In Vivo 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 in vivo 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 in vivo 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.