Which of the following should be avoided when taking fluoxetine?

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) used primarily to treat depression, anxiety disorders, and other conditions. It can interact with various substances, potentially leading to adverse effects or diminished efficacy.

St. John's Wort is a herbal supplement often used for its antidepressant properties. However, it can significantly affect the metabolism of fluoxetine by inducing certain liver enzymes, particularly CYP3A4. This may lead to reduced levels of fluoxetine in the bloodstream, creating a risk of therapeutic failure or withdrawal symptoms. Moreover, there is a potential for serotonin syndrome, a serious condition resulting from an excess of serotonin, when combining SSRIs with St. John's Wort.

While smoking, alcohol consumption, and grapefruit can also have interactions with various medications, the most significant and direct concern with fluoxetine is associated with St. John's Wort. Therefore, St. John's Wort should be avoided to ensure the effectiveness and safety of treatment with fluoxetine.