What are the treatment options for medication-induced constipation in patients with Parkinson's disease?

Treatment for Parkinson's Medication-Induced Constipation

For Parkinson's disease patients with medication-induced constipation, a combination approach using probiotics with prebiotic fiber, increased fluid and dietary fiber intake, and osmotic or stimulant laxatives is recommended as first-line treatment. 1

Understanding Constipation in Parkinson's Disease

Constipation in Parkinson's disease has multiple causes:

• Neurodegenerative processes affecting the enteric nervous system 1
• Side effects of PD medications, particularly dopamine agonists and anticholinergics 1
• Reduced physical activity due to motor impairment 1
• Pelvic floor dyssynergia 1

Notably, dopaminergic medications (levodopa and dopamine agonists) have been associated with increased risk of constipation, with an odds ratio of 2.287 for levodopa and 1.805 for dopamine agonists 2.

First-Line Treatment Approach

Non-Pharmacological Interventions

• Increase fluid intake to improve colonic transit 1
• Increase dietary fiber intake if adequate fluid intake and physical activity are possible 1
• Encourage physical activity when appropriate 1, 3
• Daily consumption of fermented milk containing probiotics and prebiotic fiber (shown in a large RCT with 120 patients to increase complete bowel movements, improve stool consistency, and reduce laxative use) 1

Pharmacological Interventions

First-Line Medications

• Polyethylene glycol (PEG): 17g with 8 oz water twice daily 1, 3

  • Has shown durable response over 6 months 1
  • Can be used after or in combination with fiber supplements 1
  • Side effects include abdominal distension, loose stool, flatulence, and nausea 1

• Stimulant laxatives: 1

  • Bisacodyl 10-15 mg daily to TID with a goal of one non-forced bowel movement every 1-2 days 1
  • Senna (start at lower dose and increase if needed) 1

Second-Line Treatment Options

For patients who fail to respond to first-line treatments:

• Magnesium oxide (start at lower dose and increase if necessary) 1

  • Avoid in patients with renal insufficiency due to risk of hypermagnesemia 1

• Lactulose for patients who fail or are intolerant to OTC therapies 1

  • Note that bloating and flatulence are common dose-dependent side effects 1

• Consider adding a prokinetic agent (e.g., metoclopramide 10-20 mg PO QID) for severe cases 1

Treatment Algorithm for Refractory Cases

For patients with persistent constipation despite above measures:

1. Rule out impaction or obstruction (physical exam, abdominal x-ray) 1
2. Consider glycerine suppository or mineral oil retention enema 1
3. For severe cases, consider methylnaltrexone 0.15 mg/kg subcutaneously every other day (except in cases of post-op ileus and mechanical bowel obstruction) 1, 3

Important Clinical Considerations

• Beta-blockers have been associated with a lower risk of constipation in PD patients (OR 0.293), which is an unexpected finding that may be considered in patients with comorbid conditions requiring beta-blockers 2

• Lubiprostone has shown benefit for constipation due to slow colonic transit in PD according to evidence-based medicine guidelines 4

• For constipation secondary to defecatory dysfunction due to pelvic floor dyssynergia, consider levodopa timing adjustments, apomorphine injections, or botulinum toxin type A injection into the puborectalis muscle 4

• Constipation in PD may be more complex than decreased stool frequency alone - patients may experience multiple partially complete bowel movements 5

Common Pitfalls to Avoid

• Using stool softeners alone without stimulant laxatives is not recommended 3
• Failing to provide prophylactic treatment from the start of therapy with constipation-inducing medications 3
• Overlooking that constipation may affect absorption of oral PD medications, potentially requiring dose adjustments 6
• Ignoring that constipation in PD often involves both slow transit and defecatory dysfunction, which may require different treatment approaches 7