Table of Contents

Introduction..............................................................5

How Herbs Can Interfere With Warfarin ................6

Natural Health Products and Interactions With Warfarin

Black Cohosh (Cimicifugaracemosa) ..............7

Boldo and Fenugreek (Peumus boldo andTrigonelle foenum-graecum) ............................8

Chamomile (Matricariarecutita) ....................9

Chitosan ........................................................10

Coenzyme Q10 (Ubiquinone)........................11

Cranberry (Vacciniummacrocarpon) ............12

Curbicin..........................................................13

Danshen (Salvia miltiorrhiza)........................14

Dong Quai (Angelica senensis) ....................15

Echinacea (Echinacea angustifolia, Echinacea pallida, Echinacea purpurea, Purple coneflower) ........................................16

Ephedra/Ma Huang (Ephedra sinica) ............17

Evening Primrose Oil (Oenothera Biennis) ......................................18

Feverfew (Tanacetum parthenium) ................19

Flaxseed (Linum usitatissimum) ....................20

Garlic (Allium sativum)..................................21

Ginger (Zingiber officinale) ..........................22

Ginkgo (Ginkgo biloba) ................................23

Ginseng, Asian (Panax ginseng)....................24

Ginseng, Canadian/American (Panax quinquefolius) ....................................25

TARO-WARFARIN(Warfarin sodium tablets,USP)

1Associate Professor, Faculty of Pharmacy, University of Toronto2Student, Canadian College of Naturopathic Medicine

1mg - Pink

2m g - Lavender

2.5 mg - Green

3 mg -Tan

4 mg - Blue

5 mg - Peach

6 mg - Teal

7.5 mg - Yellow

10 mg - White

Ginseng, Siberian (Eleutherococcus senticosus) ........................26

Glucosamine/Chondroitin ..............................27

Kava (Piper methysticum)..............................28

Mango (Mangifera indica) ............................29

Methyl Salicylate (Oil of wintergreen) ..........30

Milk Thistle (Silybum marianum)..................31

Nettle (Urtica dioica ) ..................................32

Omega 3 Fatty Acids (Fish oils) ....................33

Quercitin ........................................................34

Quilinggao......................................................35

Red Clover (Trifolium pratense) ....................36

Royal Jelly......................................................37

Saw Palmetto (Serenoa repens) ....................38

Soy (Glycine soja, Glycine max) ..................39

St. John's Wort (Hypericum perforatum) ......40

Tea - Black or Green (Camellia sinensis)......41

Vitamin K ......................................................42

Wolf Berry or Goji Berry (Lycium barbarum) ........................................43

Summary ................................................................44

Table of Contents (cont’d) Introduction

The use of natural health products including herbs hasdramatically increased in Canada over the past severalyears. According to recent surveys, up to 50% ofCanadians use natural health products every year.

Although people take herbal products to prevent or treatvarious diseases, there is often little high quality scientificevidence that they are effective. Since January 2004,herbals and other natural supplements have been regulatedas natural health products under new regulationsdeveloped by the Natural Health Products Directorate(Health Canada). The new regulations require that eachproduct be reviewed by Health Canada and given a license(noted on the label as a NPN or Natural Product Number).Manufacturers of natural health products must also belicensed and follow specific “Good ManufacturingPractice” standards as explained in the new regulations.Finally, the new regulations outline what information mustbe provided to consumers on the labels of all naturalhealth products. For more information about the newregulations visit the Natural Health Product Directoratewebsite at:

http://www.hc-sc.gc.ca/dhp-mps/prodnatur/index_e.html

Many natural health products, including herbs, areadvertised as being safe because they are “natural.” Being“natural” does not mean that side effects will not occur orthat herbal products will not interact with medications youmay be taking.

How Herbs Can Interact With Warfarin

Herbs contain hundreds of ingredients,which can cause unwanted side effectsand interact with prescriptionmedications. Although some research hasbeen done on how herbs interact withprescription medications, not enough isknown. That is why you should be cautiousabout taking herbs with warfarin sodium tablets3.

Some herbs can interact with warfarin, causing it to increaseits effectiveness, which may cause bleeding problems. Otherherbs may cause warfarin to be less effective, which maylead to blood clotting problems. Still other herbs preventplatelets from forming a clot after an injury, similar to theway aspirin does. When these products are taken withwarfarin there is a greater chance of excess bleeding.

