What is the best approach to treat constipation in patients with gastroparesis?

Treatment of Constipation in Gastroparesis

Add a stimulant laxative such as bisacodyl 10-15 mg orally 2-3 times daily, with a goal of one non-forced bowel movement every 1-2 days, and consider adding metoclopramide 10-20 mg every 6-8 hours to address the underlying gastroparesis-related dysmotility. 1, 2

Initial Assessment and Exclusion of Complications

Before initiating or escalating laxative therapy, perform a digital rectal examination to rule out fecal impaction, which is a common pitfall in patients with severe dysmotility. 2

• If impaction is present, treat first with glycerin suppositories, rectal bisacodyl, or manual disimpaction before starting maintenance therapy. 1, 2
• Rule out secondary causes including hypercalcemia, hypokalemia, hypothyroidism, diabetes mellitus, and mechanical obstruction, as these require specific interventions beyond standard constipation management. 1, 2

First-Line Pharmacologic Management

Add bisacodyl 10-15 mg orally 2-3 times daily as the primary stimulant laxative. 1, 2 This recommendation comes from the National Comprehensive Cancer Network guidelines and is specifically endorsed for refractory constipation in patients with complex motility disorders. 2

• Bisacodyl increases bowel motility through direct stimulation of colonic peristalsis, which is particularly important in gastroparesis patients who have generalized GI dysmotility. 1
• The goal is one non-forced bowel movement every 1-2 days, not daily bowel movements, which may be unrealistic in severe dysmotility. 1, 2

Addressing the Underlying Gastroparesis Component

Consider adding metoclopramide 10-20 mg every 6-8 hours if gastroparesis or severe dysmotility is suspected as a contributing factor. 1, 2 This prokinetic agent addresses the root cause of delayed transit throughout the GI tract, not just the colon. 3

• Metoclopramide is the only FDA-approved prokinetic for gastroparesis and works by enhancing gastric and intestinal motility. 3, 4
• This dual approach—stimulant laxative plus prokinetic—targets both colonic inertia and upper GI dysmotility that characterizes gastroparesis. 1, 2

Escalation Strategy if Initial Therapy Fails

If constipation persists despite bisacodyl and metoclopramide, add osmotic laxatives such as polyethylene glycol, lactulose, magnesium hydroxide, or magnesium citrate. 1

• Rectal bisacodyl suppositories 2 times daily can be used for more immediate relief. 1
• Prucalopride 2 mg once daily is an FDA-approved option for chronic idiopathic constipation that works as a selective 5-HT4 receptor agonist to stimulate colonic peristalsis and high-amplitude propagating contractions. 5 While not specifically studied in gastroparesis, its mechanism of action makes it a rational choice when standard therapies fail. 5

Critical Pitfalls to Avoid

Do not use bulk-forming fiber supplements in gastroparesis patients with constipation, as these can worsen gastric retention and potentially form bezoars in the setting of delayed gastric emptying. 3, 6

• Avoid anticholinergic antiemetics (such as promethazine or scopolamine) for nausea management in these patients, as they will worsen constipation. 1
• Monitor for medication-induced constipation from other agents commonly used in gastroparesis, including opioid analgesics for pain and ondansetron for nausea, both of which significantly worsen constipation. 1

Dietary and Supportive Measures

Encourage increased fluid intake and physical activity when appropriate, though recognize these measures alone are insufficient in gastroparesis-related constipation. 1

• Patients with gastroparesis should follow a low-fiber, low-fat diet with small frequent meals, which paradoxically may worsen constipation but is necessary for gastric symptom control. 1, 3
• In severe cases requiring jejunostomy tube feeding, ensure adequate hydration is delivered enterally to prevent dehydration-related constipation. 7

When Medical Management Fails

If constipation remains refractory to maximal medical therapy, consider methylnaltrexone 0.15 mg/kg subcutaneously every other day (maximum once daily) if opioid-induced constipation is a contributing factor. 1 This peripherally acting opioid antagonist relieves constipation without reversing analgesia. 1

• Venting gastrostomy may be needed in severe gastroparesis to decompress the stomach, though this addresses gastroparesis symptoms rather than constipation directly. 3
• Surgical options such as pyloroplasty should be reserved for carefully selected patients with refractory gastroparesis, but these do not specifically address constipation. 3