because selenium is part of the enzyme glutathione-peroxidase Simplified catalytic mechanism glutathione peroxidase: in the Modeling the Catalytic Cycle of
Description
The manufacturer discontinued both formulations in 2008 for business reasons, and a 2013 Federal Register determination confirmed the withdrawal was not for reasons of safety or effectiveness

Your treatment shouldn't add to that suffering

Research protocol (based on published studies): Dose: Varies by study
Studies show men need 16 mg/day of vitamin B3, while women need 14 mg/day [2]