The purpose of this booklet is to identify some commonherbs and other natural health products, and describe what iscurrently known about how they interact with warfarin. Italso briefly describes some of the common uses, andpossible side effects of these herbs and natural healthproducts. The information presented is based on a review ofthe scientific literature available at the time this booklet wasprepared.

The authors of this booklet do not claim to have reviewed all the literatureand believe there is additional literature that has not come to ourattention. Further, the authors make no judgments as to the truthfulnessof the literature or the accuracy of any claims. The “Purpose/Use” foreach herbal product is based on unsubstantiated claims in literature aswell as historical claims, the truthfulness of which has not been subjectedto rigorous review by the Natural Health Products Directorate (HealthCanada). Such claims are included in this booklet only as a background totheir possible interaction with warfarin.

3 You should always talk to your doctor, pharmacist, and other healthcare providers before youtake any prescription medication, over-the-counter product, or herbal product with warfarin.

5 6

Black Cohosh (Cimicifugaracemosa)

Purpose/Use: Black cohosh isclaimed to relieve hot flashes, mooddisturbances and other symptomsassociated with menopause. Thefew clinical trials completed todate suggest that any positiveeffects are likely to be small. Sideeffects of black cohosh aregenerally mild, but few studies haveinvestigated its use for longer than 6 months.

Interactions with warfarin: Raw black cohosh plants have been reported to contain salicylic acid in small amounts and thustheoretically may increase theeffects of drugs like warfarin. We are not aware of any clinicallyrelevant reports of interactions between black cohosh and warfarin.However, you should always talk to your doctor,pharmacist or other healthcare providers before takingblack cohosh with warfarin.

Chamomile(Matricariarecutita)

Purpose/Use: Chamomilehas a long tradition ofmedicinal use for a widerange of conditions includingsleep disorders, anxiety,infections or inflammation ofthe skin, colic in infants,stomach ailments and teethingpain. However there are veryfew clinical trials assessing thescientific efficacy of chamomile forthese conditions. It appears relatively safe; however, thereare reported cases of allergic reactions from people whoused chamomile medicinally (or came into physicalcontact with the plant) including some that were life-threatening.

Interactions with warfarin: Chamomile is known tocontain a compound (called coumarin) which mayincrease the risk of bleeding. That means that ingestingchamomile together with warfarin may increase your INRand thus your risk of experiencing side effects such asbleeding problems. There are several cases of thishappening to patients. Therefore, talk to your doctor,pharmacist or other healthcare providers before takingchamomile together with warfarin.

7 8 9

Chitosan

Purpose/Use: Chitosan comes from chitin which formsthe exoskeleton of crustaceans such as crabs, lobsters andcrayfish, as well as many insects and spiders. It is used inthe management of high cholesterol and as a dietary fiber.Since it is often made from shellfish, patients withshellfish allergies may also be allergic to chitosanproducts.

Interactions with warfarin: There is one case report(supported by some laboratory studies) of a patient takingwarfarin whose INR significantly increased after self-medication with 1200mg twice per day of chitosan.Higher INR levels suggest that the patient is at risk forbleeding. Therefore, talk to your doctor, pharmacist orother healthcare providers before taking chitosan togetherwith warfarin.

Coenzyme Q10 (Ubiquinone)

Purpose/Use: CoenzymeQ10 is involved in manydifferent chemical reactionsin the body. It has a chemicalstructure similar to vitamin Kthat is known to counteractthe effects of anticoagulantslike warfarin. It is considered to be a powerful antioxidant.There is some evidence that it may be beneficial for thosediagnosed with cardiovascular diseases (i.e., congestive heartfailure). Side effects are rare and mainly confined tostomach upset, nausea and rash.

Interactions with warfarin: In our review of theliterature, we have discovered conflicting findings on theeffect of coenzyme Q10 on blood clotting response. Therehave been a number of case reports of possible interactionsbetween warfarin and coenzyme Q10. In several cases,ingestion of coenzyme Q10 has been associated withdecreased INR values. A drop in INR value means thatcoenzyme Q10 decreases the effect of warfarin and couldlead to blood-clotting problems. Two animal studies reportthat coenzyme Q10 increases the metabolism of warfarin inthe body, supporting the findings described in the humancases. Other cases reported an increase in INR (and thus anincrease in the risk of side effects such as bleeding) whenpatients took warfarin and coenzyme Q10 together.However, a recent double-blind crossover study in middle-aged patients taking long-term warfarin treatment reportedthat those patients taking coenzyme Q10 experienced nodecrease in INR values compared with those taking aninactive treatment (placebo). Given these conflictingfindings, it is recommended that you be cautious takingcoenzyme Q10 and warfarin at the same time. You shouldalways talk to your doctor, pharmacist or other healthcareproviders before taking coenzyme Q10.

