Herbal medicines: anticoagulation effects


Garlic is used for its potential to prevent atherosclerosis by reducing blood pressure, thrombus formation, and serum lipid and cholesterol levels. The development of concentrated garlic preparations has made it possible for patients to take otherwise unachievable high doses, which may increase the risk of adverse effects.

The pharmacologic effects of garlic are primarily attributed to organosulfur compounds. Several of these compounds inhibit platelet aggregation in a dose-dependent manner. The inhibition of platelet aggregation appears to be irreversible and may potentiate the effect of other compounds such as prostacyclin and indomethecin. The mechanism by which these effects occur is unknown, although some studies have implicated the cyclooxygenase pathway and direct interaction with the platelet fibrinogen receptor.

The potential for irreversible inhibition of platelet function warrants the discontinuation of garlic at least 7 days before surgery, especially if intraoperative or postoperative bleeding is a concern or other platelet inhibitors are used.

Ginkgo is used by patients with cognitive disorders, peripheral vascular disease, age-related macular degeneration, vertigo, tinnitus, erectile dysfunction, and altitude sickness. The compounds believed to be responsible for ginkgo’s pharmacologic effects are the terpenoids and flavonoids. These compounds alter vasoregulation, act as antioxidants, modulate neurotransmitter and receptor activity, and inhibit platelet-activating factor.

Based on the pharmacokinetic data and the risk of bleeding, ginkgo should be discontinued at least 36 hours before surgery.

Ginseng has been used for virtually every purpose, including to promote health, immune function, endocrine function, athletic performance, and cognitive function and to treat cardiovascular disease, diabetes mellitus, cancer, impotence, and viral infections.

Most pharmacologic effects of ginseng are attributed to the ginsensosides, a group of compounds that act as steroid hormones. It is not known, however, whether long-term use of ginseng can cause the well-described complications of long-term steroid use.

Ginsenosides inhibit platelet aggregation in vitro and prolong the PT and PTT in animal studies. They also lower postprandial blood glucose in patients with type 2 diabetes mellitus. Although it has great therapeutic potential, it can also create unintended hypoglycemia. (patients fasting preoperatively)

The pharmacokinetics of ginsenosides suggest that patients should discontinue ginseng use at least 24 hours before surgery, but discontinuation at least 7 days before surgery is preferred because of the potential for irreversible platelet inhibition.

Saw Palmetto is used to treat symptoms associated with BPH.

The pharmacologic activity of saw palmetto has not been attributed to a single compound. Multiple mechanisms of action have been proposed to explain its therapeutic effects: inhibition of estrogen receptors, blocking prolactin receptor signal transduction, interference with fibroblast proliferation, induction of apoptosis, inhibition of α1-adrenergic receptors, and anti-inflammatory effects. Saw Palmetto has been associated with excessive intraoperative bleeding. This is attributed to saw palmetto’s anti-inflammatory effects, specifically the inhibition of cyclooxygenase and subsequent platelet dysfunction.

Because there are no pharmacokinetic data for saw palmetto, specific recommendations for preoperative discontinuation cannot be made.

Herbal Medicines

  • Garlic: inhibits platelet aggregation (organosulfur), discontinue for seven days
  • Ginkgo: inhibits platelet activating factor (terpenoids, flavonoids), discontinue for thirty six hours
  • Ginseng: inhibits platelet aggregation and lowers blood glucose (ginsensosides [mimic steroids]). Check PT/PTT/glucose, d/c for 24 hours (preferably seven days)
  • Saw Palmetto: associated with excessive intraoperative bleeding (mechanism unknown, likely multiple), in the absence of pharmacokinetic data, no recommendations re: preoperative continuation can be made

Herbal medicines that increase the risk of bleeding:

  • Black Cohosh: Claims to be useful for menopausal symptoms. Contains small amounts of anti-inflammatory compounds, including salicylic acid. Theoretically could have intrinsic/additive antiplatelet activity.
  • Chamomile: Claims to reduce inflammation and fever, to be a mild sedative, relieve stomach cramps. Increases risk of bleeding because it contains phytocoumarins, which have additive effects with warfarin.
  • Feverfew: Claims to prevent migraines. Increases the risk of bleeding because it individually inhibits platelet aggregation, has additive effects with other antiplatelet drugs. Also additive effects with warfarin.
  • Fish Oil: Claims to prevent/treat atherosclerotic CV disease (800-1500mg/day). Also used to decrease triglycerides (>4g/day). Dose dependent bleeding risk increases with dose >3g/day.
  • Garlic, Ginger, Ginko, Ginseng: Increases bleeding risk by interacting with antiplatelet drugs to inhibit platelet aggregation and inhibit fibrinolysis. Also augments warfarin.

Herbal medicines that increase clotting risk:

  • Coenzyme Q10: Claims to enhance insulin sensitivity in diabetics, and as an antioxidant to act as an anticancer medication. Decreases response to warfarin.
  • Goldenseal: Has some antiseptic properties for mouth sores, eye sores, and vaginal infections. Increases risk of thromboembolism by opposing effects of warfarin and heparin.
  • St. John’s Wort: For use as an MAOI, for patients with mild to mod depression. Increases thromboembolism risk by reducing blood levels of warfarin.

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