Treatment of
cyanide poisoning generally includes
methemoglobin forming agents, like
amyl nitrite and/or
sodium nitrite (SN), in combination with
sodium thiosulphate (STS). However, in many instances of
cyanide poisoning, use of
nitrites are contraindicated due to their strong vasoactive properties.
alpha-Ketoglutarate (alpha-KG) antagonises
cyanide by
cyanohydrin formation and is considered a promising
antidote for
cyanide poisoning. In the present study, pre-treatment (30 min) and simultaneous treatment (0 min) of alpha-KG (5 mM) was found to confer significant protection against 5 mM
potassium cyanide (KCN) induced cytotoxicity in rat thymocytes as measured by
eosin Y exclusion and leakage of intracellular
lactate dehydrogenase (LDH), but could not prevent the
mitochondrial dysfunction (MTT assay), depletion of cellular GSH (
reduced glutathione) and DNA damage. The post-treatment (5 or 30 min) of alpha-KG did not offer any protection on any of the above parameters. Results of in vitro studies were also supported by in vivo data. Pre-treatment of peroral (p.o.) alpha-KG (0.125-2.0 g/kg) exhibited dose and time dependent effects and was found to be effective even when given upto 60 min prior to KCN (p.o.). Addition of STS significantly enhanced the protective efficacy of alpha-KG at all the doses and time intervals.
A 10 min pre-treatment of alpha-KG increased the LD(50) of KCN 7.6-fold, which was further increased to 25.6-fold by the addition of both SN and STS. Simultaneous treatment of alpha-KG (2.0 g/kg) increased the LD50 of KCN 5.4-fold which was increased to 18.1-fold by the addition of STS. However, addition of SN did not confer any additional protection. In the presence of SN+STS, a decrease in the dose of alpha-KG exhibited a dose-dependent decrease in protection, but still
a >10-fold protection could be observed at 1.0 g/kg dose of alpha-KG. Considering the efficacy and safety of peroral alpha-KG, a promising treatment regimen consisting of alpha-KG+STS or alpha-KG+SN+STS is proposed, depending upon the individual situation.