Escitalopram and Sertraline Population Pharmacokinetic Analysis in Pediatric Patients

Background and Objective Escitalopram and sertraline are commonly prescribed for anxiety and depressive disorders in children and adolescents. The pharmacokinetics (PK) of these medications have been evaluated in adults and demonstrate extensive variability, but studies in pediatric patients are limited. Therefore, we performed a population PK analysis for escitalopram and sertraline in children and adolescents to characterize the effects of demographic, clinical, and pharmacogenetic factors on drug exposure. Methods A PK dataset was generated by extracting data from the electronic health record and opportunistic sampling of escitalopram- and sertraline-treated psychiatrically hospitalized pediatric patients aged 5–18 years. A population PK analysis of escitalopram and sertraline was performed using NONMEM. Concentration-time profiles were simulated using MwPharm++ to evaluate how covariates included in the final models influence medication exposure and compared to adult therapeutic reference ranges. Results The final escitalopram cohort consisted of 315 samples from 288 patients, and the sertraline cohort consisted of 265 samples from 255 patients. A one-compartment model with a proportional residual error model best described the data for both medications. For escitalopram, CYP2C19 phenotype and concomitant CYP2C19 inhibitors affected apparent clearance (CL/ F ), and normalizing CL/ F and apparent volume of distribution ( V / F ) to body surface area (BSA) improved estimations. The final escitalopram model estimated CL/ F and V / F at 14.2 L/h/1.73 m 2 and 428 L/1.73 m 2 , respectively. For sertraline, CYP2C19 phenotype and concomitant CYP2C19 inhibitors influenced CL/ F , and empirical allometric scaling of patient body weight on CL/ F and V / F was significant. The final sertraline model estimated CL/ F and V / F at 124 L/h/70 kg and 4320 L/70 kg, respectively. Normalized trough concentrations ( C trough ) for CYP2C19 poor metabolizers taking escitalopram were 3.98-fold higher compared to normal metabolizers (151.1 ng/mL vs 38.0 ng/mL, p < 0.0001), and normalized C trough for CYP2C19 poor metabolizers taking sertraline were 3.23-fold higher compared to normal, rapid, and ultrarapid metabolizers combined (121.7 ng/mL vs 37.68 ng/mL, p < 0.0001). Escitalopram- and sertraline-treated poor metabolizers may benefit from a dose reduction of 50–75% and 25–50%, respectively, to normalize exposure to other phenotypes. Conclusion To our knowledge, this is the largest population PK analysis of escitalopram and sertraline in pediatric patients. Significant PK variability for both medications was observed and was largely explained by CYP2C19 phenotype. Slower CYP2C19 metabolizers taking escitalopram or sertraline may benefit from dose reductions given increased exposure.