Hydroxocobalamin monohydrochloride (Vitamin B12a monohydrochloride) is an injectable naturally occurring form of vitamin B12 with a favorable adverse effect profile, used as a dietary supplement in the treatment of vitamin B12 deficiency including pernicious anemia[1][2].
The cobalt atom of hydroxocobalamin binds cyanide and nitric oxide and hydroxocobalamin attenuates vascular responses to NO in vitro[3].
Treatment with hydroxocobalamin before or after giving LPS attenuates LPS-induced hypotension and increases in plasma RNI and enhances LPS-induced urinary excretion of RNI. Hydroxocobalamin (20 mg/kg i.p.) given to Swiss-Webster mice 30 min before giving LPS (16 mg/kg i.p.) decreases the 24-hr mortality of LPS from 80 to 50% and the 36- and 96-hr mortality from 100 to 60% (hydroxocobalamin)[3]. More than 60% of the mice administered 35 mg/kg (0.63 mmol/kg) of NaSH (LD90) survive (at 24 h) when hydroxocobalamin (0.25 mmol/kg) is given after NaSH administration whereas less than 15% of the mice survive without hydroxocobalamin. Hydroxocobalamin (50-100 μM) or cobalt (50-100 μM) also preventes hepatocyte cytotoxicity induced by NaSH (500 μM). Furthermore, adding hydroxocobalamin 60 min later than NaSH still shows some protective activity[4].
[1]. Cheungpasitporn W, et al. High-dose hydroxocobalamin for vasoplegic syndrome causing false blood leak alarm. Clin Kidney J. 2017 Jun;10(3):357-362. [2]. Wang H, et al. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database Syst Rev. 2018 Mar 15;3:CD004655. [3]. Greenberg SS, et al. Hydroxocobalamin (vitamin B12a) prevents and reverses endotoxin-induced hypotension and mortality in rodents: role of nitric oxide. J Pharmacol Exp Ther. 1995 Apr;273(1):257-65. [4]. Truong DH, et al. Prevention of hydrogen sulfide (H2S)-induced mouse lethality and cytotoxicity by hydroxocobalamin (vitamin B(12a)). Toxicology. 2007 Dec 5;242(1-3):16-22.