10 11 12

Curbicin

Purpose/Use: Curbicin is a traditional herbal formulafrom Sweden reportedly used for urination difficulties andbenign prostatic hypertrophy. The active ingredients ofcurbicin are extracts from saw palmetto (Serenoa repens),pumpkin seeds (Curcubita pepo) and dwarf palm plants(Sabal serrulata). Curbicin also contains vitamin E. We arenot aware of any reported side effects.

Interactions with warfarin: We are aware of at leasttwo published cases of patients developing an increase inINR while taking curbicin and warfarin. In warfarintreatment, an increase in INR means that curbicin couldpotentiate the effects of warfarin and bleeding problemscould occur. Therefore, be cautious about taking curbicinwhile you are taking warfarin. Talk to your doctor,pharmacist or other healthcare providers before takingcurbicin with warfarin.

Danshen (Salvia miltiorrhiza)

Purpose/Use: Danshen is a Chinese herbal product reportedly used for a range of medical complaints,especially heart problems, such as angina and heart attacks. Side effects of danshen caninclude nausea, stomach pain, and diarrhea.

Interactions with warfarin:Danshen has been reportedto increase the effectiveness ofwarfarin on blood clotting. Therehave been at least two reports ofpatients on warfarin that developed asignificantly increased INR (>8 in onecase) when they started taking danshen. In warfarintreatment, an increase in INR means that danshen couldpotentiate the effects of warfarin and bleeding problemscould occur. Several laboratory studies also showed that thisherbal product raises the level of warfarin in the body, or haseffects that could increase the impact of warfarin, leading tobleeding. Do not take danshen while you are taking warfarin.

Dong Quai (Angelica sinensis)

Purpose/Use: Dong quai is a Chineseherbal supplement reportedly used formenstrual cramps, irregular menstrualperiods, and menopausal symptoms. It contains a natural type of coumarinthat may work like warfarin toprevent blood clots. Side effects of dong quai may include nausea,constipation and diarrhea.

Interactions with warfarin:There have been at least tworeports of patients whoseINR/PT increased whiletaking dong quai andwarfarin. In one case, a patientstabilized on warfarin experienced a doubled INR aftertaking dong quai for four weeks. In another case, a patientpreviously stable on warfarin experienced widespreadbruising and her INR increased to 10 after taking dong quaifor a month. Given these findings, do not take dong quaiwhile taking warfarin.

13 14 15

16 17 18

Evening Primrose Oil (Oenothera biennis)

Purpose/Use: The main activeingredient in evening primroseoil is an omega-6 fatty acidcalled gamma-linolenic acid(GLA). It has been used totreat atopic dermatitis and for anumber of medical conditionsincluding rheumatoid arthritis,premenstrual syndrome anddiabetes. It appears generallysafe at recommended doses, butpatients diagnosed with seizuredisorders or taking a class of drugscalled neuroleptics (e.g., chorpormazine,thioridazine) should use this productwith caution.

Interactions with warfarin: Laboratory studies havereported that the GLA in evening primrose oil mayincrease bleeding times in animals which means it mayincrease the effects of drugs like warfarin. It is not clear ifthere will be a clinically significant interaction. Untilmore research is available, you should be cautious abouttaking evening primrose oil and warfarin. Talk to yourdoctor, pharmacist or other healthcare providers beforeyou take evening primrose oil.

19 20 21

Ginkgo (Ginkgo biloba)

Purpose/Use: Ginkgo isclaimed to improve bloodflow to the brain and bloodvessels in the legs, improvethinking, and the memory. It is reported to be relatively safewhen not mixed with medications.The most common unwanted sideeffects are mild stomach upset, diarrhea,restlessness and headache.

