4-(2,3-Epoxypropoxy-d5)carbazole is the labeled analogue of 4-(2,3-Epoxypropoxy)carbazole (E589250), an intermediate in the synthesis of Carvedilol (C184625), a nonselective β-adrenergic blocker with α1-blocking activity. Carvedilol is an antihypertensive used in the treatment of congestive heart failure.