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.