LETTER TO THE EDITOR
Interaction of herbal drugs with digoxin
Tsung O. Cheng, MD, FACC*
* Department of Medicine, The George Washington University Medical Center, 2150 Pennsylvania Avenue NWWashington, DC 20037, USA
I enjoyed reading the recent study by Valli and Giardina (1) on drug interactions of herbal therapies with cardiovascular effects. It was quite comprehensive. However, I would like to make some additional comments on the interaction of herbal drugs with digoxin.
Numerous herbs containing cardiac glycosides have been identified as containing digoxin-like substances, including milkweed, lily of the valley, Siberian ginseng, and hawthorne berries (2). Ginseng may falsely elevate digoxin levels (2). A Chinese herb called kushen has digoxin-like properties (3). Another Chinese medicine, which is very popular in Japan (4) and is called kyushin ("to save the heart"), has been documented to crossreact with digoxin assays (5,6). It was determined that one tablet of kyushin has a digoxin-like immunoreactivity equivalent to 1.9 µg (TDX analyzer; Abbott Laboratories, North Chicago, Illinois) and 72 µg (Enzymun-Test; Boehringer, Mannheim, Germany) of digoxin (5,6).
Many other Chinese medicines contain chan-su, which is a component of kyushin (4). Thus, patients with spuriously elevated digoxin levels without associated signs and symptoms of digoxin toxicity should be questioned regarding herbal therapies. Finally, licorice, opium, and St. John’s wort may all increase the risk of digoxin toxicity (7).
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References
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1. Valli G, Giardina E-GV. Benefits, adverse effects and drug interactions of herbal therapies with cardiovascular effects. J Am Coll Cardiol. 2002;39:1083–1095[Abstract/Free Full Text]
2. Miller LG. Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions. Arch Intern Med. 1998;158:2200–2211[Abstract/Free Full Text]
3. Huang KC. The Pharmacology of Chinese Herbs. 2nd edition. Boca Raton, FL: CRC Press; 1999. 69–72
4. Fushimi R, Koh T, Iyama S, et al. Digoxin-like immunoreactivity in Chinese medicine. Ther Drug Monit. 1990;12:242–245[Medline]
5. Fushimi R, Tachi J, Amino N, Miyai K. Chinese medicine interfering with digoxin immunoassays. Lancet. 1989;1:339[Medline]
6. Cheng TO. Herbal interactions with cardiac drugs. Arch Intern Med. 2000;160:870–871[Free Full Text]
7. Fetrow CW, Avila JR. Professional’s Handbook of Complementary and Alternative Medicines. 2nd edition. Springhouse, PA: Springhouse Publishing; 1999. 708–11
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