Digitalis

Common Names: Purple Foxglove, Foxglove

Clinical Names: Digitalis purpurea, Digitalis lanata

Summary

botanical names: Digitalis purpurea, Digitalis lanata

common name: Foxglove.

overview of interactions:
• commentary: The number of drug interactions, both pharmacokinetic and pharmacodynamic, known to occur with purified cardiac glycosides is large, and increasing. While by logical extension these would also apply to Digitalis extracts, the use of herbal extracts of Digitalis spp. as a primary means of digitalizing cardiac patients has been replaced with the use of pharmaceutical agents. For detailed discussion of primary use of herbal cardiac glycosides in cardiology see the account in Herbal Medicine by RF Weiss. For interactions with digoxin, see Digoxin topic.

overview of interactions:
• herbal synergy: Herb Group Cardiovascular: Glycoside-containing Herbs

• herb affecting drug toxicity: Digoxin

• drug affecting herb toxicity: Loop Diuretics, Thiazide Diuretics

AHPA Botanical Safety Rating: 3




Clinical

botanical names: Digitalis purpurea, Digitalis lanata

common name: Foxglove; Purple Foxglove.

part used: Herb.

affinities: Heart.

actions: Positive inotropic cardiac agent; antiarryhthmic cardiotonic.

dosage:
• tincture: 5 - 10 drops.
• powder: 0.1 mg after meals
(Weiss RF, 130.)

specific indications: Weak, rapid, and irregular heart action, with low arterial tension; broken compensation; weak, rapid, flaccid pulse; weak heart sounds; dusky countenance, with dyspnea, cough, jugular fullness, and weak cardiac action; edema, anasarca, or ascites, with scanty supply of dark-colored urine, with weak heart action; renal congestion; irritable heart with weak action; heart made to beat rapidly but feebly by slight excitement; continuous labored breathing with weak pulsation; renal and cardiac dropsy; desquamative nephritis, with weak heart; capillary hemorrhage; poisoning by aconite, muscarine, or the nitrites.
(Felter HW, Scudder JK, 333.)

therapy:
• Increases the force of contraction of the heart; slows down the heart rate; decreases conduction in the atrioventricular bundle.
(Weiss RF, 130.)
• Dilated heart with mitral incompetence; mitral stenosis and regurgitation; dilated right heart with tricuspid incompetence; debility of the cardiac muscle; increases the power of the auricles and the ventricles to empty themselves; controls fibrillation by inhibiting conductivity
(Felter HW, Scudder JK, 340.)

AHPA Botanical Safety Rating: 3

toxicity:
• Due to narrow therapeutic range of the cardiac glycosides, Digitalis extracts should not be used unless of known (assayed) cardiac glycoside content, and then only by practitioners qualified and experienced in their use. Digitalis is a restricted herb in several countries. In the USA extracts are not available in general commerce, but can be obtained from professional suppliers. Labelling restrictions are in force.
(Brinker F. 1998, 161-162; McGuffin M, et al. 1997, 138-141)

• Contamination of commercial crude herb with Digitalis has been reported. Recently, the FDA recalling several products after herb teas containing Plantain caused side effects attributable to Digitalis contamination. One study analyzed several herbal teas and found digitalis like factors present in small concentrations in several samples, particularly those containing Asclepias tuberosa (Pleurisy Root).
(Longerich L, et al. Clin Invest Med 1993 Jun;16(3):210-218.)

contraindications:
• Ventricular fibrillation
• Digoxin hypersensitivity
(Hardman J, et al. 1996.)

constituents: Cardenolides, glycosides, anthraquinones, flavonoids and saponins



Interactions

herb affecting drug toxicity: Digoxin

• mechanism: Cardiac glycoside-containing herbs will additively synergize with digoxin and related drugs.

• herbal concern: Individuals with cardiac conditions who are using digoxin should not use Digitalis or other glycoside-containing plants at the same time or in proximity, due to the inherently narrow therapeutic index of these compounds.


drug affecting herb toxicity: Loop Diuretics, Thiazide Diuretics

• mechanism: Diuretic-induced perturbations of potassium homeostasis may affect the toxicity of cardiac glycoside-containing herbs.