Interactions with warfarin: There has been at least onereport of a patient having increased bleeding while taking aginkgo product with warfarin. In addition, there have been atleast four reported cases of bleeding problems in patientswho were taking ginkgo alone. However, a recent double-blind crossover study in middle aged patients on stable long-term warfarin treatment reported that those patients takingginkgo experienced no increase in INR values or majorbleeding compared with those taking an inactive treatment(placebo). This lack of significant interaction is supported bythree other studies in healthy adults. Animal and laboratorystudies have also reported conflicting findings. Overall, itseems unlikely that there will be a clinically significantinteraction between warfarin and ginkgo at regular doses;however, given the conflicting evidence, it is best to becautious about taking ginkgo if you are taking warfarin. Talk to your doctor, pharmacist or other healthcareproviders before taking ginkgo.

22 23 24

Ginseng, Canadian/American (Panax quinquefolius)

Purpose/Use: Canadian or Americanginseng has reported uses similar to thosefor Asian ginseng. There issome evidence that it has fewer adverse effects, but that it might lower bloodglucose levels.

Interactions with warfarin: One randomized, double-blind, placebo-control in healthy patients reports thatCanadian/American ginseng decreases the anticoagulant effects of warfarin. A decrease in the INR/PT may lead toblood-clotting problems. You should be cautious about usingCanadian/American ginseng if you are taking warfarin. Talk to your doctor, pharmacist or other healthcareproviders before you start taking Canadian/Americanginseng.

Ginseng, Siberian (Eleutherococcus senticosus)

Purpose/Use: Siberian ginseng isreportedly used to increase the body'sresistance to stress, strengthen thebody's immune response, andincrease vitality. Reported sideeffects of Siberian ginseng are rare but include increased bloodpressure, increase in heart rate,insomnia, irritability, and allergicreactions.

Interactions with warfarin: In ourliterature search, we did not find anypublished case reports describing aninteraction between Siberian ginseng andwarfarin. However, it is claimed (based on laboratorystudies) that it can lead to bleeding problems, similar to theway aspirin does. For this reason you should be cautiousabout taking Siberian ginseng with warfarin. Talk to yourdoctor, pharmacist or other healthcare providers before youtake siberian ginseng with warfarin.

Glucosamine/Chondroitin

Purpose/Use: Glucosamine and chondroitin are used fortreating the symptoms of osteoarthritis. Glucosamine isfound in human tissue, including the cartilage in thejoints. Studies have reported that glucosamine andchondroitin may improve the structure of the cartilage andmay have an anti-inflammatory effect. The side effects ofglucosamine and chondroitin are rare and include nausea,diarrhea and stomach pain.

Interactions with warfarin: Health Canada has issued a report that describes patients that experienced anincrease in INR when taking glucosamine with warfarin.In addition there are several case reports that suggesttaking glucosamine/chondroitin combination products canincrease a patient’s INR. An increased INR means thatglucosamine and chondroitin may be enhancing the effectsof warfarin and there is a risk of bleeding. Be cautiouswhile taking glucosamine or chondroitin with warfarin.Talk to your doctor, pharmacist or other healthcareproviders before you start taking glucosamine orchondroitin.

25 26 27

Mango (Mangifera indica)

Purpose/Use: Mango fruit is native to southern Asia andis commonly consumed for its sweet flavour, fiber, andhigh vitamin A and C content. Historical and anecdotalreports suggest that mango fruit may help fight viral andparasitic infections, coughs, and act as a laxative. Sideeffects of mango include allergic contact dermatitis similarto poison ivy and very rarely anaphylactic allergicreactions.

Interactions with warfarin: We are aware of a report ofthirteen male patients stabilized on anticoagulant therapywho experienced increased INR values after ingestingmango fruit and warfarin together (1-6 mangos daily, for 2 days to 1 month before the anticoagulation clinicappointment). An increase in INR after mango intakesuggests you could have bleeding problems if you takemango and warfarin together. Therefore, be cautious abouttaking mango while you are taking warfarin. Talk to yourdoctor, pharmacist or other healthcare providers beforeeating/ingesting mango with warfarin.

Methyl Salicylate (Oil of wintergreen)

Purpose/Use: Methyl salicylate is a volatile oil found ina variety of plants that reportedly attracts pollinating beesand protects the plants from pests. Oil of wintergreencontains 98% methyl salicylate and is a common source of this volatile oil. It is the active ingredient in many over-the-counter analgesic topical preparations used formusculoskeletal pains and aches. Side effects includeallergic contact dermatitis and rarely anaphylacticreactions.

