Drug Interaction Report

Using dextromethorphan together with quiNIDine may increase the effects of dextromethorphan. Contact your doctor if you experience difficulty breathing, dizziness, drowsiness, anxiety, restless feeling, nervousness, confusion, or diarrhea. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Using amantadine together with quiNIDine may increase the effects of amantadine. Contact your doctor if you experience blurred vision, severe headache, nausea, vomiting, anxiety, confusion, aggression, tremor, fast or uneven heart rate, trouble breathing, or seizure (convulsion). If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Do not consume grapefruit or grapefruit juice during treatment with quiNIDine unless specifically directed otherwise by your doctor. Grapefruit and grapefruit juice can interact with quiNIDine and increase the levels of quiNIDine in your body. If you are already consuming grapefruit products, do not increase or decrease the amount of these products in your diet without first talking to your doctor.

Alcohol can increase the nervous system side effects of dextromethorphan such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with dextromethorphan. Do not use more than the recommended dose of dextromethorphan, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.

The recommended maximum number of medicines in the 'NMDA antagonists' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'NMDA antagonists' category:

• amantadine
• dextromethorphan / quinidine

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.