Penbutolol (sulfate) (Standard) is the analytical standard of Penbutolol (sulfate). This product is intended for research and analytical applications. Penbutolol sulfate ((-)-Terbuclomine) is a potent beta-adrenoceptor and 5-HT receptor antagonist with Ki of 11.6 nM and 11.9 nM for 5-HT in rat cornu ammonis 1 (CA1) and human CA3[1][2].