Inclusion Criteria:  Patients 8 - < 18 years of age who have a confirmed diagnosis of Pediatric functional constipation according to the Rome IV criteria, who give written informed consent personally or from their legal guardians. Discontinuation of any medication affecting gastrointestinal (GI) motility at least 2 weeks before starting the treatment allocation. Patient's daily diary that indicates an average of < 3 weekly spontaneous bowel movements (SBMs), with ≥ 25% of SBMs involving at least some straining and/or a 5-point modified Bristol Stool Form Scale type 1 or 2. Patients who completed the study protocol.  Exclusion Criteria:  If the patient's constipation is attributed to any of the following: physical, mental, or cognitive illness, inflammatory bowel disease, medication, anatomical, neurological, endocrine, or metabolic factors. If the patient is a candidate for or underwent abdominal surgery, or has any condition other than constipation that could affect gastrointestinal motility or defecation. Patients suffering from Hirschsprung's disease. Patients experiencing any alarming signs e.g. unexplained significant weight loss. Untreated fecal impaction at the time of enrollment.