Kendal, when Sandra wrote the book in 1999 very small testing was going on and if you read the following press release you might miss the point that it is for male dogs which maybe is what Sandra did. I did it myself - I missed that it has only been approved for males. I have met her a couple of times at dog shows in Tucson but I have never spoken to her about this. You can also read a great deal about this if you google Neutersol.
http://atmizzou.missouri.edu/jul03/Neutering.htm