The pharmacokinetics, safety, and tolerability of mirabegron in children and adolescents with neurogenic detrusor overactivity or idiopathic overactive bladder and development of a population pharmacokinetic model–based pediatric dose estimation

Introduction Mirabegron, a selective beta 3-adrenoreceptor agonist, is a well-established alternative to antimuscarinics in adults with overactive bladder (OAB) symptoms and is under development for use in pediatric patients. Understanding drug pharmacokinetics (PK) in pediatric patients is needed to determine appropriate dosing. Conducting these studies is ethically complex, particularly as regulatory guidance requires that PK is assessed in pediatric patients with a therapeutic need for the drug. It is also vital to evaluate the safety/tolerability and palatability/acceptability of pediatric formulations. Purpose The purpose of the study was to characterize the PK of mirabegron in pediatric patients with neurogenic detrusor overactivity or idiopathic OAB, to provide a basis for a weight-based dosing algorithm, and to evaluate the safety, tolerability, and palatability/acceptability of the formulations. Materials and methods A preliminary population PK model constructed from adult data with allometric scaling was used to predict single weight-adjusted mirabegron doses. This was developed to achieve exposures in pediatric patients in two phase 1 studies that were consistent with steady state in adults following once-daily 25 mg ('low dose') and 50 mg ('high dose') dosing. In study 1, adolescents (12-<18 years) and children (5-<12 years) received a single tablet under fed or fasted conditions. In study 2, children (3-