Digoxin

Safetychecker Summary for Digoxin
(for details about the summarized interactions, read the full article)

May be Beneficial: Depletion or interference—The medication may deplete or interfere with the absorption or function of the nutrient. Taking these nutrients may help replenish them.	Magnesium Potassium (if levels are low)
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.	Magnesium Potassium
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.	Senna* St. John’s wort*
Avoid: Adverse interaction—Avoid these supplements when taking this medication because taking them together may cause undesirable or dangerous results.	Cascara* Eleuthero* Licorice* Sarsaparilla Senna* Digitalis Pleurisy root
Check: Other—Before taking any of these supplements or eating any of these foods with your medication, read this article in full for details.	Alder buckthorn* Buckthorn* Hawthorn Potassium*
Supportive interaction	None known

Interactions with Dietary Supplements

Magnesium
People needing digoxin may have low levels of potassium or magnesium,¹ increasing the risk for digoxin toxicity. Digoxin therapy may increase magnesium elimination from the body.² People taking digoxin may benefit from magnesium supplementation.³ Medical doctors do not commonly check magnesium status, and when they do, they typically use an insensitive indicator of magnesium status (serum or plasma levels). The red blood cell magnesium level may be a more sensitive indicator of magnesium status, although evidence is conflicting. It has been suggested that 300–500 mg of magnesium per day is a reasonable amount to supplement.⁴

Potassium
Medical doctors prescribing digoxin also check for potassium depletion and prescribe potassium supplements if needed. Potassium transport from the blood into cells is impaired by digoxin.⁵ Although digoxin therapy does not usually lead to excess potassium in the blood (hyperkalemia), an overdose of digoxin could cause a potentially fatal hyperkalemia.⁶ People taking digoxin should therefore avoid taking potassium supplements, or eating large quantities of fruit (e.g., bananas), unless directed to do so by their doctor. On the other hand, many people taking digoxin are also taking a diuretic; in these individuals, increased intake of potassium may be needed. These issues should be discussed with a doctor.

Interactions with Herbs

Alder Buckthorn, Buckthorn (Rhamnus catartica, Rhamnus frangula, Frangula alnus)
Use of buckthorn or alder buckthorn for more than ten days consecutively may cause a loss of electrolytes (especially the mineral potassium). Loss of potassium may increase the toxicity of digitalis-like medications with potentially fatal consequences.⁷

Cascara (Rhamnus purshiani cortex)
Loss of potassium due to cascara abuse could theoretically increase the effects of digoxin and other similar heart medications, with potentially fatal consequences. However, no cases of such an interaction have yet been reported.

Digitalis (Digitalis purpurea)
Digitalis refers to a group of plants commonly called foxglove that contain chemicals with actions and toxicities similar to digoxin. Digitalis was used as an herbal medicine to treat some heart conditions before the drug digoxin was available. Some doctors continue to use digitalis in the United States, and it is used as an herbal medicine in other countries as well. Due to the additive risk of toxicity, digitalis and digoxin should never be used together.

Eleuthero (Eleutherococcus senticosus)
People taking digoxin require regular monitoring of serum digoxin levels. In one report, addition of a product identified as Siberian ginseng to stable, therapeutic digoxin treatment was associated with dangerously high serum digoxin levels.⁸ The patient never experienced symptoms of digoxin toxicity. Laboratory analysis found the product was free of digoxin-like compounds but the contents were not further identified. This report may reflect an interaction of eleuthero with the laboratory test to cause a falsely elevated reading, rather than actually increasing digoxin levels.

Hawthorn (Crataegus oxyacantha, Crataegus monogyna)
Hawthorn (leaf with flower) extract is approved in Germany to treat mild congestive heart failure.⁹ Congestive heart failure is a serious medical condition that requires expert medical management rather than self-treatment. Due to the narrow safety index of digoxin, it makes sense for people taking digoxin for congestive heart failure to consult with their doctor before using hawthorn-containing products. Reports of hawthorn interacting with digitalis to enhance its effects have not been confirmed.

Licorice (Glycyrrhiza glabra)
Potassium deficiency increases the risk of digoxin toxicity. Excessive use of licorice plant or licorice plant products may cause the body to lose potassium.¹⁰ Artificial licorice flavoring does not cause potassium loss. People taking digoxin should read product labels carefully for licorice plant ingredients.

