Efficacy and Safety of Polyethylene Glycol 3350 (PEG 3350) for Relief of Constipation (MK-8114-005)

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.