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Table 1 Severity levels of potential methadone-drug interactions (MDIs) based on Micromedex® and Lexi-Interact™ interaction databases

From: Survey of methadone-drug interactions among patients of methadone maintenance treatment program in Taiwan

Level Definition Drugs
1 a Drugs should not be coadministered as they might lead to serious adverse events or precipitate opioid withdrawal Buprenorphine, Tramadol, Nalbuphine, Naloxone, Naltrexone, Amiodarone, Butorphanol, Ciprofloxacin, Chlorpromazine, Cisapride, Dezocine, Dofetilide, Droperidol, Dronedarone, Fentanyl/Droperidol, Fluphenazine, Fospropofol, Gatifloxacin, Halofantrine, Haloperidol, Ibutilide, Iloperidone, Lapatinib, Levofloxacin, Mesoridazine, Moxifloxacin, Nalbuphine, Nilotinib, Paliperidone, Perphenazine, Pimozide, Prochlorperazine, Promazine, Promethazine, Quinidine, Quinine, Ranolazine, Sotalol, Sunitinb, Tapentadol, Telithromycin, Tetrabenazine, Thiethylperazine, Thioridazine, Trifluoperazine, Vardenafil
2 b A potential interaction might modify the dosage; monitor closely to minimize clinical consequences Alprazolam, Estazolam, Flurazepam, Midazolam, Zopiclone, Clormethiazole, Methylphenidate, Amitriptyline, Desipramine, Imipramine, Nortriptyline, Protriptyline, Phenobarbital, Dexamethasone, Fusidic acid, Rifampicin, Spironolactone, Diltiazem, Cimetidine, Dihydroergotamine, Fluconazole, Ketoconazole, Erythromycin, Clarithromycin, Moclobemide, Fluoxetine, Fluvoxamine, Paroxetine, Sertraline, Risperidone, Merperidine, Alfentanil, Propoxyphene, Morphine, Carbamazepine, Phenytoin
3 c Minor or unknown interactions Dextromethorphan, Nifedipine, Diazepam, Metronidazole, Omeprazole, Verapamil
  1. aThe severity of the MDI was evaluated as a "contraindication" or "major" in Micromedex® and Lexi-Interact™. bA potential MDI may lower or raise serum methadone levels, or drugs that may result in altered metabolism or unpredictable interactions in combination with methadone. cA potential DDI may result in minor or unknown interactions