Digoxin is a cardiac glycoside from a plant, foxglove (Digitalis lantana.) It slows the pulse and increases the strength of contraction of cardiac muscle. The high therapeutic range of the dose of digoxin is close to the lower toxic range. Therefore, monitoring blood levels is necessary to avoid side effects. Hypokalemia (low potassium,) hypomagnesemia (low magnesium,) kidney failure and hypothyroidism increase the risk of toxicity to digoxin.
Hawthorn (Crataegus spp.) is an herb used, historically, to treat heart disease, hypertension, hyperlipidemia and congestive heart failure. Many people who take digoxin take hawthorn, also. Hawthorn herb preparations are widely available. Hawthorn contains alkaloid chemicals related to digoxin. The authors studied the ability of hawthorn to interfere with the testing of digoxin levels and the possibility of drug-herb interactions.
Hawthorn contains the following flavonoids: epicatechin, chlorogenic acid, isoquercitin and hyperoside.
Hawthorn was found to interfere with some, but, not all, chemical tests for digoxin. Some brands of hawthorn interfered more than others. (The same was found to be true for ashwagandha and ginseng.) Hawthorn increases intracellular levels of calcium. Both, digoxin and hawthorn may bind to the same site on Na+/K+-ATPase and do not have additive effects.
CONCLUSION: Patients who are having blood tests for digoxin should inform the laboratory when they are taking hawthorn. Hawthorn can appear on some tests for digoxin and may interact with digoxin. “…a patient receiving digoxin should avoid hawthorn.”
NOTE: People who prefer more natural products, such as hawthorn, ashwagandha or ginsengs, should use digoxin with caution.
Chlorogenic acid is believed to be responsible for the reduced risk of diabetes mellitus seen in heavy coffee drinkers. A green coffee bean extract is available.