Impact of Enteral Methadone on the Ability to Wean Off Continuously Infused Opioids in Critically Ill, Mechanically Ventilated Adults: A Case-Control Study

BACKGROUND: Continuously infused opioids are frequently used to optimize patient comfort in the intensive care unit (ICU). However, concerns about rebound pain and opioid withdrawal may delay efforts to discontinue this therapy. OBJECTIVE: To measure the association between use of scheduled enteral methadone according to a protocol in mechanically ventilated, medical critically ill adults receiving prolonged continuously infused fentanyl and the time to discontinue continuously infused fentanyl therapy. METHODS: This case-control study included 20 consecutive mechanically ventilated adults in a medical ICU, without a history of chronic opioid use, who received 72 or more hours of continuously infused fentanyl and were prescribed scheduled enteral methadone as part of a protocol medical ICU strategy to wean off continuously infused fentanyl. Patients were matched in a 1:2 fashion, by duration of mechanical ventilation, to 40 consecutive preprotocol medical ICU patients meeting the same criteria but who were never given methadone. Duration of continuously infused fentanyl was compared between the 2 groups by constructing Kaplan-Meier plots and estimating the likelihood that methadone use was associated with a decrease in continuously infused fentanyl requirements over time, using a Cox proportional hazards model. RESULTS: The groups were well matched except the methadone patients were older (p = 0.04). Time (median [interquartile range]) to continuously infused fentanyl discontinuation was shorter in the methadone group (4.5 [3.9-5.8] vs 7.0 [4.9-11.5] days; p = 0.002). Continuously infused fentanyl was more likely to be discontinued 2 days after methadone was first initiated (hazard ratio 9.1; p = 0.0004). The proportion of patients who experienced 1 or more episodes of either QTc interval prolongation (p = 0.79) or unarousability (p = 0.47) was similar between the groups. CONCLUSIONs: Enterally administered methadone is associated with earlier cessation of continuously infused fentanyl in mechanically ventilated adults without a history of opioid dependence admitted to a medical ICU. Prospective, controlled studies are needed to further evaluate the safety and efficacy of methadone as a strategy to wean off continuously infused fentanyl in different ICU populations.