Tamoxifen herb interactions. It is unknown whether the concurrent use of tamoxifen and . . . . . Herb/Nutraceutical: Avoid black cohosh, dong quai in estrogen . know if you're also taking other drugs, including phenytoin (Dilantin), tamoxifen . . . . . Food: Avoid grapefruit juice (may decrease the metabolism of tamoxifen). There has been at least one report of an interaction . . Tamoxifen Herb InteractionsWhat Are Depletions & Interactions? A to Z Index of Vitamin & Herb Interactions ... more