Pyritinol is a semi-water soluble compound that is constructionally similar to Vitamin B6. Essentially, it is two pyridoxine(B6) molecules mirroring each other, in which they are bond not by their phosphorus side chains but instead a disulfide bridge. It is commonly sold as pyritinol hydrochloride, or pyrithioxine hydrochloride.
It is implicated in recovery and repair of damaged cholinergic neurons and may increase acetylcholine levels and uptake through lipid soluble metabolites. It also increases glucose utilization and cGMP levels in the brain, although more clinically significant in aged subjects.
It has been noted that these studies have their validity questioned due to small sample sizes. Most literature has also been published in the 1980s and has not been replicated to a large degree.
Pyritinol can stimulate neutrophil function and cause an increase in neutrophil cGMP levels.
It has been used with moderate success in vivo for reduction of symptoms associated with rheumatoid arthritis.
Pyritinol is sometimes marketed as an anti-hangover pill through its prostaglandin inhibitory effects which result in a prevention of methanol and formeldehyde induced inflammation. Only one study has been directly recorded, which showed some benefit.
Pyritinol has been linked to, and causality established, case study of acute pancreatitis (inflammation of the pancreas), the subject took 600mg daily for 3 months leading up to the initial inflammatory reaction, and then subsequent reactions were induced with minimal dosing. It has been linked to causing acute hepatitis (inflammation of the liver) as well in over 5 case studies averaging 400-600mg daily and experiencing jaundice and hepatitis within 2 weeks of starting usage. The mechanism of action for pyritinol's hepatotoxicity appears to be due to individual physiology (not applicable to everybody) and cholestatic in nature.
It has historically been linked to drug-induced pemphigus and occupational-contact dermatitis and other topical outbursts have been noted. A single case of auto-immune hypoglycemia has also been recorded.
Most of these side effects are due to pyritinol belonging to a class of sulfhydryl compounds.
Given its usage in Europe for over twenty years for medicinal treatment, it is unlikely that these effects manifest themselves in the majority of persons; equally likely is underreporting in the past of pyritinol-induced hepatitis.