An 86-year-old woman with metastatic bowel cancer reports abdominal bloating; which laxative choice is least appropriate to prescribe for suspected opioid-induced constipation?

• A. Ispaghula husk
• B. Lactulose
• C. Docusate
• D. Senna

Answer: (A)

Opioid-induced constipation happens because opioids slow gut movement. In a patient with metastatic bowel cancer who has abdominal bloating, there’s a real risk of partial obstruction or severely reduced gut motility. Bulk-forming laxatives like ispaghula husk need adequate intestinal activity and plenty of fluids to work; if the bowel is sluggish or obstructed, they can accumulate bulk and worsen distension or even cause an impaction. So, they’re not appropriate here.

By contrast, stimulant laxatives (which directly stimulate bowel movements) and osmotic/softening agents are more suitable for opioid-induced constipation. Senna is a stimulant that helps propel stool, lactulose provides an osmotic pull to soften and move stool, and docusate acts as a stool softener to ease passage. In this clinical context, those options are preferred over a bulk-forming laxative.