Quinidine
Quinidine is a Class IA antiarrhythmic medication that works by blocking sodium channels in the heart, prolonging the action potential duration, and increasing the refractory period of cardiac tissue. It is used to treat various cardiac arrhythmias and also serves as a cytochrome P450 2D6 inhibitor, which increases plasma levels of drugs like dextromethorphan when used in combination products. The medication is derived from cinchona bark and has been used clinically for decades in managing rhythm disorders.
Quinidine is an antiarrhythmic medication that treats heart rhythm disorders by blocking sodium channels and can also inhibit CYP2D6 enzyme activity.
Key facts at a glance
- ATC
- C01BA01
- RxNorm
- 9068
- Generic
- Quinidine
- Class
- atc-c01
- Brands
- Nuedexta
- Availability
- rx
- Lactation
- unknown
- Routes
- oral
- Forms
- capsule, tablet
- Regions
- US, EU, CN, JP
- Monitoring
- —
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Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Treatment of cardiac arrhythmias including atrial fibrillation, atrial flutter, supraventricular tachycardia, and ventricular arrhythmias. Also used in combination with dextromethorphan for pseudobulbar affect and previously for malaria treatment.
Quinidine is a Class IA antiarrhythmic that blocks sodium channels, prolongs the action potential duration, and increases the effective refractory period of cardiac tissue. Additionally, it competitively inhibits cytochrome P450 2D6 enzyme, which increases plasma concentrations of drugs metabolized by this pathway.
Requires careful cardiac monitoring due to proarrhythmic risk. Contraindicated in patients with AV block, Bundle Branch Block, or severe heart failure. Can cause cinchonism (tinnitus, headache, blurred vision). Multiple drug interactions due to CYP450 inhibition. Requires therapeutic drug monitoring to maintain appropriate levels.
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 26, 2026. · Read our editorial policy