St. John's wort (Hypericum perforatum) and warfarin: Dangerous liaisons!

An 85-year-old male patient with a history of hypertension, old anterior wall myocardial infarction and atrial fibrillation was placed on warfarin one year previously. However, he did not comply with regular international normalized ratio (INR) measurements, but kept taking warfarin (5 mg) on a daily basis for almost a year without any problems. After watching a television program about herbal remedies, he decided to take St John’s wort on his own initiative. One month later, he reported to the emergency service of our hospital with upper gastrointestinal bleeding. Initial blood work revealed hemoglobin (Hb): 7.9 g/dl, hematocrit (htc): 23%, and INR: 6.2. With supportive treatment of fresh frozen plasma and blood transfusions, the bleeding ceased. Later, an esophagogastroduodenoscopy showed no significant pathology. The patient was instructed not to use herbal remedies with prescription medications on discharge.