What are the steps to manage constipation induced by oxycodone (OxyContin) in a patient?

Management of Oxycodone-Induced Constipation

Start prophylactic laxatives immediately when initiating oxycodone—use a stimulant laxative (senna or bisacodyl) as first-line therapy, and escalate systematically through osmotic laxatives, then peripherally acting μ-opioid receptor antagonists (PAMORAs) for laxative-refractory cases. 1, 2

Step 1: Initial Assessment

Before starting treatment, perform these specific evaluations:

• Rule out mechanical obstruction, fecal impaction, or bowel perforation through physical examination and consider abdominal imaging if alarm symptoms present (severe abdominal pain, blood in stool, weight loss) 1, 3
• Assess for other constipation contributors: hypercalcemia, hypokalemia, hypothyroidism, diabetes mellitus, and review all medications for constipating agents 2
• Evaluate defecation patterns: stool frequency, consistency (using Bristol Stool Scale), straining, sensation of incomplete evacuation 1
• Use the Bowel Function Index to objectively measure severity (score ≥30 indicates clinically significant constipation) and monitor treatment response 3, 2, 4

Step 2: Lifestyle Modifications (Concurrent with Pharmacotherapy)

Implement these measures alongside medication, though they are insufficient as monotherapy:

• Increase fluid intake to at least 1.5-2 liters daily if not contraindicated 1, 2
• Encourage regular moderate exercise as tolerated by the patient's condition 1
• Toilet immediately upon urge to defecate and ensure privacy and comfort 1, 3
• Avoid supplemental fiber (psyllium)—it is ineffective for opioid-induced constipation 2

Step 3: First-Line Pharmacological Treatment

Initiate prophylactic laxatives at the same time you start oxycodone—do not wait for constipation to develop:

• Senna 2 tablets (17.2 mg) once daily in the morning OR bisacodyl 5-15 mg once daily 1, 3, 2
• Target goal: one non-forced bowel movement every 1-2 days 3, 2
• Titrate the laxative dose upward when increasing opioid dose 2
• Do NOT use stool softeners (docusate) alone—they are less effective than stimulant laxatives and should not be used as monotherapy 2

Common pitfall: Delaying prophylactic laxatives until constipation develops—up to 80% of patients will experience constipation, and tolerance does not develop 1, 2

Step 4: Second-Line Treatment (If Inadequate Response After 3 Days)

If constipation persists despite adequate stimulant laxative dosing:

• Add an osmotic laxative: Polyethylene glycol (PEG) 17 grams in 8 oz water once to twice daily 3, 2, 5
  • Alternative osmotic agents: lactulose 15-30 mL twice daily or magnesium hydroxide 2, 6
• Increase bisacodyl to 10-15 mg two to three times daily 2, 6
• Re-assess for obstruction or impaction before escalating further 2, 6

Consider rectal interventions if needed:

• Bisacodyl suppository 10 mg or glycerin suppository 2, 6
• Mineral oil retention enema for severe cases 6

Step 5: Third-Line Treatment (Laxative-Refractory OIC)

For patients who fail adequate trials of combination laxatives (stimulant + osmotic for at least 1-2 weeks):

Peripherally Acting μ-Opioid Receptor Antagonists (PAMORAs):

1. Naldemedine 0.2 mg orally once daily (strongest recommendation with high-quality evidence) 3, 2
2. Naloxegol 25 mg orally once daily (strong recommendation with moderate-quality evidence; reduce to 12.5 mg if renal impairment with CrCl <60 mL/min) 1, 3, 2, 7
3. Methylnaltrexone 0.15 mg/kg subcutaneously every other day (conditional recommendation with lower-quality evidence) 1, 3, 2

Critical PAMORA considerations:

• PAMORAs do not cross the blood-brain barrier and will not interfere with oxycodone's analgesic effects 2
• Contraindicated with known or suspected GI obstruction 7
• Naloxegol contraindicated with strong CYP3A4 inhibitors (clarithromycin, ketoconazole); avoid grapefruit juice 7
• Monitor for opioid withdrawal symptoms in patients with disrupted blood-brain barrier 7
• Discontinue if severe abdominal pain or diarrhea develops 7

Step 6: Alternative Strategies for Refractory Cases

If PAMORAs are ineffective or not tolerated:

• Opioid rotation: Switch to equianalgesic dose of transdermal fentanyl or methadone, which may cause less constipation than oral oxycodone 1, 2
• Consider oxycodone/naloxone combination formulation (if switching opioids): This fixed-dose combination has demonstrated improved bowel function without loss of analgesia 1, 8, 9
• Lubiprostone 24 mcg twice daily (intestinal secretagogue, off-label use with limited evidence) 2, 5
• Prokinetic agents: Metoclopramide 10-20 mg four times daily (use cautiously due to risk of tardive dyskinesia, especially in elderly) 2

Step 7: Monitoring and Reassessment

• Use Bowel Function Index at each visit to objectively track response 3, 2, 4
• Reassess for mechanical obstruction if symptoms worsen or become severe 3, 6
• Adjust laxative regimen as opioid dose changes 2
• Discontinue MOVANTIK if oxycodone is discontinued 7
• Resume traditional laxatives if needed after 3 days of PAMORA therapy if symptoms persist 7

Critical Pitfalls to Avoid

• Never delay prophylactic laxatives—start them simultaneously with oxycodone initiation 2
• Never use stool softeners alone without stimulant laxatives—they are ineffective 2
• Never escalate to PAMORAs without ruling out obstruction first 3, 7
• Never use stimulant laxatives during acute diverticulitis with active inflammation (if applicable to patient) 3
• Patients on opioids <4 weeks may be less responsive to PAMORAs 7