Concentration and Detection Time of Nitrous Oxide in Blood Following Controlled Inhalation.

Area of Science:

• Forensic Toxicology
• Pharmacokinetics
• Neuroscience

Background:

• Recreational nitrous oxide (N₂O) use is increasing, particularly among drivers.
• Concerns exist regarding N₂O's impact on driving safety and its detectability.
• Limited data is available on N₂O blood concentrations and persistence post-use.

Purpose of the Study:

• To investigate the pharmacokinetics and blood detectability of nitrous oxide (N₂O) after controlled administration.
• To determine the duration N₂O remains detectable in blood following recreational use.

Main Methods:

• 11 volunteers received a controlled 10-minute inhalation of 50% N₂O.
• Blood samples were collected and analyzed for N₂O using headspace-gas chromatography-mass spectrometry (HS-GC-MS).
• Pharmacokinetic modeling was employed to describe N₂O elimination.

Main Results:

• N₂O elimination followed a two-compartment model with half-lives of 2.4 and 31 minutes.
• N₂O was detectable in blood for an average of 62 minutes at a 0.2 mL/L cutoff.
• N₂O remained detectable for 132 minutes at a 0.05 mL/L cutoff, despite rapid dissipation of effects.

Conclusions:

• Nitrous oxide (N₂O) can be detected in blood for a significant period after use, exceeding the duration of its psychoactive effects.
• The prolonged detectability of N₂O in blood has implications for driving safety and impaired driving investigations.
• Further research is needed to establish definitive blood concentration thresholds for N₂O impairment in driving contexts.