Constipation in Cancer Treatment: Is It Common and How To Manage It

Constipation is fairly common during cancer treatment, often due to chemotherapy and medications used for pain or nausea. ^[1] Some people notice stools become hard, small, difficult to pass, or less frequent than usual. ^[2] Constipation can be influenced by diet, activity level, and lifestyle, and certain chemotherapy drugs and opioids (pain medicines) can make it worse. ^[2] [PM14]

Why Constipation Happens

• Medications (especially opioids and anti‑nausea drugs): Opioids slow bowel movement and can lead to opioid‑induced constipation. [PM14] This effect is a well‑recognized problem in cancer care. [PM13]
• Chemotherapy effects: Some chemotherapy agents can directly cause constipation. ^[1]
• Diet and activity changes: Lower fiber intake, dehydration, and reduced physical activity during treatment contribute to hard or infrequent stools. ^[2]

First‑Line Self‑Care Strategies

• Increase fiber gradually: Fruits, vegetables, whole grains, beans, nuts, and seeds add bulk and help stools move. ^[2]
• Hydrate well: Aim for about 8 glasses (about 240 ml each) of liquids daily if your care team says it’s safe; warm beverages can help trigger bowel movements. ^{[1] [3]}
• Gentle activity: Short walks or light exercise can stimulate the bowel. ^[1]
• Routine helps: Eating meals at regular times can support bowel rhythm. ^[3]

Over‑the‑Counter Options

• Stool softeners (e.g., docusate): These can make stools easier to pass but may be less effective alone if stools are very hard. ^[4]
• Osmotic laxatives (e.g., polyethylene glycol/PEG): Draw water into the bowel to soften stools; evidence supports PEG as an effective first‑line option for constipation when lifestyle changes aren’t enough. [PM18]
• Stimulant laxatives (e.g., senna, bisacodyl): Increase bowel muscle activity and can be useful, especially with opioid‑related constipation. [PM18]

It’s generally advisable to start with an osmotic laxative (like PEG) and add a stimulant if needed, based on your care team’s guidance. [PM18]

When Opioids Are Involved

Constipation from opioids is common and often needs proactive treatment. [PM14] Many cancer care teams recommend starting a bowel regimen (typically an osmotic plus a stimulant laxative) at the same time as an opioid. [PM13] If standard laxatives do not work, peripherally acting mu‑opioid receptor antagonists (PAMORAs) such as naloxegol or methylnaltrexone can be considered to specifically counter opioid effects in the gut. [PM16] These medicines require clinical oversight to ensure safety and fit with your overall treatment plan. [PM13]

Practical Daily Tips

• Set a regular bathroom time: A daily routine after meals can help train the bowel. ^[3]
• Don’t ignore the urge: Responding promptly can prevent worsening constipation. ^[2]
• Monitor your pattern: Track frequency, stool form, and any straining to share with your care team. [PM14]
• Avoid excessive straining: If stools are very hard, increase fluids and consider PEG; ask your clinician before using enemas or suppositories. [PM18]

Red Flags: When to Call Your Care Team

• No bowel movement for several days despite laxatives and lifestyle changes. ^[5]
• Severe abdominal pain, vomiting, or swelling (could signal blockage). ^[5]
• Blood in stool or sudden change in bowel habits that doesn’t improve. ^[5]
• You are starting or increasing opioids and have a history of constipation early prevention is recommended. [PM14]

Diet Guide for Constipation During Treatment

• Increase: Prunes/prune juice, pears, berries, leafy greens, whole grains, beans, oats, nuts, seeds; drink adequate fluids. ^{[1] [2]}
• Consider limiting (if worsening constipation): Low‑fiber processed foods and excessive cheese; balance iron‑rich foods with fiber to offset hard stools. ^[2]

Summary

Constipation is a common side effect during cancer care, especially with chemotherapy and pain or anti‑nausea medicines. ^{[1] [2]} Managing it typically involves fiber, fluids, gentle activity, and timely use of laxatives, with PEG and stimulant laxatives often forming the backbone of treatment. [PM18] For opioid‑related constipation, starting a bowel regimen early is helpful, and PAMORAs may be used if standard measures fail under clinical supervision. [PM13] [PM16]

Quick Comparison: Constipation Strategies

Approach	How it helps	Typical use	Notes
Fiber + Fluids	Softens and bulks stool	First step for many	Increase gradually to avoid gas. [2]
Gentle Activity	Stimulates bowel movement	Daily walks	Adjust to energy level. [1]
PEG (osmotic)	Pulls water into stool	First‑line OTC	Strong evidence for efficacy. [PM18]
Stimulants (senna/bisacodyl)	Increases bowel motility	Add‑on or short‑term	Useful in opioid constipation. [PM18]
Stool softeners (docusate)	Softens stool surface	Mild cases	Often combined with other agents. [4]
PAMORAs (e.g., naloxegol, methylnaltrexone)	Blocks opioid effect in gut	Refractory OIC	Prescription; monitor closely. [PM16] [PM13]

If you’re unsure which option is right for you, share your current medicines, bowel pattern, and any previous laxatives with your care team so they can tailor a plan. [PM14]