Tasosartan is a long-acting angiotensin II (AngII) receptor blocker. Tasosartan is infrequently in the treatment of hypertension and heart failure. The manufacturer withdrew it from FDA review after phase III clinical trials showed elevated transaminases. Tasosartan blocks the renin-angiotensin-aldosterone system (RAAS) at the level of the AT1 receptor that mediates most, if not all, of the important actions of Ang II. Tasosartan binds reversibly to the AT1 receptors in vascular smooth muscle and the adrenal gland. As angiotensin II is a vasoconstrictor, which also stimulates the synthesis and release of aldosterone, blockage of its effects results in decreases in systemic vascular resistance.