Myelotoxic, neurotoxic and reproductive adverse effects of nitrous oxide.

N2O is a relatively safe general anaesthetic under normal medical and dental anaesthetic use. It is more likely to produce megaloblastosis or neuropathy when used repetitively or for periods longer than 3 hours or in individuals with vitamin B12 deficiencies. The mechanism responsible for its myelotoxicity, neurotoxicity and most likely its reproductive toxicity, involves its inhibition of MetSyn and the resulting reduction in SAM and THF levels. Administration of folinic acid or methionine have been shown to protect against megaloblastosis and neurotoxicity occurring following N2O administration. Occupational N2O exposure of medical and dental personnel during its use as an analgesic is not likely to produce adverse reproductive outcomes except in B12-deficient individuals or in those routinely exposed to high N2O levels.