Your healthcare professionals (e.g., doctor or pharmacist) may already be aware of any possible drug interactions and may be monitoring you for it. Do not start, stop or change the dosage of any medicine before checking with them first.
This drug should not be used with the following medications because very serious interactions may occur: naltrexone, drugs which may affect the heart rhythm (QT prolonging drugs such as bepridil, droperidol, halofantrine, mesoridazine, pimozide, sertindole, sparfloxacin).
If you are currently using any of these medications, tell your doctor or pharmacist before starting methadone.
Other drugs besides methadone which may affect the heart rhythm (QT prolongation in the EKG) include amiodarone, dofetilide, erythromycin, moxifloxacin, procainamide, quinidine, and sotalol, among others. Before using methadone, report all medications you are currently using to your doctor or pharmacist. QT prolongation can infrequently result in serious (rarely fatal) fast/irregular heartbeat and other symptoms (e.g., severe dizziness, fainting) that require immediate medical attention. Ask your doctor or pharmacist for more details and for instructions on how you may reduce the risk of this effect.
Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: amphetamines, blood thinners (e.g., warfarin), drugs affecting liver enzymes that remove methadone from your body (such as azole antifungals-including itraconazole, cimetidine, efavirenz, fluvoxamine, macrolide antibiotics-including erythromycin, nevirapine, protease inhibitors-including ritonavir, rifamycins-including rifampin, St. Johns wort, certain anti-seizure medicines including phenytoin), MAO inhibitors (e.g., furazolidone, isocarboxazid, linezolid, moclobemide, phenelzine, procarbazine, rasagiline, selegiline, tranylcypromine), certain nucleoside analogues (e.g., didanosine, stavudine, zidovudine), pentazocine, certain "water pills" (potassium-wasting diuretics such as hydrochlorothiazide, furosemide).
Tell your doctor or pharmacist if you also take drugs that cause drowsiness such as: anesthesia drugs, certain antihistamines (e.g., diphenhydramine), anti-anxiety drugs (e.g., diazepam), anti-seizure drugs (e.g., carbamazepine), medicine for sleep (e.g., sedatives), muscle relaxants, other narcotic pain relievers (e.g., codeine), psychiatric medicines (e.g., phenothiazines such as chlorpromazine, or tricyclics such as amitriptyline and desipramine), tranquilizers.
Check the labels on all your medicines (e.g., cough-and-cold products) because they may contain drowsiness-causing ingredients. Ask your pharmacist about the safe use of those products.
This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.