*St. John’s wort should not be taken by organ transplant recipients, as it may cause organ rejection.
*In one small study, St. John’s wort was associated with elevated thyroid stimulating hormone (TSH) levels.
* DRUG INTERACTIONS : One of the major downsides of using St. John’s wort is that it may interact in a potentially harmful way with many common medications. It's broken down in the liver by enzymes that also process certain medications. The result is that it can decrease the effectiveness of other medications a person is taking or increase the effect, leading to an increased risk of adverse effects. Avoid taking the following with St. John's wort:
**Alcohol
**Allergy drugs, such as Allegra (fexofenadine)