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.

Supplementation Possibly Helpful

Although the evidence is quite weak, digoxin might cause a tendency toward calcium deficiency.6 Taking calcium supplements could not hurt.

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.16.

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.

Possible Interaction

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 Dangerous Interaction

Because horsetail can deplete the body of potassium, it may not be safe to combine this herb with digitalis drugs.10

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.

No Interaction

One study found that simulataneous use of the herb Ginkgo biloba (80 mg three times daily of the typical standardized extract) does not change digoxin levels.15