Population Pharmacokinetics of Naloxegol in Pediatric Subjects Receiving Opioids

The pharmacokinetics (PK) of naloxegol were characterized in pediatric subjects, aged 6 months or older to less than 18 years who either have or are at risk of developing opioid-induced constipation following single dose administration. Subjects grouped as aged 12 years or older to less than 18 years, 6 months or older to less than 12 years, and 6 months or older to less than 6 years, received a single oral dose of naloxegol at doses that were estimated to achieve plasma exposures comparable to adult 12.5- or 25-mg doses. Intensive and sparse plasma naloxegol samples were collected to assess naloxegol concentrations. Data were combined with previously collected adult PK data and used to estimate PK parameters using population PK analyses. Naloxegol PK was described using a 2-compartment model with Weibull-type absorption. Neither age nor body weight was identified as a significant covariate indicating similar PK properties in adult and pediatric subjects. PK estimates in the youngest age group were approximately 80% less than those in adults (12.5-mg equivalent dose). Exposures in the other pediatric groups were similar to those in adult equivalent doses. The PK of naloxegol were characterized as linear over the dose range, with no clinically significant covariates and comparable PK characteristics in adults and pediatric subjects aged 6 months or older.