Assessing Tenapanor as a Treatment of CF-related Constipation.

Inclusion criteria

• Having confirmed cystic fibrosis (either by sweat chloride or genetic testing)
• Meeting criteria for CFrC

Must include 2 of the following, with or without abdominal pain for at least 3 months, with symptom onset at least 6-months prior:

• Straining in at least 25% of defecations
• Bristol Stool Scale 1-2 more than 25% of defecations (change in stool form)
• Sensation of incomplete evacuation more than 25% of defecations
• Sensation of anorectal obstruction/blockage more than 25% of defecations
• Manual disimpaction/manipulation of pelvic floor to facilitate more than 25% of defecations
• Fewer than 3 spontaneous bowel movements weekly (change in stool frequency)
• Loose stools rarely present without the use of laxatives
• Willingness to avoid major dietary or lifestyle changes during study.

Exclusion criteria

• Use of any antibiotic to treat infection within the 4-weeks prior to study initiation (stable azithromycin dosed 3-times weekly for lung function is to be allowed)
• Inability to discontinue standing bowel regimen (including fiber, stool softener, as well as either osmotic or stimulant laxative, pro-kinetic serotonergic agents, or other therapy) 2-weeks prior to study drug initiation (with ability to use osmotic laxative therapy as rescue therapy only).
• Severe CFrC as determined by study team
• Prior tenapanor usage
• Hospitalization within 4-weeks prior to study initiation.
• DIOS within 4-weeks prior to study initiation.
• Other known/suspected mechanical obstruction