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35th AM (2025) - Poster Session
Methadone in the Setting of QTc Prolongation and I ...
Methadone in the Setting of QTc Prolongation and Implantable Cardioverter-Defibrillator
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This discussion addresses cardiac monitoring recommendations for patients receiving methadone treatment, particularly focusing on QTc interval prolongation risks. The American Society of Addiction Medicine and American Pain Society guidelines advise conducting a baseline EKG for patients with risk factors prior to methadone initiation, followed by an EKG within 30 days and annually thereafter. More frequent EKG assessments are recommended when methadone doses exceed 100 mg daily.<br /><br />Methadone, a long-acting full opioid agonist effective for opioid use disorder (OUD) treatment, can block cardiac hERG potassium channels, delaying ventricular repolarization and causing dose-dependent QTc prolongation. Approximately 2-10% of patients on methadone develop significant QTc prolongation (≥500 ms), which greatly increases the risk of Torsades de Pointes (TdP), potentially progressing to ventricular fibrillation. This risk is heightened in the presence of electrolyte imbalances (e.g., hypokalemia, hypomagnesemia), liver disease, drug interactions (notably CYP3A4 inhibitors), or structural heart disease.<br /><br />For patients with QTc intervals between 450-500 ms, clinicians should assess reversible causes and carefully weigh the risks versus benefits of continuing methadone, implementing more frequent cardiac monitoring if necessary. When QTc exceeds 500 ms, switching to alternative treatments is strongly advised, including buprenorphine for medication for opioid use disorder (MOUD) or full opioid agonists in chronic pain management.<br /><br />Notably, buprenorphine is not linked to clinically significant QTc prolongation at therapeutic doses, even in patients transitioning from methadone due to QTc concerns. During cross-tapering from methadone to buprenorphine, a microdose induction protocol with cardiac monitoring is recommended in stable patients. This approach aims to minimize cardiac risks while maintaining effective opioid use disorder management. The recommendations are adapted from clinical case reports and published guidelines to inform safe opioid pharmacotherapy practices.
Keywords
methadone
QTc prolongation
cardiac monitoring
EKG
opioid use disorder
Torsades de Pointes
buprenorphine
hERG potassium channels
electrolyte imbalances
CYP3A4 inhibitors
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