Opioid-Induced Constipation Management

Introduction to Opioid-Induced Constipation

Opioid-induced constipation (OIC) is a common and persistent side effect of opioid therapy that generally persists throughout treatment, as opioids bind to μ-receptors in the gastrointestinal tract, reducing peristalsis and intestinal secretions, and increasing fluid absorption from the bowel, resulting in harder, drier stools and delayed transit time, as reported by the National Comprehensive Cancer Network 1
The constipation potential of opioids varies, with morphine, hydrocodone, and codeine having significant constipation potential, while transdermal fentanyl has lower constipation rates than oral morphine, as recommended by the National Comprehensive Cancer Network 2

Preventive measures, including prophylactic stimulant laxative with or without stool softener, polyethylene glycol with adequate fluid intake, and maintaining physical activity as tolerated, should be implemented for all patients on opioids, according to the National Comprehensive Cancer Network 3, 1, 4, 5
Fiber supplements like psyllium are unlikely to control opioid-induced constipation and may worsen symptoms, as suggested by the National Comprehensive Cancer Network 1, 4
The National Comprehensive Cancer Network recommends a first-line approach of implementing preventive measures for all patients on opioids, including prophylactic stimulant laxative and adequate fluid intake 1

Methylnaltrexone typically produces a bowel movement within 30 minutes to 4 hours after administration, with most patients experiencing laxation within 90 minutes of receiving the medication, as reported by the American Society of Clinical Oncology and the European Society for Medical Oncology 6, 3
The median time to laxation is 0.8 hours versus 23.6 hours for placebo in fixed-dose studies, according to the American Society of Clinical Oncology 3
Within 4 hours, 48-62.9% of patients experience laxation after the first dose, with clinical evidence demonstrating a rapid onset of action, as reported by the European Society for Medical Oncology 3
Methylnaltrexone is a peripheral μ-opioid receptor antagonist that does not cross the blood-brain barrier, selectively antagonizes opioid receptors in the gastrointestinal tract, and preserves centrally mediated analgesic effects of opioids, as suggested by the American Society of Clinical Oncology and the European Society for Medical Oncology 3

The initial dosage is 0.15 mg/kg administered subcutaneously every other day, which may be increased to once daily if needed, as recommended by the European Society for Medical Oncology 3
For moderate to severe renal impairment, the dose should be reduced by 50%, as suggested by the National Comprehensive Cancer Network 1
Subcutaneous methylnaltrexone is recommended for opioid-induced constipation in patients with advanced illness when standard laxative therapy is insufficient, as recommended by the European Society for Medical Oncology 3

Most patients report abdominal cramping with methylnaltrexone use, as reported by the American College of Physicians 6
Common adverse effects of methylnaltrexone include abdominal pain (27.9%), flatulence (13.3%), and nausea (10.9%), which are generally mild to moderate in severity, as reported by the European Society for Medical Oncology 6, 3
Methylnaltrexone is contraindicated in patients with known or suspected mechanical gastrointestinal obstruction, as stated by the National Comprehensive Cancer Network 1, 7

The European Society for Medical Oncology recommends monitoring response to methylnaltrexone, assessing for laxation within 4 hours, and considering increasing frequency to once daily if inadequate response 3
If constipation develops despite preventive measures, rule out bowel obstruction or impaction, titrate laxatives with a goal of one non-forced bowel movement every 1-2 days, and consider adding osmotic laxatives (magnesium-based products, lactulose, polyethylene glycol), as suggested by the National Comprehensive Cancer Network 2, 7, 1
Patient satisfaction with bowel function is also improved with methylnaltrexone treatment, as suggested by the European Society for Medical Oncology 3
Methylnaltrexone treatment is associated with significant improvement in constipation-specific quality of life and reduced distress related to constipation, as reported by the European Society for Medical Oncology 3

Tapentadol, with its dual mechanism of action as a μ-opioid receptor agonist and norepinephrine reuptake inhibitor, offers a better profile with significantly lower rates of constipation compared to traditional μ-opioid receptor agonists like oxycodone or morphine, as advised by the National Comprehensive Cancer Network 1
Morphine, hydromorphone, hydrocodone, oxymorphone, and codeine should be used with caution in patients with fluctuating renal function due to potential accumulation of renally cleared metabolites, as advised by the National Comprehensive Cancer Network 1, 2, 4