A nurse is teaching a client who is to start taking fluoxetine. The nurse should instruct the client that which of the following supplements interacts adversely with fluoxetine?

A. Echinacea may affect immune function but does not have a direct adverse interaction with fluoxetine. B. St. John's wort is known to interact with fluoxetine by increasing the risk of serotonin syndrome, a potentially life-threatening condition. Clients should avoid using St. John's wort with fluoxetine. C. Ginkgo biloba can interact with anticoagulants but does not typically cause a dangerous interaction with fluoxetine. D. Soy protein does not have a known adverse interaction with fluoxetine.