Eligibility Criteria:
Inclusion Criteria:
* meets diagnostic criteria for functional constipation. This includes loose stools that are rarely present without the use of laxatives and 2 or more of the following: straining during at least 25% of defecations; lumpy or hard stools in at least 25% of defecations; sensation of incomplete evacuation for at least 25% of defecations; sensation of anorectal obstruction/blockage for at least 25% of defecations; manual maneuvers to facilitate at least 25% of defecations \[e.g., digital evacuation, support of the pelvic floor\]; and fewer than 3 defecations per week. Criteria for functional constipation must be fulfilled for last 3 months, with symptom onset at least 6 months prior to diagnosis.
* willing to use study drug for up to 7 days as directed, and must agree to record bowel movements (frequency, consistency, etc.) accurately and consistently in a daily diary, and make 3 clinic visits.
* except for constipation, must be otherwise in good health, as determined by physical exam and medical history.
* agrees not to use any other products (drug, herbal, dietary supplements including fiber, etc.) to treat their constipation during the course of the study.
* agrees not to use any medication known to cause constipation during the course of the study.
* agree to maintain a similar diet from the week prior to randomization through the end of the study.
* females must be either surgically sterile, 2 years post-menopausal, or attest that they are using an acceptable method of contraception (including hormonal birth control, intrauterine device \[IUD\], double barrier methods, or vasectomized partner).
* females of childbearing potential must have urine pregnancy test (human chorionic gonadotropin \[HCG\]) that is negative at Baseline.
* must be able to read the diaries in Russian.
Exclusion Criteria: - currently under a doctor's care and treatment for constipation.
* have current constipation episode for more than one week prior to randomization.
* history of chronic constipation due to any underlying cause (inflammatory bowel disease, etc.).
* history of more than 3 months of constipation in the past year.
* have severe abdominal pain as the predominant constipation symptom.
* had with bowel movement in 48 hours prior to randomization.
* have celiac disease or known gluten sensitivity.
* history of colorectal cancer, anal abscess, anal fistula, anal fissure, anal stenosis, gastric retention or obstruction, bowel resection, rectocele, or colostomy.
* have known renal or hepatic insufficiency.
* have gastrointestinal bleeding or acute infection.
* history of alcohol or drug abuse.
* history of psychiatric disorders.
* history of significant ongoing medical problems, including kidney disease, or are scheduled for surgical procedures.
* currently taking or have taken within 7 days of randomization a concomitant medication that causes constipation, including opiates, antidepressants, selective serotonin reuptake inhibitors (SSRIs), antimotility agents, and anticholinergics, etc.
* plan to use laxatives during the treatment period other than the study medication.
* have participated in an investigational clinical, surgical, drug or device study within the past 30 days. (Concurrent skin patch testing of cosmetic or suncare products is allowed.)
* pregnant or lactating.
* allergic to polyethylene glycol or maltodextrin.
* employed or have immediate family members employed by a company that manufactures laxative products.