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.¹ Further research is needed to confirm that people taking quinidine can prevent side effects by supplementing with beta-carotene.

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.² 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.

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.³ 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.

Drinking grapefruit juice together with quinidine increases the amount of time that the drug remains in the body,⁴ 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 has been shown to inhibit the same enzyme that is inhibited by grapefruit juice.^{5 , 6} 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.

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.⁷ 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.

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.⁸ 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.