• herbal concern: Digitalis and cardiac glycoside-containing herbs should not be used while taking potassium-depleting diuretics.


herbal synergy: Herb Group Cardiovascular: Glycoside-containing Herbs

• mechanism: By their additive effects, cardiac glycosides from plants in this group can produce cardiac toxicity when used with Digitalis glycosides such as digoxin or digitoxin or similar medicines. They should never be taken by anyone without the supervision of a physician or qualified herbalist experienced in their use, and they should never be combined with digoxin.

Common herbs containing cardiac glycosides:
• Asclepias tuberosa (Pleurisy Root) *
• Convallaria majalis (Lily of the Valley)
• Scrophularia nodosa (Figwort) *
• Urginea maritima (Squill bulb)

* These herbs contain therapeutically insignificant quantities of glycosides.

Restricted or unusual herbs containing cardiac glycosides:
• Adonis vernalis (Pheasant’s Eye)
• Apocynum cannabinum (Canadian Hemp Root) *
• Helleborus niger (Black Hellebore)*
• Helleborus viride (Christmas Rose) *
• Nerium oleander (Rose Laurel) *
• Strophanthus spp. (Ouabain, Kombe) *
• Thevetia nerifolia (Yellow Oleander) *
* toxic

• herbal support: Medical herbalists use the less toxic Convallaria (Lily of the Valley) in combination with cardiotonics such as Crataegus spp. (Hawthorn) to assist patients desiring to cease digoxin therapy, in a tapered withdrawal protocol.

Please read the disclaimer concerning the intent and limitations of the information provided here.
Do not rely solely on the information in this article.

The information presented in Interactions is for informational and educational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, case reports, and/or traditional usage with sources as cited in each topic. The results reported may not necessarily occur in all individuals and different individuals with the same medical conditions with the same symptoms will often require differing treatments. For many of the conditions discussed, treatment with conventional medical therapies, including prescription drugs or over-the-counter medications, is also available. Consult your physician, an appropriately trained healthcare practitioner, and/or pharmacist for any health concern or medical problem before using any herbal products or nutritional supplements or before making any changes in prescribed medications and/or before attempting to independently treat a medical condition using supplements, herbs, remedies, or other forms of self-care.


References

Bradley PR, ed. British Herbal Compendium, vol 1. Bournemouth, Dorset, UK: British Herbal Medicine Association, 1992.

Brinker F. Herb Contraindications and Drug Interactions. Second edition. Sandy, OR: Eclectic Institute Inc, 1998.

Ellis MD. Dangerous Plants, Snakes, Arthropods, And Marine Life. Hamilton, IL: Drug Intelligence Publications, Inc, 1975.

Felter HW, Scudder JK. The Eclectic Materia Medica, Pharmacology and Therapeutics. Cincinnati, Ohio, 1922. Reprinted Portland, OR: Eclectic Medical Publications, 1985.

Hardman J, et al. (eds.) Goodman and Gilman's Pharmacological Basis of Therapeutics. Ninth Edition. McGraw Hill, 1996.

Longerich L, Johnson E, Gault MH. Digoxin-like factors in herbal teas. Clin Invest Med 1993 Jun;16(3):210-218.
Abstract: Forty-six commercially packaged teas and 78 teas prepared from purchased herbs were assayed for digoxin-like factors (DLF) by their crossreactivity with digoxin antibody (immuno-crossreactive DLF) and by their inhibition of ouabain binding to membrane Na,K-ATPase (NKA inhibitory DLF). Three packaged teas and 3 herbs gave NKA inhibitory DLF values > 30 micrograms digoxin equivalents/cup. Two packaged teas and 3 herbs gave immuno-crossreactive DLF values > .050 micrograms digoxin equivalent/cup. One herb, pleurisy root, had a crossreactive DLF value of 187 micrograms/cup and NKA inhibitory DLF equivalent to 3658 micrograms/cup. Plasma digoxin-like factors were measured after ingestion of the 3 commercially packaged herbal teas with highest values for NKA inhibitory DLF. After ingestion of each of the 3 teas, plasma NKA inhibitory DLF increase, in one case more than 100-fold. Two teas produced a measurable increase in plasma immuno-crossreactive DLF after ingestion. Some digoxin-like factors in human plasma may have a dietary source.

McGuffin M, et al. (eds.) AHPA Botanical Safety Handbook . CRC Press, 1997.

Thienes CH, Haley TJ. Clinical Toxicology. 5th ed. Philadelphia: Lea and Febiger, 1975.

Weiss RF. Herbal Medicine. Beaconsfield, England. Beaconsfield Publishers Ltd., 1988.