It is recommended to wait at least 5 days after stopping an antidepressant before trying St. John's Wort to ensure the complete elimination of the previous medication from your body. The standard recommended dosage is normally 300 mg of standardized extract three times a day with meals. It may take a few weeks to feel the effects of the therapy. If you do not see improvement with St. John's Wort, it is advisable to discuss other treatment options with your doctor.