A Safety and Efficacy Study of a Range of Linaclotide Doses Administered Orally to Children Ages 7-17 Years, With Irritable Bowel Syndrome With Constipation

Inclusion Criteria: * Patient weighs at least 18 kg (39.7 lbs) * Patient meets Rome III criteria for child/adolescent IBS: at least once per week for at least 2 months before Screening Visit, the patient experienced abdominal discomfort (an uncomfortable sensation not described as pain) or pain associated with 2 or more of the following at least 25% of the time: * a) Improvement with defecation * b) Onset associated with a change in frequency of stool * c) Onset associated with a change in form (appearance) of stool * Patient meets modified Rome III criteria for child/adolescent Functional Constipation (FC): For at least 2 months before the Screening Visit, the patient has had 2 or fewer defecations (with each defecation occurring in the absence of any laxative, suppository, or enema use during the preceding 24 hours) in the toilet per week. In addition, at least once per week, patient meets 1 or more of the following: * a) History of retentive posturing or excessive volitional stool retention * b) History of painful or hard bowel movements (BMs) * c) Presence of a large fecal mass in the rectum * d) History of large diameter stools that may obstruct the toilet * Patient is willing to discontinue any laxatives used before the Pretreatment Visit in favor of the protocol-permitted rescue medicine * Patient has an average of fewer than 3 spontaneous BMs (SBMs) per week during the 14 days before the randomization day and up to the randomization. An SBM is defined as a BM that oc…