Foxglove

Description

Foxglove is three to six feet high, with ovate to lance-shaped, soft-hairy, toothed, leaves up to one foot long in a basal rosette.  The purple to white, spotted, thimble-shaped flowers are 1.25 inches long, in spikes.  It can be identified in the summer (Foster 1990).   D. lanata has long, narrow leaves and smaller, yellow-brown flowers. Foxgloves are commonly cultivated as ornamentals in North America.

History

Foxglove is indigenous to western and central Europe. In Ireland, the ancient Druids and the 13th-century Physicians of Myddvai in Wales were said to have used feverfew. The Dodoens, in 1544, used a potion of feverfew and wine as an expectorant, a remedy that poisoned many people. Foxglove was included in the London Pharmacopoeia in 1650. It was apparently introduced to New England by the mid-eighteenth century (Le Strange 1977).

Foxglove has been used to treat dropsy (an obsolete term for generalized edema, or swelling) since at least the 16th century (Griggs 1981).  In 1785, William Withering, an English doctor who became interested in botany after falling in love with a woman who painted flowers, learned about an herbal treatment for dropsy from an unnamed “old woman from Shropshire”. Withering determined that the active compound in the mixture was foxglove and proceeded to experiment with it, first in turkeys, and later in humans, with good results (Griggs 1981). Digitalis glycosides remain a valuable therapeutic today.

Foxglove has also been used as a diuretic, and as a treatment for asthma, edema, or palpitations. Historically, ointments were made from the leaf as a remedy for indurations and tumors (Duke 2001).

Current Medicinal Uses

Foxglove is one of the few herbs used in pharmaceutical manufacture today; the digitalis glycosides commonly used to treat congestive heart failure or atrial fibrillation are difficult to synthesize, so are easier to derive directly from foxglove. Digitoxin can be obtained from either D. purpurea or D. lanata; digoxin is present only in the leaves of D. lanata, the species most commonly used in pharmaceutical manufacture(Fugh-Berman 2003).

Digitalis glycosides inhibit sodium-potassium ATPase, increasing intracellular sodium and stimulating sodium calcium exchange. The net effect is a positive inotropic effect (an increase in the force of systolic contractions) and a vagomimetic effect, which slows the heart rate (Fugh-Berman 2003).

Adverse Effects

Overdoses of digitalis alkaloids can cause vomiting, diarrhea, bradycardia, atrioventricular heart block, confusion, and visual disturbances (Fugh-Berman 2003). Foxglove has caused serious poisonings, and anti-digoxin Fab fragments are not particularly effective in treating foxglove poisoning. Most cases of toxicity have been caused by wild-food gatherers mistaking the plant for comfrey (Porter 1999, Colls 1999, Bain 1985).

An apparently accidentally adulterated mixture of herbs meant for “internal cleansing” (a code phrase for laxative effects) resulted in two cases of digoxin poisoning (Slifman 1998). 

References

Bain, RJI.  Accidental digitalis poisoning due to drinking herbal tea.  BMJ 1985;290:1624

Colls BM.  A salutary lesson: three very unwise men.  BMJ 1999;318:1729.

Duke JA. Handbook of Medicinal Herbs. CRC Press, Boca Raton, 2001.

Foster S, Duke JA. Eastern/Central Medicinal Plants. Houghton Mifflin Company, Boston, 1990.

Fugh-Berman A. The 5-Minute Herb and Dietary Supplement Consult. Lippincott, Williams, and Wilkins, Baltimore, 2003:138-139.

Griggs B. Green Pharmacy: the history and evolution of Western herbal medicine. Healing Arts Press, Rochester VT:1981:143-146..

Le Strange, R. A History of Herbal Plants. Arco Publishing Company, Inc., New York, 1977.

Lewis WH, Elvin-Lewis MPF. Medical Botany: Plants Affecting Man’s Health. John Wiley & Sons, Inc., New York, 1977.

Porter R, Schultz D, Robertson WO.  Alternative medicine toxicity: digitalis poisoning!  J Tox Clin Tox 1999:37(5):Abstract 83.

Rich SA, Libera JM, Locke RJ.  Treatment of foxglove extract poisoning with digoxin-specific Fab fragments.  Ann Emerg Med 1993;22(12):1904-1907.

Slifman NR, Obermeyer WR, Musser SM et al.  Contamination of botanical dietary supplements by Digitalis lanata.  NEJM 1998;339:806-811.

Disclaimer 

Information on this website is for educational purposes only. Many herbs historically used for medicine are considered too toxic to use today; some of these herbs have caused deaths. Do not ingest these herbs based on information on this website. We have not provided sufficient information for the safe medicinal use of any of these herbs, nor sufficient information for treatment of poisoning. All recreational use of these herbs is dangerous.