See also the How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include: fingolimod, propafenone.

Other medications can affect the removal of quinidine from your body, which may affect how quinidine works. Examples include cobicistat, mifepristone, ritonavir, certain azole antifungals (including fluconazole, itraconazole, ketoconazole, posaconazole, voriconazole), certain protease inhibitors (such as nelfinavir, tipranavir), among others.

This medication can slow down the removal of other medications from your body, which may affect how they work. Examples of affected drugs include aliskiren, codeine, digoxin, mefloquine, tricyclic antidepressants (such as desipramine, imipramine), among others.

Many drugs besides quinidine may affect the heart rhythm (QT prolongation), including artemether/lumefantrine, ranolazine, toremifene, antiarrhythmic drugs (such as amiodarone, disopyramide, dofetilide, dronedarone, ibutilide, procainamide, sotalol), antipsychotics (such as pimozide, thioridazine, ziprasidone), certain quinolone antibiotics (grepafloxacin, sparfloxacin), among others.

Quinidine is very similar to quinine. Do not use medications containing quinine while using quinidine.