.
Quinidine is used to treat and prevent certain forms of heart arrhythmia.
Interactions with Dietary 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.
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.
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.4 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.5 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.6 Therefore, people taking
quinidine should avoid using antacids or toothpaste that contain sodium bicarbonate.
Summary of Interactions for Quinidine
| Depletion or interference | None known |
|---|---|
| Adverse interaction | Food Grapefruit juice Low-salt diet Sodium bicarbonate |
| Side effect reduction/prevention |
Beta-carotene Magnesium Potassium |
| Supportive interaction | Food |
| Reduced drug absorption/bioavailability | High-salt diet |
For the convenience of the reader, the information in the summary is categorized as follows: “Depletion or interference” indicates the drug may deplete or interfere with the absorption or function of the supplement or herb. “Adverse interaction” indicates that the supplement or herb used together with the drug may result in undesirable effects. “Side effect reduction/prevention” indicates the supplement or herb may reduce the likelihood and/or severity of a potential side effect caused by the drug. “Supportive interaction” indicates the supplement or herb may support or aid the function of the drug. “Reduced drug absorption/bioavailability” indicates that the supplement or herb may decrease the absorption and/or activity of the drug in the body. An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.
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. 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.
5. Sifton DW, et. Physicians’ Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 757–60.
6. Sifton DW, et. Physicians’ Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 757–60.
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The information presented in VitaminLore 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.