pure reduced glutathione 60c by Encapsulations a compound containing a sulfhydryl (SH) group Glutathione 500 mg Quick-Release Capsules
Description
It is most often based on the clinical symptoms together with laboratory assessment (low serum vitamin B 12 level and elevated serum homocysteine or methylmalonic acid level) and the response to treatment to make definitive diagnosis

Unfortunately, theres a ton of confusion about this

10.1093/femsre/fuu008 FEMS Microbiol

Several patents are available for drug delivery via the nasal route to either directly target the CNS, or by systemic transport of the drugs by the nasal route to target the CNS
