People's Pharmacy

Coumadin

Generic Name:warfarin

Revised:4/1/2000

Table of Contents

Side Effects and Interactions

Side effects of Coumadin therapy are uncommon if the dose is appropriate and the blood is carefully monitored.

Some people have occasionally reported hair loss, skin rash, itching, nausea, fever, digestive upset, diarrhea, hepatitis, purple toes, red-orange urine, prolonged, painful erections, and mouth ulcers.

Report any symptoms to your physician promptly.

A large number of over-the-counter and prescription medications may interact with Coumadin in a dangerous way.

Some drugs, including barbiturates and the anticonvulsant Tegretol (carbamazepine), can reduce the effectiveness of Coumadin and increase the risk of blood clots.

Others, such as the antibiotics metronidazole (Flagyl) or co-trimoxazole (Bactrim, Septra, etc.), can increase the blood thinning potential of Coumadin and thereby raise the risk of dangerous bleeding.

The drugs Nolvadex (tamoxifen) and Danocrine (danazol) can also increase susceptibility to hemorrhage when a woman is taking Coumadin.

Because aspirin also acts as an anticoagulant, though it works differently from Coumadin, it should be avoided unless your doctor specifically prescribes it and monitors bleeding time.

The heart drug Cordarone (amiodarone), the ulcer drug Tagamet (cimetidine), anabolic steroids such as Anadrol-50 (oxymetholone) and antibiotics such as Biaxin (clarithromycin), erythromycin or tetracycline can also make bleeding more hazardous for people on Coumadin.

Some individuals may also be vulnerable to increased bleeding when they take the new antidepressants Paxil (paroxetine), Prozac (fluoxetine) or Zoloft (sertraline).

Also beware of quinine derivatives such as heart medicines or over-the-counter leg cramp medicines.

Patients should be wary of taking thyroid drugs, cholesterol medications and tuberculosis medicines in combination with Coumadin. Vitamins E and K could also be problematic.

Anticoagulants such as Coumadin may pose a hazard when taken with the herb ginkgo biloba. An elderly woman on Coumadin had a hemorrhagic stroke after two months of ginkgo.

If the extract of the herb hawthorn is taken together with Coumadin, careful monitoring of bleeding time (through PT and INR) is essential.

The anticlotting action of the herb horse chestnut (aesculin) may interact with Coumadin to increase the risk of bleeding. This combination should be avoided.

It is possible that juniper berries may interact with Coumadin to increase the risk of bleeding. This possibility remains hypothetical.

Licorice binds to serum albumin and may interact with Coumadin. The coumarins in licorice may also potentiate the action of Coumadin, possibly leading to unexpected bleeding.

Despite research suggesting that ginseng might reduce platelet aggregation, the only reported interaction with Coumadin resulted in a decreased INR (a measure of blood's propensity to clot).
This suggests that ginseng may counteract Coumadin's benefit.

A red clover extract containing coumarin derivatives might in theory interact with the anticoagulant Coumadin. Close monitoring of prothrombin time or INR is advisable.

Psyllium can affect the absorption of Coumadin. To avoid this, psyllium should be taken at least an hour after Coumadin.

In theory garlic could increase the risk of bleeding in people taking anticoagulants such as Coumadin.

The herb pau d?arco causes vitamin K-reversible bleeding, strongly suggesting that it would interact with Coumadin to increase the danger of hemorrhage.

If the herb arnica were to be taken internally, in addition to serious side effects, it would possibly interact with Coumadin because of the herb's ability to inhibit platelet aggregation.

The anticoagulant activity of astragalus may interact with that of Coumadin, increasing the risk of bleeding.

This herb capsicum (cayenne) may have the potential to prolong clotting time, so people taking Coumadin should exercise caution before eating quantities of chili peppers.

Cayenne also inhibits liver enzymes (CYP1A2) and thus slows the metabolism of Coumadin.

In theory the coumarins in the herb chamomile might potentiate Coumadin's effect. Careful monitoring of bleeding time (through PT and INR) are recommended if chamomile is to be used together with Coumadin.

Also in theory, the herb feverfew could increase the risk of bleeding in people taking Coumadin.

Because ginger inhibits prostaglandin synthesis and reduces platelet aggregation, caution should be exercised in combining it with Coumadin. The combination could result in unexpected bleeding.

It is not known whether the coumarins in the herb dong quai might interact with Coumadin. To be safe, any woman taking both dong quai and Coumadin should discuss this situation with her doctor and should have bleeding time (PT and INR) checked frequently, especially when starting or stopping the herb.

Goldenseal reportedly limits the effectiveness of the Coumadin.

As a general rule, do not take any other medication or herbs without first checking with your physician and pharmacist.