Understanding if Rituximab Can Cause Constipation and How to Manage It

October 10, 2025 •

4 min read

According to sources like Versus Arthritis and Memorial Sloan Kettering Cancer Center, constipation is a reported side effect of rituximab treatment. While not always the primary cause, this medication can contribute to bowel irregularity, sometimes in combination with other concurrent therapies like chemotherapy.

Quick Summary

Rituximab can cause constipation, a side effect sometimes exacerbated by other medications like anti-nausea drugs or chemotherapy. Effective management involves lifestyle changes such as increased fiber and fluids, with over-the-counter laxatives or medical intervention needed for more severe cases. Patients should monitor for serious complications like bowel blockages.

Key Points

Possible Side Effect: Constipation is listed as a potential, though not universal, side effect of rituximab therapy.
Risk Factors: The risk of constipation can be increased by concurrent use of other chemotherapy drugs, certain anti-nausea medications, or general changes in diet and activity.
Management: Initial steps to manage constipation include increasing fiber and fluid intake, along with incorporating gentle exercise.
Laxatives: Over-the-counter laxatives and stool softeners can be used, but only after consultation with a healthcare provider.
Red Flag Symptoms: Seek immediate medical attention if you experience severe abdominal pain, persistent vomiting, or bloody stools, as this could indicate a more serious bowel issue.
Communication is Key: Always inform your doctor or healthcare team about any changes in bowel habits during your treatment course.

Can Rituximab Cause Constipation?

Yes, rituximab can cause constipation. It is listed as a potential side effect on drug information pages from several reputable healthcare institutions. The likelihood and severity of this issue can vary from person to person. For some, it might be a mild and infrequent issue, while for others, it can be more persistent and bothersome. It is important to consider rituximab's role within the larger context of a patient's overall treatment plan, as other factors and medications are often involved.

Factors Contributing to Constipation During Rituximab Therapy

While rituximab itself can affect the digestive system, it is important to understand that constipation during treatment is often multifactorial. Several other elements can increase or contribute to the risk:

Combination Therapy with Chemotherapy

Rituximab is frequently used in combination with other chemotherapy drugs, especially for conditions like non-Hodgkin's lymphoma. Certain chemotherapy agents are known to cause gastrointestinal issues, including constipation, due to their effect on the body's cells, including those in the intestinal lining. In these cases, the combined effect of the medications can heighten the risk of constipation or other serious bowel problems. Memorial Sloan Kettering Cancer Center notes that serious bowel problems, including blockages or tears, have occurred in people taking rituximab with some cancer drugs.

Anti-Nausea Medication

To combat the potential for nausea and vomiting associated with rituximab infusions, anti-nausea medicines are often administered concurrently. Certain anti-nausea drugs can cause constipation as a side effect, contributing to the problem.

Changes in Diet and Activity

Cancer treatment in general can lead to changes in a person's routine, diet, and activity levels. Reduced physical activity and shifts in eating habits, such as decreased fiber intake due to appetite changes, are common factors that can lead to constipation.

Underlying Medical Conditions

Pre-existing conditions, particularly in cancer patients, can also play a role. Issues like inflammatory bowel disease (IBD) or other gastrointestinal disorders may be exacerbated by treatment. Rituximab can cause a rare form of colitis in some individuals.

Management Strategies for Rituximab-Related Constipation

If you experience constipation while on rituximab, several strategies can provide relief. It is crucial to discuss all management options with a healthcare provider, particularly before starting new medications.

Lifestyle Adjustments:

Increase fiber intake by eating more whole grains, fruits, and vegetables.
Ensure adequate fluid intake, aiming for at least eight glasses of water daily. Warm beverages may also help.
Engage in gentle, regular exercise, such as walking, to stimulate bowel movements.

Over-the-Counter Laxatives (Consult Your Doctor First):

Osmotic Laxatives: These work by drawing water into the bowel to soften the stool, such as polyethylene glycol (MiraLAX).
Stool Softeners: Products like docusate sodium (Colace) help mix fluid into the stool, making it easier to pass.
Stimulant Laxatives: These speed up muscle movement in the colon. They are typically used for short-term relief, but may cause cramping.

