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Methylnaltrexone Versus Naloxone for Opioid-Induced Constipation in the Medical Intensive Care Unit
Methylnaltrexone Versus Naloxone for Opioid-Induced Constipation in the Medical Intensive Care Unit
Merchan C, Altshuler D, Papadopoulos J. Ann Pharmacother. 2017; 51(3): 203-8.
Study Question: Is the use of subcutaneous methylnaltrexone (MNTX) as safe and effective as enteral naloxone (NTX) for treatment of opioid induced constipation in the medical ICU?
Study Description: This single-center, retrospective cohort was performed in patients who received either subcutaneous MNTX or enteral NTX for treatment of opioid-induced constipation (OIC) defined as absence of a bowel movement (BM) for ≥ 72 hours while receiving continuous infusion fentanyl. Exclusion criteria were active colitis, mechanical bowel obstruction, surgical abdomen, or inability to receive enteral NTX. The primary endpoint was time to first BM. Secondary endpoints included doses of NTX or MNTX prior to BM, number of BMs in 48 hours, opioid usage after study drug, and change in heart rate, MAP, and RASS after study drug. A cost analysis and a post hoc analysis of patients on vasopressors were also conducted. NTX was most commonly prescribed at 1-2mg orally q6h and MNTX at 8 mg for patients 38 to 61 kg and 12mg for patients 61 to 114 kg.
Results: Of the 100 patients included, 52 received NTX and 48 received MNTX. The median time to first BM was 30 hours and 24 hours respectively (p = 0.165). There were no significant differences in secondary endpoints or in the post hoc analysis of the 78 patients on vasopressors. No increase in opioid requirement was observed in either group. MNTX was significantly more cost-effective than NTX in producing one BM ($120 vs $197.90, p = 0.01).
Conclusion(s): Both NTX and MNTX appear to be safe and effective for the treatment of OIC.
Perspective: Mu opioid-receptor antagonists show promise for the treatment OIC for the medically critically ill patient on continuous opioid infusions for analgosedation. This study demonstrated that administration of NTX and MNTX did not increase opioid requirements and the efficacy of subcutaneous MNTX was not effected by vasopressors. Methylnaltrexone may be equally safe and effective as oral naloxone for OIC while being more cost effective. Importantly, 30% of patients were not on a bowel regimen and the majority of others were only on docusate-senna. Optimizing bowel regimen prior to MNTX or NTX administration may provide further cost savings.