Case report: Cranberry juice and warfarin

Warfarin and food, herbal or dietary supplement interactions: A systematic review

AIMS

To present an updated overview on the safety of concurrent use of food, herbal or dietary supplement and warfarin.

METHODS

A systematic literature review was performed on 5 databases from inception up to 31 December 2019. These interactions were classified depending on the likelihood of interaction and supporting evidences.

RESULTS

A total of 149 articles describing 78 herbs, food or dietary supplements were reported to interact with warfarin. These reports described potentiation with 45 (57.7%) herbs, food or dietary supplements while 23 (29.5%) reported inhibition and 10 (12.8%) reported limited impact on warfarin pharmacokinetics and pharmacodynamics. Twenty unique herb and dietary supplements also reported to result in minor bleeding events, such as purpura and gum bleeding as well as major events such as intracranial bleeding that led to death.

CONCLUSION

While most food, herbs and supplements can be safely taken in moderation, healthcare professionals should be aware of the increased risk of bleeding when taking several food and herbs. These include Chinese wolfberry, chamomile tea, cannabis, cranberry, chitosan, green tea, Ginkgo biloba, ginger, spinach, St. John's Wort, sushi and smoking tobacco. Patients should be counselled to continue to seek advice from their healthcare professionals when starting any new herbs, food or supplement.

Cranberry and recurrent cystitis: more than marketing?

Epidemiologic studies indicate that millions of people suffer from recurrent cystitis, a pathology requiring antibiotic prophylaxis and entailing high social costs. Cranberry is a traditional folk remedy for cystitis and, which, in the form of a variety of products and formulations has over several decades undergone extensive evaluation for the management of urinary tract infections (UTI). The aim of this retrospective study is to summarize and review the most relevant and recent preclinical and clinical studies on cranberries for the treatment of UTIs. The scientific literature selected for this review was identified by searches of Medline via PubMed. A variety of recent experimental evidence has shed light on the mechanism underlying the anti-adhesive properties of proanthrocyanidins, their structure-activity relationships, and pharmacokinetics. Analysis of clinical studies and evaluation of the cranberry efficacy/safety ratio in the prevention of UTIs strongly support the use of cranberry in the prophylaxis of recurrent UTIs in young and middle-aged women. However, evidence of its clinical use among other patients remains controversial.

A Comprehensive Review of Potential Warfarin-Fruit Interactions

Purpose:

The aim of this review is to discuss possible interactions that may occur between warfarin and fruit products.

Methods:

A literature search was conducted using the search terms: “warfarin (Coumadin®) and fruit interactions, warfarin and fruit, warfarin and fruit juice, case reports and clinical trials”.

Results:

A total of 23 citations (15 case reports and 7 controlled clinical trials) were reviewed. The majority of cases involved cranberry products, while pomegranate juice, avocado, grapefruit juice, mango, and papain were also implicated in reports of suspected warfarin-fruit interactions. Cranberry juice was also the most frequently studied fruit product. Other fruit products evaluated with warfarin in controlled clinical trials were cranberry concentrate and grapefruit juice.

Conclusion:

Although a number of case reports have been published that suggest warfarin has the potential to interact with several fruit products, it is difficult to determine their relevance, as scientific evidence is scarce. Until further information is available, clinicians may want to encourage patients to consume cranberry products and grapefruit juice in small to moderate quantities and to inquire about the recent consumption of mangos, pomegranate juice, and avocados when taking a dietary history or when assessing possible causes for international normalized ratio (INR) instability.

An overview of the evidence and mechanisms of herb-drug interactions

Despite the lack of sufficient information on the safety of herbal products, their use as alternative and/or complementary medicine is globally popular. There is also an increasing interest in medicinal herbs as precursor for pharmacological actives. Of serious concern is the concurrent consumption of herbal products and conventional drugs. Herb-drug interaction (HDI) is the single most important clinical consequence of this practice. Using a structured assessment procedure, the evidence of HDI presents with varying degree of clinical significance. While the potential for HDI for a number of herbal products is inferred from non-human studies, certain HDIs are well established through human studies and documented case reports. Various mechanisms of pharmacokinetic HDI have been identified and include the alteration in the gastrointestinal functions with consequent effects on drug absorption; induction and inhibition of metabolic enzymes and transport proteins; and alteration of renal excretion of drugs and their metabolites. Due to the intrinsic pharmacologic properties of phytochemicals, pharmacodynamic HDIs are also known to occur. The effects could be synergistic, additive, and/or antagonistic. Poor reporting on the part of patients and the inability to promptly identify HDI by health providers are identified as major factors limiting the extensive compilation of clinically relevant HDIs. A general overview and the significance of pharmacokinetic and pharmacodynamic HDI are provided, detailing basic mechanism, and nature of evidence available. An increased level of awareness of HDI is necessary among health professionals and drug discovery scientists. With the increasing number of plant-sourced pharmacological actives, the potential for HDI should always be assessed in the non-clinical safety assessment phase of drug development process. More clinically relevant research is also required in this area as current information on HDI is insufficient for clinical applications.