The synergy of Yohimbine HCL with caffeine is substantial.
Not sure if you took it with coffee, diet coke or straight out caffeine but when combined it's like the ECA, Ephedrine (Primatine) + Caffeine (dirt cheap tablets 200mg) + Aspirin (82mg), combo- it packs a much bigger punch.
Start with a very low dose (2.5 mg or less) with breakfast but avoid caffeine. As you grow accustomed to it you can add caffeine and/or increase the dose. It is good stuff but it will damn sure let you know if you do too much too fast.