When to Seek Immediate Medical Attention: While most cases are mild, some symptoms indicate a more serious issue that requires urgent care. Contact your healthcare provider immediately if you experience:

Very bad stomach pain
Very severe constipation
Repeated vomiting
Blood in your stool

Comparing Rituximab and Other Treatments

It's useful to understand how constipation with rituximab compares to other treatments. The risk and severity can differ, especially when rituximab is used in combination with other potent drugs.


Treatment Context	Typical Frequency of Constipation	Severity of Constipation	Key Considerations
Rituximab Monotherapy	Can be a less common, but reported side effect.	Usually mild and manageable through conservative measures.	Focus on lifestyle factors like diet and hydration.
Rituximab + Chemotherapy	The risk is often higher and more frequent due to the combined effect of medications.	Can range from mild to severe, and is associated with a risk of serious bowel problems.	Close monitoring for severe abdominal pain or other serious symptoms is essential.
Rituximab + Anti-emetics	Increased risk due to the potential constipating effects of some anti-nausea medications.	Typically mild to moderate, manageable by adjusting the type or dosage of anti-emetics.	Inquire about different anti-nausea medication options if constipation is a primary concern.
Opioid Pain Medication	Very high risk, as opioids directly slow down intestinal movement.	Often severe and requires a proactive management protocol with stimulant and osmotic laxatives.	Constipation is a expected side effect requiring daily laxatives, not just diet changes.
Other Immunotherapies	Can vary widely. Some immunotherapies also list constipation as a side effect.	Dependent on the specific drug and individual patient response.	Requires careful patient-specific management strategies.

Conclusion: Navigating Constipation with Rituximab

Constipation is a recognized and manageable side effect of rituximab, though its occurrence and severity are often influenced by other factors, such as concomitant chemotherapy or anti-nausea drugs. Patients should proactively discuss their bowel habits with their healthcare team to prevent and address issues early on. Simple lifestyle changes, such as increasing fiber and fluid intake, can be effective. When these measures are insufficient, over-the-counter laxatives, used under a doctor's guidance, can provide relief. Patients receiving rituximab in combination with chemotherapy should be vigilant for signs of more serious gastrointestinal problems, like severe abdominal pain or bloody stool, and report them immediately. Open communication with your healthcare provider ensures that this and other side effects are managed effectively, helping to maintain your quality of life during treatment. For more comprehensive information on side effects, you can visit the Rituxan (rituximab) information pages on the official website or trusted sources like Drugs.com.

Frequently Asked Questions

Constipation is a reported side effect, but its frequency can vary. It may be more common when rituximab is used alongside chemotherapy agents known to cause gastrointestinal issues or with specific anti-nausea drugs.

Commonly used laxatives include osmotic laxatives (like MiraLAX) and stool softeners (like Colace). However, you must consult your healthcare provider before taking any new medication, as certain types might be contraindicated depending on your overall health.

You should check with your doctor before using bulk-forming laxatives, especially if your fluid intake is limited. Some experts do not recommend them for medication-related constipation, as they may not be effective and could potentially cause problems if insufficient fluids are consumed.

You should call your healthcare provider if you have not had a bowel movement for three days, experience severe abdominal pain, repeated vomiting, or notice blood in your stool.

Yes, increasing dietary fiber through whole grains, fruits, and vegetables, along with drinking plenty of water, can help manage constipation. However, for drug-induced constipation, these changes alone may not be sufficient.

In rare instances, particularly when combined with certain chemotherapy drugs, rituximab has been associated with serious gastrointestinal issues like bowel obstruction or perforation. Any severe, worsening stomach pain should be reported to your doctor immediately.

The duration of constipation can vary. Often, it improves with lifestyle modifications and laxatives. For some, bowel issues may persist for as long as they are receiving treatment, while for others, it may only occur in the days following an infusion.