The digitalis drugs digoxin and digitoxin are used for congestive heart failure and other heart conditions. The concerns described below apply equally to both medications.
Supplementation Possibly Helpful, but Take at a Different Time of Day
Magnesium deficiency can increase the risk of toxicity from digoxin.12 However, taking magnesium supplements at the same time as digoxin might impair the absorption of the drug.5 The solution? Do not take your magnesium supplement during the two hours before or after your digoxin dose.
Possible Dangerous Interaction
Licorice root can lower potassium levels in the body, which can be dangerous for an individual taking digoxin.7,8 The special form of licorice known as DGL (deglycyrrhizinated licorice) is a deliberately altered form of the herb that should not affect potassium levels.
There has been one report of an apparent elevation in digoxin level caused by the herb Eleutherococcus senticosus (so-called "Siberian ginseng").9 However, the details of the case suggest that the eleutherococcus product might actually have interfered with a test for digoxin, rather than the digoxin levels themselves.
Possible Reduction of Effectiveness of Drug
Evidence suggests that St. John's wort may interact with digoxin, possibly requiring an increased dosage to maintain the proper effect.11-13,17 Conversely, if you are taking St. John's wort already and your physician adjusts your dose of medication, suddenly stopping the herb could cause blood levels of the drug to rise dangerously high.
Possible Harmful Effect
Uzara root ( Xysmalobium undulatum) is used to treat diarrhea. It contains substances similar to digoxin, and may cause false readings on tests designed to measure digoxin levels.14 These substances also might alter (either increase or decrease) the effectiveness of digoxin.
1. Toffaletti J. Electrolytes, divalent cations, and blood gases (magnesium). Analyt Chem. 63(12): 192R194R, 1991.
2. Whang R, Oei TO, Watanabe A. Frequency of hypomagnesemia in hospitalized patients receiving digitalis. Arch Intern Med. 145: 655656, 1985.
3. Landauer RA. Magnesium deficiency and digitalis toxicity. JAMA. 251: 730, 1984.
4. Cohen L and Kitzes R. Letter. JAMA. 251: 730, 1984.
5. Tatro D (ed.). Drug interaction facts. St. Louis, MO: Facts and Comparisons, 1999: 446.
6. Kupfer S and Kosovsky JD. Effects of cardiac glycosides on renal tubular transport of calcium, magnesium, inorganic phosphate and glucose in the dog. J Clin Invest. 44: 11321143, 1965.
7. Shintani S, Murase H, Tsukagoshi H, and Shiigai T. Glycyrrhizin (licorice)-induced hypokalemic myopathy. Report of two cases and review of the literature. Eur Neurol. 32: 4451, 1992.
8. Pronsky Z (ed.). Powers and Moore's food medication interactions, 10th ed. Pottstown, PA: Food-Medication Interactions, 1997: 49.
9. McRae S. Elevated serum digoxin levels in a patient taking digoxin and Siberian ginseng. Can Med Assoc J.155: 293295, 1996.
10. Brinker F. Herb contraindications and drug interactions, 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998: 85.
11. Maurer A, et al. Interaction of St. John's wort extract with phenprocoumon. Eur J Clin Pharmacol. 55(Abstract 79): A22, 1999.
12. Yue QY, Bergquist C, Gerden B. Safety of St. John's wort ( Hypericum perforatum) [letter]. Lancet. 355: 576577, 2000.
13. Mueller SC, Uehleke B, Woehling H, et al. Effect of St John's wort dose and preparations on the pharmacokinetics of digoxin. Clin Pharmacol Ther. 2004;75:546-57.
14. Thurmann PA, Neff A, Fleisch J, et al. Interference of Uzara glycosides in assays of digitalis glycosides. Int J Clin Pharmacol Ther. 2004;42:281-4.
15. Mauro VF, Mauro LS, Kleshinski JF, et al. Impact of Ginkgo biloba on the pharmacokinetics of digoxin. Am J Ther. 2003;10:247-51.
16. Tankanow R, Tamer HR, Streetman DS, et al. Interaction study between digoxin and a preparation of hawthorn (Crataegus oxyacantha). J Clin Pharmacol. 2003;43:637-42.
17. Gurley BJ, Swain A, Williams DK, et al. Gauging the clinical significance of P-glycoprotein-mediated herb-drug interactions: Comparative effects of St. John's wort, echinacea, clarithromycin, and rifampin on digoxin pharmacokinetics. Mol Nutr Food Res. 2008 Jan 23.
Last reviewed December 2015 by EBSCO CAM Review Board
Last Updated: 12/15/2015
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