What is the recommended dosing schedule for Amitiza (lubiprostone) for chronic idiopathic constipation or opioid‑induced constipation, including adjustments for hepatic impairment?

Amitiza (Lubiprostone) Dosing

For chronic idiopathic constipation (CIC) and opioid-induced constipation (OIC), the standard dose is 24 mcg twice daily with food and water; for irritable bowel syndrome with constipation (IBS-C) in women, use 8 mcg twice daily. 1

Standard Dosing by Indication

Chronic Idiopathic Constipation (CIC)

• 24 mcg twice daily with food and water 1
• This dosing is supported by guideline recommendations 2
• Swallow capsules whole; do not break apart or chew 1

Opioid-Induced Constipation (OIC)

• 24 mcg twice daily with food and water 1
• Important limitation: Effectiveness has NOT been established in patients taking diphenylheptane opioids (e.g., methadone) 1, 3
• Indicated only for adult patients with chronic, non-cancer pain (including those with chronic pain related to prior cancer or its treatment who do not require frequent opioid dose escalation) 1

Irritable Bowel Syndrome with Constipation (IBS-C)

• 8 mcg twice daily with food and water 1
• FDA-approved only for women ≥18 years old 1

Hepatic Impairment Dosing Adjustments

Severe hepatic impairment (Child-Pugh Class C):

• CIC: 16 mcg twice daily (can increase to 24 mcg twice daily if tolerated and needed)
• OIC: 16 mcg twice daily (can increase to 24 mcg twice daily if tolerated and needed)
• IBS-C: 8 mcg once daily (can increase to 8 mcg twice daily if tolerated and needed)

Moderate hepatic impairment (Child-Pugh Class B):

• CIC: 16 mcg twice daily (can increase to 24 mcg twice daily if tolerated and needed)
• OIC: 16 mcg twice daily (can increase to 24 mcg twice daily if tolerated and needed)
• IBS-C: No adjustment needed

Mild hepatic impairment (Child-Pugh Class A):

• No dosing adjustment required for any indication 1

The rationale for these adjustments is that patients with moderate and severe hepatic impairment experience markedly higher systemic exposure of the active metabolite M3, with increased incidence and severity of adverse events correlating with greater hepatic impairment 1.

Administration Instructions

• Always take with food and water to reduce nausea 1
• Swallow capsules whole—do not break apart or chew 1
• Periodically assess the need for continuous therapy 1

Key Safety Considerations

Common adverse events (>4%):

• Nausea (most common—can be mitigated by taking with food) 1
• Diarrhea 1
• Headache, abdominal pain, abdominal distension, flatulence 1

Important warnings:

• Contraindicated in patients with known or suspected mechanical gastrointestinal obstruction 1
• Instruct patients to discontinue and contact provider if severe diarrhea occurs 1
• May cause syncope/hypotension or dyspnea (typically within first hour of first dose) 1

Clinical Context

Lubiprostone is positioned as a prescription option after traditional laxatives in the treatment algorithm. For CIC, guidelines list it alongside other intestinal secretagogues (linaclotide, plecanatide) as effective options 2. For OIC, guidelines recommend traditional laxatives as first-line agents, with lubiprostone considered when laxatives are insufficient, though formal guideline recommendations are limited due to evidence gaps 4. The drug works by activating chloride channel type 2 in the gut, increasing intestinal fluid secretion 2.