Medetomidine Administration at the Subcutaneous GV20 Acupoint Compared with the Intramuscular Route in Guinea Pigs (Cavia porcellus): Sedation Score, Onset, and Duration of Action

Recent research in both humans and animals has explored alternative routes for drug administration, such as pharmacopuncture, a technique involving the subcutaneous administration of low drug doses at acupuncture points. Among these points, the Governing Vessel 20 (GV20) has attracted particular interest in veterinary medicine due to its reported tranquilizing and sedative effects in humans and dogs. It has been proposed that administering sedative agents at this site may potentiate their effects, allowing for dose reduction while maintaining efficacy and minimizing adverse reactions. This study aimed to compare the sedative effects of medetomidine administered at the GV20 acupoint compared with the intramuscular route in adult guinea pigs (Cavia porcellus). Twenty animals received medetomidine (100 µg/kg) via both routes in a crossover design with a 2-week washout period. Sedation was assessed using a previously published scale (0-19). Sedation onset was defined as the time to achieve a score >3 of 19, and duration as the time to return to ≤3 of 19. Assessments were performed before and after administration at 1-minute intervals for the first 10 minutes, then every 2 minutes up to 30 minutes, and every 5 minutes thereafter until recovery. Comparisons of maximum sedation score, onset, and duration between routes were analyzed using the Wilcoxon signed-rank test. No significant differences were found in the maximum score, time to onset, or duration of sedation between the GV20 and intramuscular routes. These results indicate that, under the conditions of this study, medetomidine administration at GV20 did not enhance sedative efficacy or prolong the duration of action compared with the intramuscular route.