This study is to determine the pharmacokinetics of a new drug for the treatment of constipation in children. The purpose of the study is to determine the preliminary safety and efficacy of a single dose of 0.03 mg/kg prucalopride (R108512) in pediatric subjects aged <4 to >12 years with functional fecal retention. This dose corresponds to an adult dose of 1.5-2.0 mg of prucalopride.