Pleurisy root
As pleurisy root and other plants in the Aesclepius genus contain cardiac glycosides, it is best to avoid use of pleurisy root with heart medications such as digoxin.¹¹

Sarsaparilla (Smilax spp.)
Sarsaparilla may increase the absorption of digitalis and bismuth, increasing the chance of toxicity.¹²

Senna (Cassia senna, Cassia angustifolia)
Bisacodyl, a laxative similar in action to senna, given with digoxin decreased serum digoxin levels in healthy volunteers compared with digoxin alone.¹³ In patients taking digoxin, laxative use was also associated with decreased digoxin levels.¹⁴ In addition, concern has been expressed that overuse or misuse of senna may deplete potassium levels and increase both digoxin activity and risk of toxicity.¹⁵ However, overuse of senna could also decrease digoxin activity because, as noted, laxatives can decrease the levels of the drug.

St. John’s wort (Hypericum perforatum)
One preliminary trial has suggested that St. John’s wort may reduce blood levels of digoxin.¹⁶ In this study, healthy volunteers took digoxin for five days, after which they added 900 mg per day of St. John’s wort while continuing the daily digoxin. A normal blood level of digoxin was reached after five days of taking the drug, but this level dropped significantly when St. John’s wort was added. This may have occurred because certain chemicals found in St. John’s wort activate liver enzymes that are involved in the elimination of some drugs.¹⁷ ¹⁸ Until more is known, people taking digoxin should avoid St. John’s wort.

References:

1. Whang R, Oei TO, Watanabe A. Frequency of hypomagnesiumia in hospitalized patients receiving digitalis. Arch Intern Med 1985;145:655–6.

2. Holt GA. Food & Drug Interactions. Chicago: Precept Press, 1998, 94.

3. Landauer RA. Magnesium deficiency and digitalis toxicity. JAMA 1984;251:730 [letter/review].

4. Cohen L, Kitzes R. Letter. JAMA 1984;251:730.

5. Lown B, Black H, Moore FD. Digitalis, electrolytes and the surgical patient. Am J Cardiol 1960;6:309–37.

6. Smith TW, Willerson JT. Suicidal and accidental digoxin ingestion. Report of five cases with serum digoxin level correlations. Circulation 1971;44:29–36.

7. European Scientific Cooperative on Phytotherapy (ESCOP). Frangulae cortex, frangula bark. Monographs on the Medicinal Uses of Plant Drugs. Exeter, UK: University of Exeter, Centre for Complementary Health Studies, 1997.

8. McRae S. Elevated serum digoxin levels in a patient taking digoxin and Siberian ginseng. Can Med Assoc J 1996;155:293–5.

9. Blumenthal M, ed. The Complete German Commission E Monographs. Austin, TX: American Botanical Council, 1998, 143.

10. Tyler VE. The Honest Herbal, 3rd ed. New York: Pharmaceutical Products Press, 1993, 198.

11. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press, 1996, 213–4.

12. Bradley PR (ed). British Herbal Compendium, vol 1. Bournemouth, Dorset, UK: British Herbal Medicine Association, 1992, 194–6.

13. Wang DJ, Chu KM, Chen JD, et al. Drug interaction between digoxin and bisacodyl. J Formos Med Assoc 1990;89:913, 915–9 [in Chinese].

14. Botzler R, Ritter U. Effect of laxative measures on the serum concentration of digoxin in the human. Leber Magen Darm Nov 1982; 14(6):255–7 [in German].

15. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide for Healthcare Professionals. London: Pharmaceutical Press, 1996, 244.

16. Johne A, Brockmöller, Bauer S, et al. Pharmacokinetic interaction of digoxin with an herbal extract from St. John’s wort (Hypericum perforatum). Clin Pharmacol Ther 1999;66:338–45.

17. Nebel A, Schneider BJ, Baker RK, Kroll DJ. Potential metabolic interaction between St. John’s wortand theophylline [letter]. Ann Pharmacother 1999;33:502.

18. Mai I, Schmider J, et al. Unpublished results, May, 1999. Reported in: Johne A, Brockmöller, Bauer S, et al. Pharmacokinetic interaction of digoxin with an herbal extract from St. John’s wort (Hypericum perforatum). Clin Pharmacol Ther 1999;66:338–45.

19. Holt GA. Food & Drug Interactions. Chicago: Precept Press, 1998, 93.

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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 pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2003.