PK-Merz Drug Interactions

The simultaneous use of amantadine and drugs known to cause prolongation of the QT interval is contraindicated.
Examples are: certain antiarrhythmic agents of class I A (e.g. quinidine, disopyramide, procainamide) and class III (e.g. amiodarone, sotalol), certain antipsychotics (e.g. thioridazine, chlorpromazine, haloperidol, pimozide), certain tricyclic and tetracyclic antidepressants (e.g. amitriptyline), certain antihistamines (e.g. astemizole, terfenadine), certain macrolide antibiotics (e.g. erythromycin, clarithromycin), certain gyrase inhibitors (e.g. sparfloxacin), azole antimycotics and other drugs such as budipine, halofantrine, co-trimoxazole, pentamidine, cisapride and bepridil.
This list cannot be exhaustive. Before commencing use of amantadine concomitantly with another drug, the SPC of the latter should be checked for potential interactions, due to QT prolongation, between the drug and amantadine.
Use of Amantadine Sulphate (PK-Merz) 100 mg film-coated tablets in combination with other antiparkinsonian drugs is possible. To avoid undesirable effects (such as psychotic reactions), it may be necessary to reduce the dosage of the other drugs or of the combination.
There have been no specific studies on the occurrence of interactions after administration of Amantadine Sulphate (PK-Merz) 100 mg film-coated tablets concomitantly with other antiparkinsonian drugs (e.g. levodopa, bromocriptine, trihexyphenidyl, etc.) or memantine (see Adverse Reactions).
Simultaneous treatment with Amantadine Sulphate (PK-Merz) 100 mg film-coated tablets and any of the drug types or active substances listed as follows may lead to the following interactions: Anticholinergics: Enhancement of the undesirable effects (confusion and hallucinations) of anticholinergics (e.g. trihexyphenidyl, benzatropine, scopolamine, biperiden, orphenadrine, etc.).
Indirectly CNS-active sympathomimetics: Potentiation of the central effects of amantadine.
Alcohol: Lowering of alcohol tolerance.
Levodopa (antiparkinsonian drug): Mutual potentiation of the therapeutic action. Levodopa can therefore be given concomitantly with Amantadine Sulphate (PK-Merz) 100 mg film-coated tablets.
Memantine (anti-dementia drug): Memantine can potentiate the effect and undesirable effects of Amantadine Sulphate (PK-Merz) 100 mg film-coated tablets (see Precautions).
Other drugs: The simultaneous use of diuretics of the triamterene/hydrochlorothiazide combination type can result in a decrease in the plasma clearance of amantadine, leading to toxic plasma concentrations. Simultaneous use should therefore be avoided.