A 65-year-old client with chronic cancer pain has been started on long-acting morphine ER 30 mg PO every 12 hours with immediate-release morphine 10 mg every 4 hours as needed for breakthrough pain. Which scheduled intervention does the nurse anticipate to prevent the most common adverse effect?

Opioid-induced constipation (OIC) is the most common side effect of opioid therapy, occurs in nearly all patients, does not improve with tolerance, and is the leading reason patients abandon opioid analgesia. Mechanism: mu-receptor activation in the gut decreases peristalsis, increases sphincter tone, and decreases secretions. Standard prophylaxis from day one of opioid initiation: (1) stimulant laxative — senna 17.2 mg or bisacodyl 10 mg PO at bedtime — addresses decreased peristalsis, (2) stool softener — docusate 100 mg PO twice daily — alone is insufficient but added to a stimulant; some institutions omit docusate as evidence is mixed, (3) increase oral fluids to at least 2 L/day if not contraindicated, (4) increase dietary fiber gradually unless impaction risk, (5) activity, ambulation, abdominal massage. Escalate: osmotic laxative (polyethylene glycol, lactulose), enemas for impaction, peripheral mu-antagonist (methylnaltrexone, naloxegol, naldemedine) for refractory OIC. Diphenhydramine alone, fluid restriction, and bedrest are wrong. Bulk-forming laxatives (psyllium) are typically avoided in OIC because they require fluid and motility.

OIC prevention starts on day 1 with stimulant laxative plus optional softener plus fluids/fiber/activity. Tolerance never develops to constipation — it is a permanent side effect that must be actively prevented.