Pharmacodynamic interaction study of Allium sativum   (garlic) with cilostazol in patients with type II diabetes mellitus

Aim: Garlic is available as an over-the-counter herbal supplement and is known to have antiplatelet properties. Because of scarcity of clinical data regarding the safety of concomitant use of garlic supplements and anticoagulants, we tried to evaluate the effects of coadministration of single and multiple doses of garlic and cilostazol on platelet aggregation.
Materials and Methods: The study was a randomized, open label, placebo-controlled, crossover study of type II diabetic patients, where 14 patients were enrolled and 10 completed the study. The patients were administered 600 mg aged garlic extract, 100 mg cilostazol, 600 mg aged garlic extract, and cilostazol or placebo for seven days as per prior randomization schedule. Blood samples for platelet aggregation and bleeding time and clotting time were collected before and 2, 4, and 6 hours after single-dose drug administration and after seven days of treatment.
Results: After single- and multiple-dose administration of garlic, there was a significant inhibition of platelet aggregation at 2 hours, whereas with cilostazol, the inhibition was significant at all the three time points tested, with 4 hours showing maximum inhibition. Coadministration of garlic and cilostazol in single and multiple doses for seven days did not produce any significant change in the antiplatelet activity of the individual drugs.
Conclusions: Coadministration of aged garlic extract and cilostazol did not enhance the antiplatelet activity compared with individual drugs. Large randomized trials are needed to further evaluate the possible interaction of garlic in higher doses and in combination with other antiplatelet activity drugs.