From experience, when dealing with the consumption of anti-anxiety medication and grapefruit/kava within short periods of time, there really are no severe risks involved if you happen to do this every so often. A couple times I have taken Xanax, grapefruit juice, and kava all within the same day (spread out through the day) and I was absolutely fine. The key is moderation here just like most other things. When dealing with a mix of grapefruit juice or alike inhibitors (kava) with prescription medication, I'd be greatly more concerned with mixing with much more lethal drugs such as pain medications and those of which you are more easily to overdose on--even alcohol. From doing some research, the lethal overdose for Buspar ranges around 375mg/day and Xanax 975 times the maximum recommended daily human dose of 10mg/day. So as you can see, you would have to take ginormous amounts of the drug along with enormous amounts of kava before you would enter into the danger zone and even then you would pass out before you were able to accomplish such a thing. Of course, this isn't to say it wouldn't put a good deal of stress on the liver because it surely will, but so will a good night of drinking alcohol.