<i>In Vivo</i> Detection of Nitrous Oxide in Blood and Saliva Following Recreational Use

Nitrous oxide (N₂O) is commonly used as a recreational drug, and the Dutch police have reported numerous traffic incidents related to its misuse. At the same time, the <i>in vivo</i> pharmacokinetics of N₂O remain underexplored. In light of these facts, this study aimed to detect and quantify N₂O in blood and saliva after inhalation exposure of a recreational dose. Consequently, a pilot <i>in vivo</i> study was conducted with six participants inhaling N₂O using a party balloon, comparable to urban habits. A headspace gas chromatography-mass spectrometry method was used to detect N₂O levels in blood and saliva. N₂O was detectable in both blood and saliva for over 60 min post-exposure. Concentrations in blood followed a two-phase exponential decay with a crossover time of 16.7 ± 4.7 min between the two phases. Calculated blood concentrations were found at 0.4-20 mL of N₂O/L blood. Salivary concentrations did not exhibit an exponential decay pattern and were only clearly distinguishable from baseline levels during the first 15 min, as low N₂O concentrations were also detectable in saliva of participants who had not inhaled N₂O gas. This points toward the presence of endogenous sources of N₂O giving rise to detectable concentrations in the oral cavity. This study underscores the possibility of using blood for detecting recent N₂O inhalation and highlights the need to consider background levels in saliva when interpreting results. Further research is necessary to elucidate the mechanisms underlying baseline concentrations of N₂O in the saliva matrix.