Population Pharmacokinetic and Pharmacodynamic Modeling of Fesoterodine in Pediatric Patients with Neurogenic Detrusor Overactivity.

Fesoterodine is a muscarinic receptor antagonist approved for the treatment of overactive bladder (OAB) in adults and neurogenic detrusor overactivity (NDO) in pediatric patients. This work aimed to characterize the population pharmacokinetics of 5-hydroxymethyl tolterodine (5-HMT, the active metabolite of fesoterodine) and its pharmacokinetic/pharmacodynamic relationship in pediatric patients with OAB or NDO following administration of fesoterodine.

5-HMT plasma concentrations from 142 participants of age ≥ 6 years were analyzed, and a nonlinear mixed-effects model was developed. Weight-based simulations of 5-HMT exposure and maximum cystometric capacity (MCC) were conducted using the final models.

A one-compartment model with first-order absorption and a lag time, which included the effects of body weight, sex, cytochrome (CYP) 2D6 metabolizer status and fesoterodine formulation on pharmacokinetic parameters, best described the 5-HMT pharmacokinetics. An Emax model described the exposure-response relationship adequately. The median maximum concentration at steady state for pediatric patients weighing 25-35 kg and receiving 8 mg once daily (QD) was estimated to be 2.45 times greater than that in adults receiving 8 mg QD. Furthermore, simulation results showed dosing with fesoterodine 4 mg QD to pediatric patients weighing 25-35 kg and 8 mg QD to pediatric patients weighing >35 kg would achieve adequate exposure to demonstrate a clinically meaningful change from baseline (CFB) MCC.

Population models were developed for 5-HMT and MCC in pediatric patients. Weight-based simulations indicated that 4 mg QD for pediatric patients weighing 25-35 kg and 8 mg QD for those weighing > 35 kg provided similar exposures to those in adults following 8 mg QD and a clinically meaningful CFB MCC.

NCT00857896, NCT01557244.

Fesoterodine is a muscarinic receptor antagonist approved for the treatment of overactive bladder (OAB) in adults and neurogenic detrusor overactivity (NDO) in pediatric patients in the US. Population pharmacokinetic and pharmacokinetic/pharmacodynamic models were developed for 5-HMT based on data from two pediatric clinical trials that included 142 patients of age ≥ 6 years with OAB or NDO. Weight-based simulations of 5-HMT exposure and maximum cystometric capacity were conducted using the final models to examine the impact of covariates on 5-HMT exposure and the exposure–response profile. The results of these simulations indicate that 4 mg QD for pediatric patients weighing 25–35 kg and 8 mg QD for those weighing > 35 kg provide similar exposures to those in adults following 8 mg QD.

European journal of drug metabolism and pharmacokinetics. 2023 Mar 09 [Epub ahead of print]

Yamato Sano, Satoshi Shoji, Mohamed Shahin, Kevin Sweeney, Amanda Darekar, Bimal K Malhotra

Pfizer R&D Japan, Tokyo, Japan. ., Pfizer R&D Japan, Tokyo, Japan., Pfizer Inc., Groton, CT, USA., Pfizer R&D UK Ltd., Walton Oaks, Tadworth, UK., Pfizer Inc., New York, NY, USA.