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Drug Interactions between dextromethorphan / quinidine and Mastussin DM

This report displays the potential drug interactions for the following 2 drugs:

  • dextromethorphan/quinidine
  • Mastussin DM (dextromethorphan/guaifenesin)

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Interactions between your drugs


quiNIDine dextromethorphan

Applies to: dextromethorphan / quinidine and Mastussin DM (dextromethorphan / guaifenesin)

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.

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Drug and food interactions


quiNIDine food

Applies to: dextromethorphan / quinidine

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 decrease 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.

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Therapeutic duplication warnings

Therapeutic duplication is the use of more than one medicine from the same drug category or therapeutic class to treat the same condition. This can be intentional in cases where drugs with similar actions are used together for demonstrated therapeutic benefit. It can also be unintentional in cases where a patient has been treated by more than one doctor, or had prescriptions filled at more than one pharmacy, and can have potentially adverse consequences.


NMDA antagonists

Therapeutic duplication

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:

  • dextromethorphan/quinidine
  • Mastussin DM (dextromethorphan/guaifenesin)

Note: The benefits of taking this combination of medicines may outweigh any risks associated with therapeutic duplication. This information does not take the place of talking to your doctor. Always check with your healthcare provider to determine if any adjustments to your medications are needed.

Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.