Velserine is an uncommon slow-acting poison that causes neural instability. Its effects include seizures and paralysis. The effects last several hours. Low amounts of Velserine are typically used by criminals as a stunning agent in crimes where the assailants want to render their victims immobile (and unable to form memories) without killing them; the chances of death are rare in these case. Larger amounts will cause prolonged periods of seizures.
Many Nepleslian and NH-22C Yamataian have white blood cells that will actually detect and destroy the toxin over time. Pure humans, however, may take several days to fully get it out of their systems.