Pyritinol also called pyridoxine disulfide or pyrithioxine (European drug names Encephabol, Encefabol, Cerbon 6) is a semi-synthetic water-soluble analog of vitamin B₆ (Pyridoxine HCl). It was produced in 1961 by Merck Laboratories by bonding 2 vitamin B₆ compounds (pyridoxine) together with a disulfide bridge. Since the 1970s, it has been a prescription and OTC drug in several countries for cognitive disorders, rheumatoid arthritis, and learning disorders in children. Since the early 1990s it has been sold as a nootropic dietary supplement in the United States.