Amitiza (Lubiprostone) for IBS-C and Chronic Constipation After Laxative Failure
For adults with IBS-C or chronic constipation who have failed two laxatives, Amitiza (lubiprostone) is the appropriate choice over Movantik (naloxegol), as Movantik is specifically FDA-approved only for opioid-induced constipation in patients on chronic opioid therapy, not for IBS-C or chronic idiopathic constipation. 1
Why Amitiza Is the Correct Choice
FDA-Approved Indications
- Lubiprostone (Amitiza) is FDA-approved for both chronic idiopathic constipation (24 μg twice daily) and IBS-C in women aged 18 years or older (8 μg twice daily). 2, 3
- Naloxegol (Movantik) is FDA-approved exclusively for opioid-induced constipation in adults with chronic noncancer pain and has no indication for IBS-C or chronic constipation unrelated to opioids. 1
Guideline-Based Treatment Algorithm Position
- The 2023 AGA-ACG guidelines conditionally recommend lubiprostone as a second-line prescription option for chronic idiopathic constipation after failure of over-the-counter therapies like PEG, magnesium oxide, and stimulant laxatives. 4, 5
- Lubiprostone is positioned alongside other secretagogues (linaclotide, plecanatide) and prokinetics (prucalopride) as appropriate escalation therapy. 6, 4
Mechanism and Efficacy
How Lubiprostone Works
- Lubiprostone is a locally acting, highly selective type-2 chloride channel activator that promotes intestinal fluid secretion without stimulating gastrointestinal smooth muscle. 2, 7
- It increases liquid content of stool and accelerates both small bowel and colonic transit. 2
Evidence of Effectiveness
- Multiple trials demonstrate lubiprostone significantly increases weekly spontaneous complete bowel movements (SCBM) and improves stool consistency, straining, and constipation severity in both short- and long-term studies. 2, 8
- For IBS-C specifically, lubiprostone shows beneficial effects on global symptoms, abdominal pain, constipation-related symptoms, and overall quality of life. 2, 3
- After 1-2 months of treatment, lubiprostone demonstrates significantly greater improvements in mean abdominal discomfort/pain scores compared to placebo. 9
Dosing Strategy
IBS-C Dosing
- Start with 8 μg twice daily for IBS-C patients. 3, 7, 9
- This lower dose demonstrates the optimal combination of efficacy and safety for IBS-C. 9
Chronic Constipation Dosing
- Use 24 μg twice daily for chronic idiopathic constipation. 2, 7
- Current product labeling supports this dose differentiation based on the specific diagnosis. 7
Side Effect Management
Common Adverse Events
- The most common side effects are nausea, headache, and diarrhea, which are generally well-tolerated and mostly benign. 2, 8, 3
- Nausea risk is dose-dependent and significantly reduced when lubiprostone is taken with food and water. 5
- Higher doses (48 μg/day) are associated with more gastrointestinal adverse events, particularly diarrhea and nausea. 9
Safety Profile
- Lubiprostone has little systemic absorption and is almost free of any serious adverse effects. 7
- There is no evidence of rebound constipation or IBS symptoms following cessation of lubiprostone. 2
- It does not interact with antiepileptic medications, making it suitable for patients with seizure disorders. 5
Critical Pitfalls to Avoid
Wrong Drug for Wrong Indication
- Never use naloxegol (Movantik) or other peripherally acting mu-opioid receptor antagonists (PAMORAs) unless the patient is specifically on chronic opioid therapy. 1, 4, 5
- These agents will not provide benefit in non-opioid-related constipation and represent inappropriate prescribing. 1
Dosing Errors
- Do not use the 24 μg twice daily dose for IBS-C patients initially, as the 8 μg twice daily dose has better tolerability with equivalent efficacy for IBS-C. 3, 9
- Avoid starting at higher doses without first assessing tolerance at the recommended starting dose. 9
Administration Timing
- Always instruct patients to take lubiprostone with food and water to minimize nausea. 5