Does Eating Black Licorice Mimic Melena or Cause It?

Abstract

Purpose: We describe a patient with black tarry stools & an elevated INR after eating a pound of Black Licorice. Although literature describes the effects of Licorice root on the cardiovascular & renal systems, there is a paucity of data on interactions between Black Licorice & warfarin. Furthermore, eating Black Licorice colors stools black & may be mistaken for melena in the absence of true bleeding. Vice versa, the patient with true melena may be falsely reassured that the stools are black because of the Licorice. Methods: An 80-year-old woman with atrial fibrillation anti-coagulated with warfarin ate a pound of Black Licorice 4 days prior to presentation. She then noted black tarry stools but did not seek medical attention because she attributed this to the Licorice. Eventually she developed dizziness, subsequently collapsed & was brought into the Emergency department. There was no hematemesis or abdominal pain. Warfarin had been dosed at 1 mg daily. She had maintained a therapeutic INR, checked weekly for a long time. She was hypotensive & tachycardic, Hematocrit was 14 (baseline 34) & INR 5.5 (baseline 12 days prior was 2.1). The patient had a similar episode related to Black Licorice ingestion in 2004, when she was admitted with black stools & weakness. INR was 9.1 & hematocrit was 16 at that time. She received fresh frozen plasma & packed red blood cells & underwent upper endoscopy. A prepyloric gastric ulcer with a visible vessel at the base was seen & 2 clips were placed. She had an uneventful hospital course & was discharged with a stable hematocrit & therapeutic INR & instructions to avoid Black Licorice. Results: Black Licorice is derived from the root of the plant, Glycyrrhiza glabra & is known for its anti-inflammatory & mineralocorticoid inducing properties. Licorice has also been implicated for interacting with a number of medicines, e.g. digoxin, thiazides & spironolactone. Gliabridin present in Licorice inhibits the P450 system which metabolizes Warfarin. Glycyrrhizin, also present in licorice, is a thrombin inhibitor & prolongs fibrinogen clotting times. Hence, the anti-thrombotic activity & inhibition of warfarin metabolism may synergistically amplify anti-coagulation. Conclusion: Black licorice is a commonly available food product. This case report illustrates how Black Licorice may potentiate or cause GI bleeding especially in patients on warfarin. The presence of Black Licorice in stool can obviously mimic melena & confound its clinical presentation. Therefore, till more data is available, health care providers should caution patients who are at risk for bleeding or on warfarin to avoid black licorice.