Interactions with warfarin: We are aware of multiplecase reports of interactions between methyl salicylate andwarfarin. Four of these reported that the patientsdeveloped an elevated INR while using topical methylsalicylate and warfarin. One resulted in a life-threateningbleed. An increase in INR means that methyl salicylatemay potentiate the effect of warfarin, and cause bleedingproblems. Do not use methyl salicylate while you aretaking warfarin.

28 29 30

Milk Thistle (Silybum marianum)

Purpose/Use: Milk thistle has along history of traditional usesfor many different types ofliver disorders. Although,more research is needed toascertain whether it is usefulclinically, the availablestudies suggest that it isgenerally safe. It is possible tobe allergic to milk thistle (as with any other plant).

Interactions with warfarin: One laboratory study suggests thatcompounds found in milk thistle have the potential toaffect the metabolism of warfarin if the two products aretaken together. It is not clear if this is a clinically-significant interaction. Until more information is available, it is probably best to use caution and talk toyour doctor, pharmacist or other healthcare providersbefore taking milk thistle with warfarin.

Nettle (Urtica dioica)

Purpose/Use: Nettle has beenused medicinally to help managebenign prostatic hyperplasia,urinary tract disorders andarthritis among other things. Itis likely safe when used innormally recommended medicinaldoses, but should not be used bywomen who are pregnant, as it hasbeen reported to cause contractions ofthe uterus in animals.

Interactions with warfarin: Nettle rootcontains a compound (coumarin) that isknown to increase the effects ofanticoagulants such as warfarin. Nettle leaves also containa compound (vitamin K) that can in high doses impact theactivity of warfarin. A laboratory study reported that nettlehas the potential to interact with a number of medicationsincluding drugs like warfarin. It is not clear if this is a clinically-significant interaction.Until more information is available, it is probably best touse caution and talk to your doctor, pharmacist or otherhealthcare providers before taking nettle with warfarin.

Omega 3 Fatty Acids (Fish oils)

Purpose/Use: Omega 3 fatty acids, most commonlyfound in fish oil, include alpha-linolenic acid,docosahexaenoic acid, and eicosapentaenoic acid. There isgrowing literature suggesting that they may be beneficialfor a wide range of cardiovascular conditions and arthritis.Allergic reactions are possible to supplements containingomega 3 fatty acids, and mild, transient gastrointestinalupset are the most commonly reported adverse effects.

Interactions with warfarin: There are a number of casereports in which patients taking warfarin and omega 3fatty acids together have experienced increased INRs orbleeding. Diets high in fatty fish content have also beenreported to be associated with prolonged bleeding times.The research is conflicting with some studies reporting the potential for an interaction with drugs like warfarinand others concluding such an interaction is unlikely. Until more information is available, it is probably best touse caution and talk to your doctor, pharmacist or otherhealthcare providers before taking omega 3 fatty acidswith warfarin.

31 32 33

Quercitin

Purpose/Use: Quercitin is a flavonol found in manydifferent kinds of plants. It has been used as a medicinalproduct in the management of many conditions includingthose of cardiovascular origin. However, there are not a lotof good studies about its effectiveness. It is generallyconsidered safe at doses consistent with normal dietaryintake. Higher doses have been associated with a range ofside effects including nausea, vomiting, and headaches.

Interactions with warfarin: A laboratory studysuggests that quercitin may decrease the blood’s ability toclot and thus possibly increase the effects of warfarin. It isnot clear if this is a clinically significant interaction. Untilmore information is available, it is probably best to usecaution and talk to your doctor, pharmacist or otherhealthcare providers before taking quercitin with warfarin.

Quilinggao

Purpose/Use: Quilinggao is a Chinese herbal productfrom the “essence of a tortoise shell” reportedly used forenhancing skin complexion, reducing “internal heat”, andimproving general health. The combination of herbs inquilinggao varies between different brands but oftenincludes the following herbs which may have anti-plateletactivity: Chuanbeimu (Fritillaria cirrhosa), Beimu(Fritillaria spp.), Chishao (Paeoniae rubra, Chinesepeony), Jinyinhua (Lonicera japonica), and Jishi (Poncirustrifoliata). We are not aware of any published reports onthe side effects of quilinggao.

