Preliminary assessment of midazolam, fentanyl and fluanisone combination for the sedation of rhesus macaques (Macaca mulatta)

This study was undertaken to assess the suitability of fentanyl/fluanisone ('Hypnorm', VetaPharma; 0.315mg/mL of fentanyl citrate and 10mg/mL of fluanisone) alone or combined with midazolam in rhesus macaques. Fifteen rhesus macaques requiring sedation for veterinary procedures received an intramuscular (IM) dose range of Hypnorm from 0.01mL/kg to 0.3mL/kg either alone or combined with 0.5mg/kg of midazolam. To reverse the sedation, flumazenil in combination with either naloxone, buprenorphine or butorphanol was administered intravenously (IV) or IM. Rhesus macaques were successfully sedated with 0.1mL/kg of Hypnorm and 0.5mg/kg of midazolam, and sedation was partially reversed by the administration of flumazenil and either naloxone or buprenorphine. However the primates remained slightly sedated and were only released into their home cage several hours post recovery. Butorphanol failed to induce recovery and caused marked respiratory depression. The neuroleptanalgesic combination, Hypnorm and midazolam, effectively immobilized rhesus macaques and was reversible with a combination of flumazenil and either naloxone or buprenorphine.