Warfarin with Lycium Interaction Details

Brand Names Associated with Warfarin

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated Nov 07, 2023

Interaction Effect

Increased risk of bleeding

Interaction Summary

Four cases of increased INR, two with associated bleeding, have been reported with coadministration of warfarin with Lycium barbarum (gogi berry) tea or wine. Avoidance of Lycium barbarum during warfarin therapy is advised . If a patient chooses to use warfarin concomitantly with traditional Chinese medicines, such as Lycium barbarum, increased monitoring of INR is recommended .

Severity

Major

Onset

Unspecified

Evidence

Probable

How To Manage Interaction

Avoid concurrent use of Lycium barbarum and warfarin. If a patient chooses to use warfarin concomitantly with traditional Chinese medicines, such as Lycium barbarum, monitor the INR more frequently , as the risk for bleeding is increased with coadministration.

Mechanism Of Interaction

Unknown

Literature Reports

A) A 61-year-old Chinese woman stabilized for approximately 3 years on warfarin for atrial fibrillation had an elevated INR of 4.1 at a clinic visit, with no signs or symptoms of bleeding complications. Her INR previously ranged from 2 to 3 with a weekly warfarin dose of 18 to 19 mg. Other medications included benazepril, atenolol, digoxin, and fluvastatin. She reported drinking a tea made from dried Lycium barbarum fruit (goji berries), approximately 6 ounces 3 to 4 times daily for 4 days prior to the clinic visit. The Lycium barbarum tea was discontinued and warfarin was withheld for one day. Warfarin was restarted at a lower dose, then titrated to her previous maintenance dose of 19 mg/week. Her INR values ranged from 2 to 2.5 during this period. Application of the Naranjo scale indicated that the elevated INR was probably related to the use of Lycium barbarum in this patient. An in vitro evaluation showed Lycium barbarum inhibited warfarin CYP2C9 metabolism, with a dissociated constant (Ki) of 3.4 mg/mL. Since the inhibition observed was weak, other possible mechanisms may be responsible for the interaction, including effects on warfarin absorption, p-glycoprotein, or an anticoagulant effect of the herb itself .

B) A case report described an elevated INR in an 80-year-old Chinese woman following concomitant use of warfarin and Lycium barbarum (goji berries). Her medications included nifedipine, glibenclamide, metformin, lorazepam, and a titrated dose of warfarin (between 15.5 mg and 16 mg/week). An INR between 2.05 and 3.56 was maintained over a 6-month monitoring period. The INR increased to 4.97 during the seventh month of monitoring. Prior to testing, the patient reported having consumed an estimated 50 g of Lycium barbarum over a 2-day period in a concentrated herbal tea. Her dose of warfarin was withheld for 2 days, restarted at a reduced dose of 14 mg/week, and she maintained a stable INR for 2 months. Subsequent re-consumption of an estimated 40 g of Lycium barbarum in a tea the day prior to testing led to an INR of 3.86. Again, warfarin was withheld for 2 days and was restarted at the 14 mg weekly dosage. The patient was asked not to use herbal tea and her INR remained stable for the next 6 months .

C) A 71-year-old woman experienced bleeding and bruising 4 days after concomitant use of Lycium barbarum (goji berry juice) and warfarin. Three months prior to presentation, the patient started treatment with warfarin 1.5 mg/day for VTE prophylaxis after undergoing knee surgery. Beginning 4 days prior to presentation, the patient consumed 30 mL of goji juice each morning and evening. Her other medications included ezetimibe, lisinopril, famotidine, meclizine, alprazolam, and diphenhydramine. On the fourth day of Lycium barbarum and warfarin coadministration, she developed epistaxis, bruising, and rectal bleeding, which caused her to immediately discontinue use of the Lycium barbarum. Upon presentation to the emergency department, her INR was found to exceed the upper limit for INR calculation and her prothrombin time was greater than 120 seconds. After the patient was treated with phytonadione 5 mg, her INR declined to 7.5 the following day, at which time the phytonadione dose was increased to 10 mg. On the third day of hospitalization, her INR declined further to 2.6 and she received a final dose of phytonadione 10 mg. The patient was discharged with no further bleeding observed or any other complications. The Naranjo score for INR elevation and related bleeding in this patient was 6, indicating a probable relationship between the events and the concomitant use of Lycium barbarum and warfarin .

D) A 65-year-old Chinese man experienced hematuria the following morning after coadministration of Lycium barbarum (goji berry wine) and warfarin. The patient had been maintained on warfarin 1.875 mg/day as anticoagulant therapy for 2 years following a prosthetic heart valve replacement and his INR was stable in the normal range (1.7 to 2.5). In the evening prior to presentation, he consumed 20 mL of goji berry wine and was taking no other medications. The patient developed macroscopic hematuria the next morning and went to the hospital. Test results showed a urinary RBC of 33,202/mcL (normal, 0 to 23/mcL) and an INR of 3.84. The goji wine was discontinued and warfarin therapy was interrupted for 2 days. The hematuria continued for 1 day. Two days after presentation, the patient had an INR of 2.12 and urine test results were normal, with a urinary RBC of 11/mcL. He was restarted on warfarin 1.875 mg/day and after 1 week, his INR was 2. The Naranjo score for elevated INR with hematuria in this patient was 6, indicating a probable relationship between the events and the concomitant use of Lycium barbarum and warfarin .

Warfarin Overview

• Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic (replacement or mechanical) heart valves, and people who have suffered a heart attack. Warfarin is also used to treat or prevent venous thrombosis (swelling and blood clot in a vein) and pulmonary embolism (a blood clot in the lung). Warfarin is in a class of medications called anticoagulants ('blood thinners'). It works by decreasing the clotting ability of the blood.

Return To Our Drug Interaction Homepage

Feedback, Question Or Comment About This Information?

Definitions

Severity Categories

Contraindicated

These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.

Major

This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.

Moderate

This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.

Minor

While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.

Onset

Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.

Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.

Evidence

Level of documentation of the interaction.

Established: The interaction is documented and substantiated in peer-reviewed medical literature.

Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.

How To Manage The Interaction

Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.

It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.

Mechanism Of Interaction

The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.

Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.

Where Does Our Information Come From?

Information for our drug interactions is compiled from several drug compendia, including:

• Gold Standard Drug Database
• Micromedex
• Lexicomp
• DrugBank

The prescribing information for each drug, as published on DailyMED, is also used. 

Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.

The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.