Pyritinol also called pyridoxine disulfide or pyrithioxine (European drug names Encefabol, cerbon 6) is a semi-natural water soluble analog of vitamin B-6 (Pyridoxine hcl). It was produced in the 1961 by Merck Laboratories by bonding 2 B-6 compounds (pyridoxine) together with a disulfide bridge. Since the 1970s has been a prescription drug in several countries for cognitive disorders and learning disorders in children. Since the early 90's it has been sold as a dietary supplement in the US as a nootropic.

Adverse effects include nausea, headache, and rarely allergic reaction. A 2004 survey of six case reports suggested a link between pyritinol and severe cholestatic [[hepatitis] when on several drugs for certain diseases].