Major
Methadone × Moxifloxacin
Synthetic opioid, full mu-receptor agonist×Fourth-generation fluoroquinolone
Mechanism
Methadone prolongs QT (especially above 80 mg/day). Moxifloxacin adds 10-20 ms. Torsades de pointes risk.
Symptoms
QTc above 500 ms, syncope, torsades de pointes risk.
Management
Alternative – levofloxacin or other class.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.