What is the heart problem that can develop while prescribed Methadone?

Hi ElizaJane, I really don't understand the heart related issues with methadone. I know you've read enough of my answers to know I don't usually "copy & paste" my replies. But I found this info on the topic. I can't really understand it but I think this explains what the issue is. I'm sorry I couldn't give you a better answer. Please discuss this with your doctor. You might want to print this out to have him explain it to you. Hope it helps some!! Best wishes (as always)
chris

Expand this post...

"Cardiac Conduction Effects"
Laboratory studies, both in vivo and in vitro, have demonstrated that Methadone inhibits cardiac potassium channels and prolongs the QT interval. Cases of QT interval prolongation and serious arrhythmia (torsades de pointes) have been observed during treatment with Methadone. These cases appear to be more commonly associated with, but not limited to, higher dose treatment (> 200 mg/day). Most cases involve patients being treated for pain with large, multiple daily doses of Methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In most of the cases seen at typical maintenance doses, concomitant medications and/or clinical conditions such as hypokalemia were noted as contributing factors. However, the evidence strongly suggests that Methadone possesses the potential for adverse cardiac conduction effects in some patients.

Methadone should be administered with particular caution to patients already at risk for development of prolonged QT interval (e.g., cardiac hypertrophy, concomitant diuretic use, hypokalemia, hypomagnesemia). Careful monitoring is recommended when using Methadone in patients with a history of cardiac conduction abnormalities, those taking medications affecting cardiac conduction, and in other cases where history or physical exam suggest an increased risk of dysrhythmia. QT prolongation has also been reported in patients with no prior cardiac history who have received high doses of Methadone. Patients developing QT prolongation while on Methadone treatment should be evaluated for the presence of modifiable risk factors, such as concomitant medications with cardiac effects, drugs which might cause electrolyte abnormalities, and drugs which might act as inhibitors of Methadone metabolism. For use of Methadone to treat pain, the risk of QT prolongation and development of dysrhythmias should be weighed against the benefit of adequate pain management and the availability of alternative therapies.

Methadone treatment for analgesic therapy in patients with acute or chronic pain should only be initiated if the potential analgesic or palliative care benefit of treatment with Methadone has been considered to outweigh the risk of QT prolongation that has been reported with high doses of Methadone.

The use of Methadone in patients already known to have a prolonged QT interval has not been systematically studied.

In using Methadone an individualized benefit to risk assessment should be carried out and should include evaluation of patient presentation and complete medical history. For patients judged to be at risk, careful monitoring of cardiovascular status, including QT prolongation and dysrhythmias and those described previously should be performed.