Attenuation of the Effect of 100 mg Aspirin on Platelet Aggregation in Regular Kava Drinkers

Background and Purpose: Numerous interactions between herbal medicines and conventional drugs have been documented. While the significance of many interactions is uncertain, several others may have serious clinical consequences. Kava (Piper methysticum) is an ancient crop of the western Pacific. Kava preparation and extracts are very popular in the Pacific and the potential remains for herbal supplements like kava to interact negatively with other drugs like aspirin in vivo which needs to be thoroughly explored. Management of cardiovascular disease in Fiji includes anti-platelet drugs, especially aspirin which is prescribed routinely.

Aim: Our study aimed to assess the effect of two different doses of aspirin (100 mg and 300 mg) on the degree of platelet aggregation induced by collagen amongst healthy non kava drinkers and kava drinkers. The objective of this study was to examine potential effect of concomitant aspirin on platelet aggregation (PA) in kava drinkers.

Methods: Platelet aggregation was measured using whole blood platelet aggregometer (Chronology Corp) using collagen as an aggregating agent in two main ethnic groups, Fijians and Indo-Fijians, before and after the intake of a single dose of 100 mg and 300 mg of aspirin. The Fijian and Indo-Fijian volunteers were divided into three groups, non-kava drinkers (NKD), occasional-kava drinkers (OKD) and regular-kava drinkers (RKD).

Results: The results were found to be non-significant in NKD, OKD and RKD Fijians and Indo-Fijians before aspirin intervention, the intake of kava did not have any effect on platelet aggregation. Overall PA remained within the normal range (15-27 Ω). After a single dose of 100 mg of aspirin, a large number of participants in both ethnic groups of RKD were found to have decreased aspirin sensitivity. The decreased aspirin sensitive participants had their PA within the normal range (15-27 Ω) even after administration of aspirin. All the participants showed a reduction in PA (<15 Ω) after the administration of 300 mg of aspirin. However, the difference was statistically non- significant (p>0.05). The most important finding of this study is that 100 mg aspirin had significantly less inhibitory effect on PA in both Fijian and Indo-Fijian RKD (p < 0.001). Conclusion: Our studies show a reduced effect of aspirin on platelet aggregation in regular kava drinkers (RKD).