Aged Garlic Extract May Be Safe for Patients on Warfarin Therapy

Abstract

Garlic has been known to have antiplatelet properties. Because of the lack of major clinical data regarding the safety of concomitant use of garlic supplements and anticoagulants, we decided to evaluate the safety of using garlic extract along with oral anticoagulation therapy. During this project we tested aged garlic extract (AGE), a commercial garlic preparation, with warfarin (Coumadin). Sixty-six (66) patients were screened for a double-blind, randomized, placebo-controlled pilot study. Fifty-two (52) patients were randomized for the project. Forty-eight patients (30 men and 18 women, with a mean age of 56+/-10 years) completed the study. Eighteen patients (14 before randomization, 4 after randomization) were dropped from the study. The study medication (AGE or placebo) was administered at a dose of 5 mL twice a day for 12 wk. Potential bleeding and thromboembolic episodes were monitored. There was no evidence of increased hemorrhage in either the placebo or the AGE group. Adverse events included headache, fatigue, colds, and dizziness. However, no significant difference was found in the incidence of these minor adverse events between the groups. Thus, the adverse events are unlikely to be attributable to AGE. The results suggest that AGE is relatively safe and poses no serious hemorrhagic risk for closely monitored patients on warfarin oral anticoagulation therapy. Although the risk-benefit ratio of AGE use needs to be considered carefully when warfarin therapy is necessary, its positive effects may be beneficial to people with a high-risk background or who are taking cardiovascular medications.

Garlic (Allium sativum L.): Adverse effects and drug interactions in humans

“…These reports, however, contained inadequate information to assess the likelihood of an interaction. Recently, Macan and colleague [117] have suggested that AGE is relatively safe and poses no serious hemorrhagic risk for closely monitored patients on warfarin therapy.…”

Potential Health Benefits of Garlic (Allium Sativum): A Narrative Review

“…However, a recent double-blinded placebo controlled pilot study by Macan et al (2006) of 48 patients tested admnistration of aged garlic extract with concomitant use of warfarin (Coumadin®) and found no evidence of increased hemorrhage in either the placebo or the garlic users. The authors from UCLA determined that "the results suggest that AGE is relatively safe and poses no serious hemorrhagic risk for closely monitored patients on warfarin oral anticoagulation therapy.…”

Essentials of Herb-Drug Interactions in the Elderly With Cardiovascular Disease

“…47 However, in healthy volunteers, garlic in combination with warfarin was shown to have no effect on INR or bleeding risk over short-term follow-up. 36,44 Garlic should be used with caution in those on oral anticoagulants, as garlicassociated postoperative bleeding 48 55 which was confirmed in a more recent trial (CAMUS) funded by the NCCIH that used up to 960 mg/day of saw palmetto extracts in men with moderate lower urinary tract symptoms. 56 Reported adverse reactions from saw palmetto include sexual dysfunction, fatigue, tachycardia, angina pectoris, extrasystole, 57 hypertension, 58 intraoperative hemorrhage, 59 bleeding susceptibility, 60 pancreatitis 61 and cholestatic hepatitis.…”

“…43 However, other trials have shown no significant effects on total cholesterol, low-density-lipoprotein cholesterol, blood pressure, platelet count or triglycerides in patients taking garlic supplements. 36,44 Garlic is believed to have antithrombotic activity 45 and decrease platelet aggregation, 46 which can increase clotting time and risk of bleeding when taken with anticoagulants such as warfarin. 47 However, in healthy volunteers, garlic in combination with warfarin was shown to have no effect on INR or bleeding risk over short-term follow-up.…”