A 28-year-old male on methadone maintenance therapy (80 mg/day) for opioid use disorder presents with acute onset of severe abdominal pain, vomiting, and constipation for 3 days. Physical examination reveals abdominal distension and absent bowel sounds. He denies recent increase in methadone dose or concurrent opioid use. What is the most appropriate immediate next step?

Question

Accepted Answer

B. Obtain abdominal imaging (X-ray or CT) and manage as acute abdomen; consider temporary methadone dose reduction if ileus confirmed. ## Acute Abdomen in a Patient on Methadone: Diagnostic Priority

**Key Point:** Acute abdominal pain with vomiting and absent bowel sounds in a methadone-maintained patient is a surgical emergency until proven otherwise. While methadone-induced constipation is common, acute abdomen requires imaging to exclude mechanical obstruction, perforation, or other surgical pathology.

### Clinical Reasoning

**High-Yield:** Opioids (including methadone) cause constipation via μ-receptor activation in the GI tract, but acute severe symptoms with ileus suggest either:
1. **Mechanical obstruction** (adhesions, impaction, volvulus)
2. **Paralytic ileus** (severe opioid-induced or post-surgical)
3. **Acute surgical abdomen** (perforation, appendicitis, pancreatitis)

### Management Algorithm for Acute Abdomen in Methadone Patient

```mermaid
flowchart TD
  A[Acute abdominal pain + vomiting + absent bowel sounds]:::outcome --> B[Obtain abdominal imaging: X-ray ± CT]:::action
  B --> C{Mechanical obstruction or perforation?}:::decision
  C -->|Yes| D[Surgical consultation & intervention]:::urgent
  C -->|No| E{Paralytic ileus?}:::decision
  E -->|Yes, severe| F[Reduce methadone dose by 25-50%]:::action
  E -->|Mild| G[Conservative: NPO, IV fluids, laxatives]:::action
  F --> H[Monitor bowel function & methadone levels]:::action
  G --> H
  H --> I[Restart methadone when ileus resolves]:::action
```

**Warning:** Do NOT assume all abdominal pain in methadone patients is drug-induced constipation. This is a common cognitive error that delays diagnosis of surgical emergencies.

### Methadone-Induced Constipation: Pathophysiology & Management

| Feature | Mechanism | Management |
|---------|-----------|------------|
| **Frequency** | 40–90% of methadone patients | Preventive: high-fibre diet, hydration |
| **Cause** | μ-receptor agonism → ↓ GI motility, ↑ fluid reabsorption | Osmotic laxatives (polyethylene glycol, lactulose) |
| **Severity** | Usually mild-to-moderate; rarely causes acute ileus | Stimulant laxatives (senna, bisacodyl) if needed |
| **Prevention** | Prophylactic laxatives recommended | Naloxone-containing formulations (not available in India) |

**Clinical Pearl:** Methadone-induced constipation is chronic and predictable; acute severe symptoms with ileus are NOT typical and warrant urgent investigation.

### Why Each Step Matters

1. **Imaging first**: Rules out surgical emergency (obstruction, perforation).
2. **Dose reduction if ileus confirmed**: Reduces opioid load and allows GI recovery.
3. **Psychosocial support continues**: Do NOT abandon counselling during acute illness.
4. **Restart methadone when safe**: Prevents withdrawal and relapse.

**Tip:** If ileus is confirmed as opioid-induced (imaging negative, clinical improvement with dose reduction), reduce methadone by 25–50% and monitor carefully. Once bowel function normalizes, titrate back to therapeutic dose.

Answer

A. Increase methadone dose to 120 mg/day to suppress withdrawal symptoms and improve GI motility

Answer

C. Discontinue methadone immediately and switch to buprenorphine to reduce opioid-induced constipation

Answer

D. Prescribe laxatives and antiemetics; reassure the patient that methadone-induced constipation is self-limiting

Explanation

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