Tannins are a group of unrelated chemicals that give plants an astringent taste. Herbs containing high amounts of tannins may interfere with the absorption of ephedrine or pseudoephedrine taken by mouth. Herbs containing high levels of tannins include green tea, black tea, uva ursi (Arctostaphylos uva-ursi), black walnut (Juglans nigra),red raspberry (Rubus idaeus), oak (Quercus spp.), and witch hazel (Hamamelis virginiana).
- Brinker F. Interactions of pharmaceutical and botanical medicines. J Naturopathic Med 1997;7(2):14-20.