmol/L in RIF group, and 0.63 µmol/L and 0.51 µmol/L in ATO group, respectively. Urine arsenic excretion rate was positively correlated with the concentration of plasma arsenic. The rates of treatment-related adverse events were similar in two groups. In conclusion, the dose of RIF at 135 mg/kg/day may be an appropriate therapeutic dose in children with APL. Urine arsenic level can be used as an indicator to estimate plasma arsenic concentration. Trial registration www.clinicaltrials.gov NCT02200978.