What is the dosing of Amitiza (lubiprostone) for constipation?

Dosing of Amitiza (Lubiprostone) for Constipation

The recommended dosage of Amitiza (lubiprostone) for chronic idiopathic constipation in adults is 24 mcg twice daily taken with food and water. 1

Dosing Guidelines by Indication

Chronic Idiopathic Constipation (CIC)

• Standard dose: 24 mcg twice daily with food and water 2, 1
• Duration: No specific time limit in drug labeling, though clinical trials were 4 weeks 2

Irritable Bowel Syndrome with Constipation (IBS-C)

• Lower dose: 8 mcg twice daily with food and water 1, 2
• For women ≥18 years only 1

Opioid-Induced Constipation (OIC)

• Standard dose: 24 mcg twice daily with food and water 1
• For adult patients with chronic non-cancer pain 2, 1
• Note: Not established for effectiveness in patients taking diphenylheptane opioids (e.g., methadone) 1

Dosage Adjustments for Special Populations

Hepatic Impairment

• Moderate impairment (Child-Pugh Class B):
  • For CIC/OIC: Reduce to 16 mcg twice daily 1
  • For IBS-C: No adjustment necessary 1
• Severe impairment (Child-Pugh Class C):
  • For CIC/OIC: Reduce to 8 mcg twice daily 1
  • For IBS-C: Reduce to 8 mcg once daily 1

Administration Guidelines

• Take with food and water to reduce nausea 2, 1
• Swallow capsules whole (do not break apart or chew) 1
• Capsules are available as 8 mcg (pink, printed with "SPI" on one side) 1

Efficacy and Mechanism of Action

• Lubiprostone is a chloride channel activator that increases intestinal fluid secretion and accelerates GI transit 2
• Effects typically manifest within 2 days in responsive patients 2
• Increases spontaneous bowel movements by approximately 2 per week compared to placebo 2
• Improves stool consistency and reduces straining 2, 3

Common Side Effects and Management

• Nausea (occurs in up to 35% of patients) 2, 1
  • Risk is dose-dependent
  • Taking with food and water reduces incidence 2
  • Usually mild to moderate; leads to discontinuation in only about 5% of patients 2
• Diarrhea 1
  • Discontinue if severe diarrhea occurs
• Syncope and hypotension (rare) 1
  • More common with 24 mcg twice daily dosing
  • Can occur within an hour after taking first or subsequent doses
  • Risk increases with concomitant diarrhea or vomiting

Clinical Pearls

• Contraindicated in patients with known or suspected mechanical gastrointestinal obstruction 1
• Has negligible systemic absorption 2
• Efficacy in elderly (≥65 years) is comparable to the overall population 2
• Periodically reassess the need for continued therapy 1
• Should be taken with meals to minimize nausea 2, 1

Lubiprostone offers an effective pharmacologic option for chronic constipation when over-the-counter agents are ineffective, with the American Gastroenterological Association suggesting its use in adults with chronic idiopathic constipation who don't respond to OTC agents 2.