Can you take Miralax (polyethylene glycol) with Linzess (linaclotide)?

Taking Miralax with Linzess: Safety and Efficacy

Yes, you can safely take Miralax (polyethylene glycol) with Linzess (linaclotide) as they work through different mechanisms and can be used together for enhanced treatment of constipation. 1, 2

Mechanism of Action and Compatibility

These medications work through complementary mechanisms:

• Linzess (linaclotide): Acts as a guanylate cyclase-C agonist that increases intestinal fluid secretion and accelerates GI transit 2

  • Primarily works by elevating cyclic guanosine monophosphate (cGMP) levels 3
  • Reduces visceral hypersensitivity (pain perception) in addition to treating constipation 3

• Miralax (polyethylene glycol): Functions as an osmotic laxative that draws water into the intestinal lumen to soften stool and increase bowel movement frequency 4

Clinical Guidelines Supporting Combination Use

The American Gastroenterological Association-American College of Gastroenterology clinical practice guideline specifically mentions that prescription medications like Linzess "can be used as a replacement or as an adjunct to OTC agents" such as polyethylene glycol (Miralax) 1. This directly supports the combination use of these medications.

Additionally, the 2023 American College of Cardiology expert consensus decision pathway includes both polyethylene glycol and linaclotide in their list of recommended treatments for constipation, suggesting they are part of the therapeutic armamentarium that can be used together when needed 1.

Dosing Considerations

When using these medications together:

• Linzess: Take on an empty stomach at least 30 minutes before the first meal of the day 2

  • IBS-C: 290 mcg once daily
  • Chronic idiopathic constipation: 72 mcg or 145 mcg once daily

• Miralax: Typically 17g daily dissolved in 4-8 oz of water or other liquid 1, 4

  • Can be taken at any time of day, but avoid taking at the exact same time as Linzess

Potential Side Effects to Monitor

When combining these medications, be aware of:

1. Diarrhea: The most common side effect of both medications, particularly with Linzess (occurs in approximately 20% of patients) 2, 5

   • 90.5% of diarrhea cases with Linzess are mild to moderate in intensity 5
   • The risk of severe diarrhea may increase when combining with Miralax

2. Dehydration: Monitor for signs of dehydration, especially in elderly patients or those with comorbidities 2, 6

3. Abdominal discomfort: Both medications can cause abdominal pain, cramping, or bloating 1, 2

Clinical Decision Algorithm

1. For patients with chronic idiopathic constipation who have inadequate response to Miralax alone:

   • Add Linzess 72 mcg or 145 mcg once daily (starting with the lower dose to minimize diarrhea risk) 1, 2

2. For patients with IBS-C who have inadequate response to Miralax alone:

   • Add Linzess 290 mcg once daily 2

3. For patients already on Linzess with suboptimal response:

   • Add Miralax 17g daily as rescue therapy or for regular use 1

4. If excessive diarrhea occurs with combination therapy:

   • Consider reducing the Miralax dose or frequency while maintaining the Linzess dose
   • Alternatively, consider reducing Linzess to a lower dose if using the 145 mcg or 290 mcg dose

Special Considerations

• Elderly patients may be more susceptible to dehydration with combination therapy 2
• Both medications have minimal systemic absorption, reducing the risk of drug-drug interactions 2, 3
• Contraindicated in patients with known or suspected mechanical GI obstruction 2

The combination of Miralax and Linzess provides a rational approach to treating constipation by addressing the condition through different but complementary mechanisms, potentially improving outcomes for patients with refractory symptoms.