Table 2.

Inclusion and exclusion criteria.

Inclusion criteria
Age, 20 years and older
Colonic evaluation (colonoscopy or barium enema) within the previous 5 years or regular followup at gastrointestinal clinic
Chronic constipation confirmed by at least one of the following three criteria:
Meeting Rome III criteria of constipation
Receiving enema, suppository, or digital maneuver at least once a week in the past three months
Laxative use in more than half time of the last three months
Exclusion criteria
Known cause of colorectal obstruction or structural lesions (e.g., intestinal neoplasm, anal abscess, anal fistula, anal fissure, rectocele, and megacolon)
Inflammatory bowel disease
Irritable bowel syndrome
Hypothyroidism
Spinal cord injury
Muscular dystrophy
Known severe hepatic or renal insufficiency (e.g., liver cirrhosis or receiving hemodialysis)
Unknown cause of gastrointestinal bleeding or acute infection
Exposure to any other investigational drug within 30 days prior to enrollment
History of allergy to the composition of the study medication
New onset or unstable psychiatric disorders
Pregnancy or breastfeeding
History of alcohol or drug abuse
Any condition associated with poor compliance with medical treatment