Verapamil with Quinidine Interaction Details

Brand Names Associated with Verapamil

Brand Names Associated with Quinidine

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated Dec 03, 2023

Interaction Effect

Hypotension, counteraction by verapamil of quinidine's effect on AV conduction, and possible quinidine toxicity (ventricular arrhythmias, hypotension, exacerbation of heart failure)

Interaction Summary

Verapamil significantly reduces hepatic clearance of quinidine, with a corresponding increase in serum levels and half-life of quinidine. Several reports suggest that the concurrent use of quinidine and verapamil results in hypotension and possibly pulmonary edema . Felodipine does not appear to alter quinidine kinetics . Also, verapamil has been shown to significantly counteract the effects of quinidine on AV conduction and may increase quinidine levels during concurrent therapy .

Severity

Moderate

Onset

Rapid

Evidence

Probable

How To Manage Interaction

Monitor blood pressure closely for hypotension, and also monitor for quinidine toxicity, including laboratory confirmation of alterations in serum quinidine levels. Avoid use of this combination in patients with hypertrophic cardiomyopathy.

Mechanism Of Interaction

Additive effects; inhibition of quinidine metabolism

Literature Reports

A) Serious complications were noted in three patients with hypertrophic cardiomyopathy who were receiving concomitant oral verapamil and quinidine. In two patients receiving verapamil 120 mg four times daily, severe hypotension occurred after three doses of quinidine 320 mg and 600 mg. In one of these patients, pulmonary edema developed and the other had short bursts of ventricular tachycardia and unobtainable blood pressure. The third patient received quinidine first and developed pulmonary edema and hypotension when verapamil 120 mg four times daily for 13 doses was added .

B) Concomitant administration of verapamil and quinidine was reported to result in a reduction in clearance and prolongation of the half-life of quinidine . The formation clearance of 3-hydroxyquinidine was reduced significantly after pretreatment with verapamil; the renal clearance of unchanged quinidine was unaffected. This study involved six healthy male volunteers; more studies are required in patients with cardiovascular disease to determine the clinical significance of this interaction.

Verapamil Overview

• Verapamil is used to treat high blood pressure and to control angina (chest pain). The immediate-release tablets are also used alone or with other medications to prevent and treat irregular heartbeats. Verapamil is in a class of medications called calcium-channel blockers. It works by relaxing the blood vessels so the heart does not have to pump as hard. It also increases the supply of blood and oxygen to the heart and slows electrical activity in the heart to control the heart rate.

• High blood pressure is a common condition and when not treated, can cause damage to the brain, heart, blood vessels, kidneys and other parts of the body. Damage to these organs may cause heart disease, a heart attack, heart failure, stroke, kidney failure, loss of vision, and other problems. In addition to taking medication, making lifestyle changes will also help to control your blood pressure. These changes include eating a diet that is low in fat and salt, maintaining a healthy weight, exercising at least 30 minutes most days, not smoking, and using alcohol in moderation.

Quinidine Overview

• Quinidine is used to treat certain types of irregular heartbeats. Quinidine is in a class of medications called antiarrhythmic medications. It works by making your heart more resistant to abnormal activity.

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Definitions

Severity Categories

Contraindicated

These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.

Major

This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.

Moderate

This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.

Minor

While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.

Onset

Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.

Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.

Evidence

Level of documentation of the interaction.

Established: The interaction is documented and substantiated in peer-reviewed medical literature.

Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.

How To Manage The Interaction

Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.

It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.

Mechanism Of Interaction

The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.

Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.

Where Does Our Information Come From?

Information for our drug interactions is compiled from several drug compendia, including:

• Gold Standard Drug Database
• Micromedex
• Lexicomp
• DrugBank

The prescribing information for each drug, as published on DailyMED, is also used. 

Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.

The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.