I'd stay away from these 'sex' or 'penis enlargement' pills, everyone of them! You dont know where the ingredients are from, how pure they are or if they really are what the company says they are. Regarding Yohimbe the so called wonder cure for erectile dysfunction, just stay away from it but if you must make sure you know what your letting yourselves in for;
http://en.wikipedia.org/wiki/Yohimbine
http://www.drugs.com/mtm/yohimbine.html
Its also been found to potentiate the effects of certain medications such as Venlafaxine and Fluoxetine
http://www.ncbi.nlm.nih.gov/puBathmateed/17622775
What SICKENS ME is that these companies and even those responsible for running penis enlargement sites fail to see the dangers of this stuff if taken in wrong amounts or by people who are on meds that react with it. One example again with Yohimbe is
Modafinil, take both if you want to increase chances of death as they will work together in increasing your heart rate and blood pressure through the freaking roof!! does the company or sites like [words=http://www.mattersofsize.com/join-now.html]MOS[/words] warn you? NO but I do because I actually do care and dont want anyone to go through what I did nearly a year ago, which was an acute overdose of Caffeine powder that nearly killed me.