Analgesic efficacy of krypton-oxygen gas mixture inhalation in a rat model of neuropathic pain

BACKGROUND: Neuropathic pain is one of the most challenging forms of chronic pain and is often refractory to standard pharmacotherapy. Given the limited efficacy of existing therapies, inert gases have attracted interest as potential modulators of nociceptive signaling.

AIM: This work aimed to evaluate the analgesic activity of a krypton-oxygen gas mixture (KrypOx 79) in a preclinical rat model of neuropathic pain.

METHODS: The experiment was conducted in male Wistar rats (n = 40). Neuropathic pain was induced using the chronic constriction injury (CCI) model of the sciatic nerve (Bennett and Xie). Animals were randomly assigned to three groups: krypton–oxygen gas mixture 79 (n = 8), control (air mixture, n = 8), and gabapentin 372 mg/kg (n = 8). Analgesic effects were assessed by changes in mechanical sensitivity thresholds using von Frey filaments (Dixon–Chaplan method) on day 14 after model induction. Statistical analysis was performed using nonparametric tests (Kruskal–Wallis, Friedman test, Dunn post hoc correction).

RESULTS: Rats in the KrypOx 79 group demonstrated a significant 3–4–fold increase in mechanical sensitivity thresholds compared with baseline at 0 and 30 minutes after inhalation (p < 0.05). The analgesic effect gradually declined within 3–4 hours. In the gabapentin group, reduced sensitivity was observed at 3–4 hours after administration, which is consistent with its pharmacokinetic profile.

CONCLUSION: The krypton–oxygen gas mixture (KrypOx 79) produces a pronounced but short-lived analgesic effect in a model of neuropathic pain, with onset within the first 30 minutes after exposure. These findings support the potential of krypton as a fast-acting inhalational analgesic and justify further studies to investigate its mechanisms of action and possible clinical applications.