The purpose of this study is to evaluate a daily dose of BLI400 Laxative for safety and efficacy versus lubiprostone in constipated adults.

Inclusion Criteria:

• Male or female subjects at least 18 years of age
• Constipated, defined by the following adapted ROME II definition:

A. Fewer than 3 spontaneous defecations per week and at least one of the following symptoms for at least 12 weeks (which need not be consecutive) in the preceding 12 months:

1. Straining during > 25% of defecations
2. Lumpy or hard stools in > 25% of defecations
3. Sensation of incomplete evacuation for > 25% of defecations

B. Loose stools are rarely present without the use of laxatives

C. There are insufficient criteria for IBS - loose (mushy) or watery stool in the absence of laxative use for more than 25% of bowel movements

Criteria A, B and C must be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.

• Otherwise in good health, as determined by physical exam and medical history
• If female, and of child-bearing potential, is using an acceptable form of birth control
• Negative urine pregnancy test at screening, if applicable
• In the Investigator's judgment, subject is mentally competent to provide informed consent to participate in the study

Exclusion Criteria:

• Subjects with known or suspected ileus, gastrointestinal obstruction, gastric retention, bowel perforation, toxic colitis, toxic megacolon
• Subjects who have had major surgery 30 days before Visit 1; appendectomy or cholecystectomy 60 days before Visit 1; abdominal, pelvic, or retroperitoneal surgery 6 months before Visit 1; bariatric surgery or surgery to remove a segment of the GI tract at any time before Visit 1
• Subjects with hypothyroidism that is being treated and for which the dose of thyroid hormone has not been stable for at least 6 weeks at the time of Visit 1
• Subjects taking laxatives, enemas or prokinetic agents that refuse to discontinue these treatments from Visit 1 until after completion of Visit 5
• Subjects who are pregnant or lactating, or intend to become pregnant during the study
• Subjects of childbearing potential who refuse a pregnancy test
• Subjects who are allergic to any study medication component
• Subjects taking narcotic analgesics or other medications known to cause constipation
• Subjects with clinically significant cardiac abnormalities identified at the Visit 1 ECG
• Subjects who, in the opinion of the Investigator, should not be included in the study for any reason, including inability to follow study procedures
• Subjects who have participated in an investigational clinical, surgical, drug, or device study within the past 30 days
• Subjects with an active history of drug or alcohol abuse
• Subjects have been hospitalized for a psychiatric condition or have made a suicide attempt during the 2 years before Visit 1
• Subjects who withdraw consent at any time prior to completion of Visit 1 procedures
• Subjects with known or suspected moderate to severe hepatic insufficiency (Child Pugh Classes B and C)