Quinidine

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Also indexed as:

Quinaglute, Quinidex, Quinora

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

Herbs

Summary of Interactions for Quinidine

Depletion or interference	None known
Adverse interaction	Food Grapefruit juice Low-salt diet Pomegranate juice* Sodium bicarbonate
Side effect reduction/prevention	Beta-carotene Magnesium Potassium
Supportive interaction	Food
Reduced drug absorption/bioavailability	High-salt diet

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 Supplements

Potassium and Magnesium

People taking potassium-depleting diuretics may develop low potassium and magnesium blood levels. Prolonged diarrhea 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.

Other Interactions

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

1. Roden DM, Iansmith DH. Effects of low potassium or magnesium concentrations on isolated cardiac tissue. Am J Med 1987;82:18-23.
2. Fisher DA. Quinidine photosensitivity. Arch Dermatol 1984;120:298 [letter].
3. Damkier P, Hansen LL, Brosen K. Effect of diclofenac, disulfiram, itraconazole, grapefruit juice and erythromycin on the pharmacokinetics of quinidine. Br J Clin Pharmacol 1999;48:829-38.
4. Sorokin AV, Duncan B, Panetta R, Thompson PD. Rhabdomyolysis associated with pomegranate juice consumption. Am J Cardiol 2006;98:705-6.
5. Summers KM. Potential drug-food interactions with pomegranate juice. Ann Pharmacother 2006;40:1472-3.
6. Darbar D, Dell'Orto S, Morike K, et al. Dietary salt increases first-pass elimination of oral quinidine. Clin Pharmacol Ther 1997;61:292-300.
7. Sifton DW, et. Physicians' Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 757-60.
8. Sifton DW, et. Physicians' Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 757-60.

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Last Review: 01-21-2009

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The information presented in Aisle7 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 pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires February 2010.

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