The study design combines a long-term safety and a dose range determination objective. The first 8 weeks of the study were primarily intended for the dose range determination, while the later visits were used for the comparison of long-term safety between the groups.

Inclusion Criteria:

• Childhood functional constipation
• 6 months to <16 years of age
• Male or female
• For females of childbearing potential (after menarche): negative pregnancy test
• Moderately severe to severe constipation, defined as stool frequency <3 stools/week
• Informed consent signed by parent(s) or legal acceptable representative(s), after sufficient oral and written information before entering the study, to be documented by the investigators in the Case Report Form

Exclusion Criteria:

• Functional non-retentive fecal incontinence
• Known metabolic or endocrine disorders (s.a. hypothyroidism)
• Neurologic disorders (s.a. spina bifida or spinal cord anomaly)
• Hirschsprung's disease (congenital megacolon)
• Anal anomaly
• Gastrointestinal surgery
• Drug induced constipation
• Mental retardation
• Cerebral palsy
• Treatment with other laxatives
• Drugs influencing gastrointestinal function (e.g., cisapride, erythromicin, imodium)
• Prior bowel surgery, except appendectomy
• Earlier participation in this trial
• Concurrent participation in any other clinical trial
• Participation in any other clinical study 6 months prior to inclusion
• Any use of a Macrogol within 2 months prior to inclusion