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Kudzu Extract Treatment Does Not Increase the Intoxicating Effects of Acute Alcohol in Human Volunteers


Reprint requests: David M. Penetar, PhD, McLean Hospital/Harvard Medical School, 115 Mill Street, Belmont, Massachusetts 02478; Tel.: +1 617 855 2913; Fax: +1 617 855 3711; E-mail:


Background:  Isoflavone administration in the form of a purified extract from the herbal medication kudzu root has been shown to reduce, but not eliminate, alcohol consumption in alcohol-abusing and alcohol-dependent men. The precise mechanism of this action is unknown, but 1 possible explanation for these results is that the isoflavones in kudzu might actually increase the intensity or duration of alcohol’s effects and thus delay the desire for subsequent drinks. This study was designed to test this hypothesis.

Methods:  Twelve (12) healthy adult men and women (27.5 ± 1.89 years old) who consumed moderate amounts of alcohol (7.8 ± 0.63 drinks/wk) participated in a double-blinded, placebo-controlled crossover study in which they were treated with either kudzu extract (total isoflavone dose of 750 mg/d) or matched placebo for 9 days. On days 8 and 9, participants received an acute challenge of ethyl alcohol (either 0.35 or 0.7 g/kg alcohol). During the challenges, the following measures were collected: subjective effects, psychomotor (body sway), cognitive performance (vigilance/reaction time), physiological measures (heart rate and skin temperature), and plasma ethanol concentration.

Results:  Alcohol resulted in a dose-related alteration in subjective measures of intoxication, impairment of stance stability, and vigilance/reaction time. Kudzu extract did not alter participants’ subjective responses to the alcohol challenge or to alcohol’s effects on stance stability or vigilance/reaction time. However, individuals treated with kudzu extract experienced a slightly more rapid rise in plasma ethanol levels, but only after the 0.7 g/kg dose. This transient effect during the first 30 minutes of the ascending plasma alcohol curve lasted only 10–15 minutes; there were no differences in peak plasma alcohol levels or alcohol elimination kinetics. Additionally, kudzu pretreatment enhanced the effects of the 0.7 g/kg dose of alcohol on heart rate and skin temperature.

Conclusions:  These data suggest that individuals who drink alcohol while being treated with kudzu extract experience no adverse consequences, and furthermore the reported reductions in alcohol intake after kudzu extract treatment are not related to an alteration in alcohol’s subjective or psychomotor effects.