Interactions with warfarin: We are aware of at leastone case report of a patient on stable warfarin therapy whoconsumed quilinggao and developed an increase in INRand experienced bleeding from the gums and nose as wellas skin bruising. An increase in INR while taking warfarinmeans that quilinggao may potentiate the effect ofwarfarin and bleeding problems could occur. Do not usequilinggao with warfarin.

Red Clover (Trifolium pratense)

Purpose/Use: Red clover containsphytoestrogens and is commonlyused in an attempt to treatsymptoms associated withmenopause like hot flashes. It is alsosometimes used for high cholesteroland osteoporosis. It is likely safein the usual recommendedmedicinal doses, but shouldbe used with caution by childrenand anyone not able to takeestrogen products.

Interactions with warfarin:Red clover contains multiplecompounds that have been reported in laboratory studiesto decrease platelet aggregation and thus theoretically mayincrease the effects of drugs like warfarin which do thesame thing. There is one case report of a woman taking acombination herbal product that contained red clover,dong quai and siberian ginseng who experienced bleedingin her brain. It is not clear if the herbal product was thecause of the bleeding. However, until more information isavailable, it is best to use caution and talk to your doctor,pharmacist or other healthcare providers before taking redclover with warfarin.

34 35 36

Royal Jelly

Purpose/Use: Royal jelly is the nutrient-rich substancethat worker honey bees produce to feed to their queen bee.It has been purported to be useful to enhance energy,stamina and longevity; however, scientific evidence tosupport these claims are lacking. It should be avoided byanyone allergic to bees or bee products.

Interactions with warfarin: There is one case report ofa gentleman previously stabilized on warfarin whose INRincreased significantly when he began taking royal jellyfor 1 week. Until further research is available, it is best touse caution and talk to your doctor, pharmacist or otherhealthcare providers before taking royal jelly withwarfarin.

Saw Palmetto(Serenoa repens)

Purpose/Use: Saw palmetto istaken to help men with symptomsof prostate enlargement. Sideeffects of saw palmetto aregenerally rare and mild, butinclude nausea or upsetstomach, headache, anddiarrhea.

Interactions withwarfarin: We are notaware of any reports ofinteractions between sawpalmetto and warfarin.However, there is one report of a patient who experienced prolonged bleeding duringsurgery while taking saw palmetto. Although the PT andPTT values during and after surgery in this patient werenormal, the increased bleeding time is a cause for concern.Animal studies have shown that saw palmetto can causebleeding by a mechanism similar to aspirin. Be cautiousabout taking saw palmetto with warfarin. Talk to yourdoctor, pharmacist or other healthcare providers beforetaking saw palmetto and warfarin together.

Soy (Glycine soja, Glycine max)

Purpose/Use: Soy products areclaimed to promote cardiovascularhealth, treat menopausal symptoms,and prevent breast cancer. Sideeffects of soy are rare but includeconstipation, bloating, nausea, andallergic skin rash. It has beenreported to trigger asthma andhypothyroidism in susceptibleindividuals.

Interactions with warfarin: We are aware of at least one recent case report of apatient taking 240 ml soymilk daily for four weeks while onwarfarin therapy whose INR decreased. In patients takingwarfarin, a decrease in INR means that warfarin is notworking as effectively and that blood clots could develop.Therefore, be cautious about consuming soy while you aretaking warfarin. Talk to your doctor, pharmacist or otherhealthcare providers before taking soy and warfarintogether.

37 38 39

St. John's Wort (Hypericum perforatum)

Purpose/Use: St. John’s Wort isused for the management of mildto moderate depression. Sideeffects of St. John's Wort occur in1-3% of people and can include drymouth, dizziness, confusion, fatigue,and skin rash, especially with sunexposure.

Interactions with warfarin: We are aware of a report ofnine patients who developed a decrease in their INR whenthey started taking St. John's Wort. Although none of thepatients developed clotting problems, the decline in INR wasthought to be significant. The finding that St. John’s Wortincreases the metabolism of warfarin is supported by an un-blinded clinical trial in healthy patients. However, there aretwo additional case reports that found that taking St John’sWort and warfarin together led to an increased INR. It isimportant to note that the St. John’s Wort products taken bythese patients were not tested for purity and thus may havecontained contaminants responsible for this unusual reaction.In patients taking warfarin, a decrease in INR meanswarfarin is not working effectively and that blood clots coulddevelop. Recently, the United Kingdom's Committee onSafety on Medicine warned that St. John's Wort should notbe used with warfarin. Talk to your doctor, pharmacist orother healthcare providersb efore taking these productstogether. You may need to have your INR/PT blood testperformed more frequently, or you may be counseled not totake them together.

