Constipation in Colorectal Cancer Treatment: Is it common and how to manage it?

Yes, constipation is quite common during colorectal cancer treatment, and it can stem from chemotherapy drugs, pain medicines (especially opioids), reduced activity, dehydration, and dietary changes. ^[1] Constipation generally means fewer bowel movements than usual, hard stools, or difficulty passing stool. ^[1]

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Why constipation happens

• Chemotherapy effects: Some chemotherapy agents can slow bowel movement, leading to hard or infrequent stools. ^[1]
• Pain and nausea medicines: Opioids and certain anti‑nausea drugs commonly cause constipation by slowing gut motility and reducing secretions. ^[1]
• Lifestyle factors during treatment: Less physical activity, lower fluid intake, and reduced fiber can further contribute. ^[2]

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First-line self-care

• Increase fiber gradually: Aim to eat more fruits, vegetables, whole grains, beans, nuts, and seeds to soften and bulk the stool. ^[1] Drinking warm liquids, like tea, can help trigger a bowel movement. ^[2]
• Hydrate well: Try to drink at least 8–10 cups of fluids daily, if your care team has not set fluid limits for you. ^[2]
• Gentle activity: Short walks or light exercise can stimulate bowel function. ^[1]
• Routine helps: Try going to the bathroom at the same time each day; respond promptly to the urge to go. ^[3]

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Safe over‑the‑counter options

• Stool softeners (e.g., docusate): These can make stool easier to pass, especially when stools are very hard. ^[4]
• Stimulant laxatives (e.g., senna, bisacodyl): These encourage bowel movement and are often effective for medication‑induced constipation. Your care team can advise on dosing. ^[5]
• Osmotic agents (e.g., polyethylene glycol/MiraLAX): These draw water into the bowel to soften stool and can be used regularly if needed. ^[6]

It’s reasonable to combine a stool softener with a stimulant laxative if one alone does not work, and to adjust doses under guidance from your clinician. ^[5]

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When opioids are involved

• Opioid-induced constipation (OIC): Opioids act on gut receptors to slow movement and increase sphincter tone, making constipation particularly persistent. Prevention with laxatives from day one of opioid therapy is usually recommended. [PM20]
• If standard laxatives don’t work: Peripherally acting mu‑opioid receptor antagonists (PAMORAs), such as naldemedine, naloxegol, or methylnaltrexone, can specifically counter opioid effects in the gut without affecting pain control. These are supported by good evidence for OIC. [PM20]

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Red flags: when to call your care team

• No bowel movement or no gas for more than 2–3 days should prompt a call. ^[5]
• Hard stools or difficulty passing stools lasting more than 2–3 days also warrant medical advice. ^[5]
• Severe abdominal pain, persistent vomiting, or sudden worsening can signal complications and should be reviewed urgently, especially during treatments that carry a small risk of gastrointestinal perforation. [PM17]

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Practical daily tips

• Eat at regular times to help your bowel develop a rhythm. ^[2]
• Use a footstool to elevate your feet on the toilet; this can ease stool passage.
• Privacy and unhurried time in the bathroom can reduce straining.
• Track bowel habits so you and your care team can adjust medicines early.

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Summary

Constipation is a frequent and expected side effect during colorectal cancer treatment due to chemotherapy, opioids, and lifestyle changes. Most people improve with fiber, fluids, activity, and appropriate use of stool softeners, stimulant laxatives, or osmotic agents; and those on opioids may need targeted medicines (PAMORAs) if standard measures fall short. ^{[1] [2]} [PM20] Seek medical advice if you go more than 2–3 days without a bowel movement or gas, or if symptoms are severe. ^[5]