Quinidine | Health Notes at WWSM | Health Information at WWSM

Quinidine

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Also indexed as: Kinidin Durules, Quinaglute, Quinidex, Quinora

Quinidine is used to treat and prevent certain forms of heart arrhythmia.

Summary of Interactions with Vitamins, Herbs, and Foods
In some cases, a herb or supplement may appear in more than one category, which may seem contradictory. For clarification, read the full article for details about the summarized interactions.

May Be Beneficial: Side effect reduction/prevention—Taking these supplements may help reduce the likelihood and/or severity of a potential side effect caused by the medication.	Beta-carotene Magnesium Potassium
May Be Beneficial: Supportive interaction—Taking these supplements may support or otherwise help your medication work better.	Food
Avoid: Reduced drug absorption/bioavailability—Avoid these supplements when taking this medication since the supplement may decrease the absorption and/or activity of the medication in the body.	High-salt diet
Avoid: Adverse interaction—Avoid these supplements when taking this medication because taking them together may cause undesirable or dangerous results.	Food Grapefruit juice Low-salt diet Pomegranate juice* Sodium bicarbonate
Depletion or interference	None known

An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

Interactions with Dietary Supplements

Potassium and Magnesium
People taking potassium-depleting diuretics may develop low potassium and magnesium blood levels. Prolonged diarrhoea and vomiting might also result in low blood potassium levels. People with low potassium or magnesium blood levels who take quinidine might develop serious drug side effects.¹ Therefore, people taking quinidine should have their blood potassium and magnesium levels checked regularly and might need to supplement with both minerals, especially when taking potassium-depleting diuretics.

Beta-carotene
Some people taking quinidine develop sensitivity to ultraviolet radiation from the sun. In a preliminary study, three people with quinidine-induced skin inflammation were able to tolerate intense sun exposure without recurrence of the rash after supplementing with 90–180 mg of beta-carotene each day.² Further research is needed to confirm that people taking quinidine can prevent side effects by supplementing with beta-carotene.

Interaction with Foods and Other Compounds

Grapefruit juice
Drinking grapefruit juice together with quinidine increases the amount of time that the drug remains in the body,³ which might increase the likelihood of side effects and toxicity. Therefore, based on currently available information, people taking quinidine should avoid drinking grapefruit juice or eating grapefruit.

Pomegranate juice
Pomegranate juice has been shown to inhibit the same enzyme that is inhibited by grapefruit juice.⁴ ⁵ The degree of inhibition is about the same for each of these juices. Therefore, it would be reasonable to expect that pomegranate juice might interact with quinidine in the same way that grapefruit juice does.

Salt
One controlled study showed that people consuming a high-salt diet had dramatically lower quinidine blood levels compared with people on a low-salt diet.⁶ Problems might occur when people switch from a high-salt diet to a low-salt diet and vice versa. Therefore, people taking quinidine should notify their health practitioner before changing their salt intake.

Food
Taking quinidine with food greatly increases the speed and extent of absorption of the drug.⁷ Serious problems might occur when people switch from taking quinidine with a meal to taking it on an empty stomach and vice versa. Therefore, quinidine should be consistently taken with a meal to enhance drug action and to avoid potential problems.

Sodium bicarbonate
Sodium bicarbonate reduces the amount of quinidine eliminated from the body, which might result in increased drug side effects and toxicity.⁸ Therefore, people taking quinidine should avoid using antacids or toothpaste that contain sodium bicarbonate.

References
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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires September 2008.

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Interactions with Dietary Supplements

Interaction with Foods and Other Compounds