Tea - Black or Green (Camellia sinensis)

Purpose/Use: Black teais a common sourceof caffeine and thuscan have stimulanteffects as well as havemedicinal effects on theheart and kidney (e.g., it increasesurination). Green tea is reportedlyused for chronic gastritis,cardiovascular disease (e.g.,atherosclerosis), liver disease, cancerprevention and weight loss. Side effectsof both appear to be rare and includeallergy and gastrointestinal upset.

Interactions with warfarin: We are aware of one casereport each of patients who may have experiencedinteractions between black or green tea and warfarin. Onepatient experienced an increase in her INR when shestopped drinking black tea, meaning that she was at riskfor side effects from the warfarin. Another patientdeveloped decreased INR values after taking warfarintogether with one and a half gallons of green tea each dayfor one week prior to his INR test. While taking warfarin,a decrease in INR means that warfarin may not beworking properly and you may experience blood-clottingproblems. Therefore, be cautious while taking green teawith warfarin. Talk to your doctor, pharmacist or otherhealthcare providers before taking black or green tea withwarfarin.

Vitamin K

Purpose/Use: Vitamin K is an essential co-factor forseveral compounds that are part of the coagulation processin the human body. It is found in many dietary sourcessuch as green leafy vegetables and fruits.

Interactions with warfarin: Increased intake of vitaminK has been shown to decrease the effect of warfarin inpatients. Therefore, be cautious with your vitamin Kintake from dietary and other sources while you are takingwarfarin. Talk to your doctor, pharmacist or otherhealthcare providers if you have any questions.

40 41 42

Wolf Berry or Goji Berry (Lycium barbarum)

Purpose/Use: Wolf berry is a Chinese herbal supplementreportedly used for the treatment of back and leg aches,impotence, visual problems, and vertigo. We are not awareof any reported side effects for this herb.

Interactions with warfarin: We are aware of a casereport of a patient previously stabilized on warfarin takingwolf berry tea who developed an elevated INR. In patientstaking warfarin, an increase in INR means that itsanticoagulant effect is potentiated and bleeding problemscould occur. Therefore, be cautious about taking wolfberry and warfarin together. Talk to your doctor,pharmacist or other healthcare providers before takingwolf berry or goji berry together with warfarin.

SummaryIt is clear that more research studies need to beconducted to learn if herbal products are effective andif they are safe to take with warfarin and othermedications. Tell your doctor and other healthcareproviders the names and amounts of any herbalproducts you are taking. You should always talk toyour doctor, pharmacist or other healthcare providersbefore you start taking any herbal products -especially if you are taking warfarin.

If you take herbal products with warfarin you mayneed to have your INR/PT checked more frequently tobe sure your warfarin is working well. You may alsoneed to have your dose of warfarin increased ordecreased.

If you notice any of the following problems, call yourdoctor:

• nose bleeds• bleeding gums• easy bruising• bleeding that does not stop after a cut• heavy or prolonged menstrual period• red or dark brown urine• coughing up blood• chest pain• headache, dizziness and/or weakness• swelling in arms or legs

The authors of this booklet do not claim to have reviewed all the literatureand believe there is additional literature that may not have come to ourattention. Further, the authors make no judgments as to the truthfulnessof the literature or the accuracy of any claims. The Purpose/Use foreach herbal product is based on unsubstantiated claims in literature aswell as historical claims, the truthfulness of which has not been subject torigorous review by the Natural Health Products Directorate (HealthCanada). Such claims are included in this booklet only as a background totheir possible interaction with warfarin.

Notes:

43 44 45

Notes:

Developed by thePhiladelphia College of Pharmacyat the University of the Sciences

in Philadelphia

Revised 2012 by:Heather Boon, BSc.Phm., Ph.D.,

Associate Professor, Leslie DanFaculty of Pharmacy,University of Toronto

Taro Pharmaceuticals Inc.130 East Drive, Brampton

Ontario L6T 1C11-800-268-1975

www.taro.ca

© 2000 Taro Pharmaceuticals Inc.Revised (2012)

PrTaro-Warfarin

Over 50 yearsof warfarin experience

For more information, Please call 1-800-268-1975

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