Nepicastat (SYN117) is a selective, potent, and orally active dopamine-beta-hydroxylase inhibitor capable of crossing the blood-brain barrier (BBB), producing concentration-dependent inhibition of bovine and human dopamine-beta-hydroxylase with IC50s of 8.5 nM and 9 nM [1] [2] [3].

Nepicastat, administered orally at doses ranging from 3 to 100 mg/kg at 12-hour intervals for three consecutive doses, elicited dose-dependent reductions in noradrenaline levels while increasing dopamine levels and the dopamine/noradrenaline ratio in the mesenteric or renal arteries, left ventricle, and cerebral cortex of 15-16 week-old male spontaneously hypertensive rats (SHRs).