Comparative evaluation of anesthetic effects of medetomidine–midazolam–butorphanol and medetomidine–remimazolam–butorphanol administered subcutaneously and intraperitoneally in C57BL/6J mice

Anesthesia management in experimental animals is essential for animal welfare and data reproducibility. In Japan, medetomidine-midazolam-butorphanol (MMB) is commonly used due to ketamine restrictions. We developed medetomidine-remimazolam-butorphanol (MRB) by replacing midazolam with remimazolam for faster metabolism and recovery. This study compared MMB and MRB administered intraperitoneally (i.p.) or subcutaneously (s.c.) in C57BL/6J mice of both sexes. Induction and recovery were assessed using immobilization, loss of righting reflex, and return of righting reflex. MRB i.p. produced the fastest induction and recovery with relatively low variability, suggesting potential utility for brief procedures. In contrast, s.c. administration resulted in consistent onset and recovery profiles for both agents, which may be advantageous for routine experimental use.