Absorption of ferrous citrate, an iron compound that is usually well absorbed, is reduced in individuals taking hyoscyamine;1 therefore, these two substances should not be taken at the same time.
Tannins are a group of unrelated chemicals that give plants an astringent taste. Herbs containing high amounts of tannins, such as green tea (Camellia sinensis), black tea, uva ursi (Arctostaphylos uva-ursi), black walnut (Juglans nigra), red raspberry (Rubus idaeus), oak (Quercus spp.), and witch hazel (Hamamelis virginiana), may interfere with the absorption of atropine taken by mouth.2
The herb Anisodus tanguticus contains a chemical that has effects similar to atropine, a compound related to hyoscyamine.3 Though no human studies have investigated a possible adverse interaction between hyoscyamine and anisodus, individuals should avoid the combination until more is known.
1. Orrego-Matte H, Fernandez O, Mena I. Effect of anticholinergic agents on the intestinal absorption of 59 Fe ferrous citrate. Am J Dig Dis 1971;16:789–95.
2. Brinker F. Herb Contraindications and Drug Interactions. Sandy, OR: Eclectic Institute, 1997, 100.
3. Qicheng F. Some current study and research approaches relating to the use of plants in the traditional Chinese medicine. J Ethnopharmacol 1980;2:57–63.
Last Review: 05-01-2013
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