What is digoxin? How does it interact with other drugs?

Magnesium

Effect: Supplementation Possibly Helpful, but Take at a Different Time of Day

Magnesium deficiency can increase the risk of toxicity from digoxin. However,
taking magnesium supplements at the same time as digoxin might
impair the absorption of the drug. One should not take the magnesium supplement
during the two hours before or after using digoxin.

Calcium

Effect: Supplementation Possibly Helpful

Although the evidence is quite weak, digoxin might cause a tendency toward
calcium deficiency. Taking calcium supplements can be helpful.

Hawthorn

Effect: Possible Interaction

The herb hawthorn is used to treat congestive heart failure. Whether
it is safe to combine hawthorn with digoxin remains unclear. One small study
failed to find any harmful interaction, but more research must be done before
reliable conclusions can be drawn.

Licorice

Effect: Possible Dangerous Interaction

Licorice root can lower potassium levels in the body, which can be dangerous for a person taking digoxin. The special form of licorice known as DGL (deglycyrrhizinated licorice) is a deliberately altered form of the herb that should not affect potassium levels.

Eleutherococcus senticosus

Effect: Possible Interaction

There has been one report of an apparent elevation in digoxin level caused by the herb Eleutherococcus senticosus (also known as Siberian ginseng). 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.

Horsetail

Effect: Possible Dangerous Interaction

Because horsetail can deplete the body of potassium, it may not be
safe to combine this herb with digitalis drugs.

St. John’s Wort

Effect: 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.
Conversely, persons taking St. John’s wort and whose digoxin dose is adjusted by
their physician should note that suddenly stopping the herb could cause blood
levels of the drug to rise dangerously high.

Uzara

Effect: 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. These substances also might alter (either increase or decrease) the effectiveness of digoxin.

Ginkgo biloba

Effect: No Interaction

One study found that simultaneous use of the herb Ginkgo biloba (80 milligrams three times daily of the typical standardized extract) does not change digoxin levels.

Bibliography

Gurley, B. J., 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.” Molecular Nutrition and Food Research 52, no. 7 (2008): 772-779.

Mauro, V. F., et al. “Impact of Ginkgo biloba on the Pharmacokinetics of Digoxin.” American Journal of Therapeutics 10 (2003): 247-251.

Mueller, S. C., et al. “Effect of St John’s Wort Dose and Preparations on the Pharmacokinetics of Digoxin.” Clinical Pharmacology and Therapeutics 75 (2004): 546-557.

Pronsky, Z. M., and J. P. Crowe. Food Medication Interactions. 16th ed. Birchrunville, Pa.: Food-Medication Interactions, 2010.

Tankanow, R., et al. “Interaction Study Between Digoxin and a Preparation of Hawthorn (Crataegus oxyacantha).” Journal of Clinical Pharmacology 43 (2003): 637-642.

Thurmann, P. A., et al. “Interference of Uzara Glycosides in Assays of Digitalis Glycosides.” International Journal of Clinical Pharmacology and Therapeutics 42 (2004): 281-284.