Registration Dossier
Registration Dossier
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EC number: 233-032-0 | CAS number: 10024-97-2
Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
Approximately 5 % of inhaled nitrous oxide is absorbed by the organism. Nitrous oxide is hardly metabolized and is therefore exhaled unchanged.
Key value for chemical safety assessment
- Bioaccumulation potential:
- no bioaccumulation potential
- Absorption rate - inhalation (%):
- 5
Additional information
There are several data on pharmacokinetics and metabolism of nitrous oxide available which are summarised in the MAK value documentation (1993).
Pharmacokinetics
Approximately 5 % of inhaled nitrous oxide is absorbed by the organism (Eger 1974). Nitrous oxide is sparingly soluble in blood and is rapidly distributed. Its effects on the central nervous system develop quickly but do not last very long (Brodsky and Cohen 1986). After nitrous oxide anaesthesia, the gas is transferred rapidly from the blood into the alveoli where it dilutes the oxygen from inhaled air (diffusion hypoxia) (Fink 1955). Nitrous oxide is hardly metabolized and is therefore exhaled unchanged. Approximately 6.4 % of the amount taken up is eliminated via the skin (Stoelting and Eger 1969). Nitrous oxide diffuses more rapidly into body cavities such as the cerebral ventricle or middle ear than the nitrogen which they contain can leave the cavity; this can lead to increased pressure and ruptures (Brodsky and Cohen 1986). Transplacental transmission to the foetus has been demonstrated (Marx et al. 1970).
Metabolism
Nitrous oxide is reduced to nitrogen in the reaction with the central Co+ ion of vitamin B12 (Banks et al. 1968, Hong et al. 1980). After a single passage through the liver, however, the concentration of nitrous oxide in the blood decreases by only 0.03 % (Sawyer et al. 1977). It has been deduced from in-vitro investigations that about 0.004 % of the total nitrous oxide absorbed is metabolized in humans and animals to nitrogen by bacterial reductases in the intestine. During this process OH radicals are probably formed (Hong et al. 1980). Formation of radicals has been demonstrated in vitro in human intestinal contents incubated with nitrous oxide (Bösterling et al. 1980).
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