391 First Reported Use of Methylnaltrexone to Treat Opioid-Induced Constipation in a Pediatric Burn Patient

Abstract

Pain in critically ill pediatric burn patients is a complex and challenging issue whose adequate control is further complicated by anticipative fear and anxiety. Undertreated pain increases risk for post-burn PTSD and other psychosocial impairments, so it is aggressively managed with regimens often including high-dose opiates. This often results in Opioid-Induced Constipation (OIC) and first line laxative treatments have high recurrence rates due to the continuous, direct gastrointestinal effects of μ-opioid antagonism. Methylnaltrexone (MLTX), an FDA-approved injectable µ-opioid receptor antagonist, selectively acts on the myenteric plexus to reverse OIC without crossing the blood-brain-barrier to impair systemic analgesia. MLTX is safe and highly efficacious at treating OIC in adult and pediatric oncologic patients with recent data showing great effect in adult burn patients. Here we report the first case of the safe and efficacious reversal of OIC in a critically ill pediatric burn patient who failed standard laxative therapies. A retrospective case review was performed on a pediatric burn patient who was treated with MLTX for OIC in the setting of high-dose intravenous opiates. In our unit, MLTX is reserved for patients who remain without a bowel movement for 3 or more consecutive days on escalating regimens of traditional laxatives, particularly if they have worsening abdominal pain, distension, bladder pressures, or intolerance to enteral feeding. Following approval by a pediatric gastroenterologist and pharmacist, subcutaneous MLTX was administered at a dose of 0.15 mg/kg. Any complications related to drug administration (e.g. new abdominal pain, nausea, or bowel perforation) were tracked for risk analysis. Patient was an 11-year-old female with 18% TBSA partial and full thickness burns to face, trunk, and all four extremities with inhalation injury from a house fire. She was intubated prior to arrival, averaged 114 mg morphine equivalents per day, and stopped responding to first line laxation therapy after 12 days, subsequently going 4 days without laxation. She was given 8 mg MLTX with laxation 19 hours after administration. There were no adverse events associated with MLTX administration. MLTX administered as a single dose of 0.15 mg/kg subcutaneously was safely used to induce laxation in a critically ill pediatric burn patient with no observed adverse effects. To our knowledge, this is the first reported case of treating OIC with MLTX in a pediatric burn patient. Larger studies are indicated to further elucidate the safety and efficacy profile of MLTX in pediatric burn patients. MLTX may be a safe and efficacious treatment for OIC in pediatric burn patients requiring high-dose opiates.