Evaluation of butorphanol, medetomidine and midazolam as a reversible narcotic combination in free-ranging African lions (Panthera leo)

ObjectiveTo evaluate the effects of the combination butorphanol, medetomidine and midazolam (BMM) and its reversibility in lions.Study designProspective clinical trial.AnimalsThirty free-ranging lions, 10 male and 20 female, weighing 81-210 kg.MethodsLions were immobilised with butorphanol mean 0.31 ± SD 0.034 mg kg^?1, medetomidine 0.052 ± 0.006 mg kg^?1, midazolam 0.21 ± 0.024 mg kg^?1 and hyaluronidase 1250 IU administered intramuscularly with a dart gun. Upon recumbency, physiological parameters and anaesthetic depth were monitored 10-15 minutes after darting (T1) and repeated every 10 minutes for a further 30 minutes (T2, T3, T4). Arterial blood gas analyses were performed at T1 and T4. At the end of the procedure, 45-60 minutes after initial darting, immobilisation was reversed with naltrexone 0.68 ± 0.082 mg kg^?1, atipamezole 0.26 ± 0.031 mg kg^?1, and flumazenil 0.0032 ± 0.0007 mg kg^?1 administered intravenously and subcutaneously.ResultsThe BMM combination rapidly induced immobilisation and lateral recumbency was reached within 7.25 ± 2.3 minutes. Median induction score scored 1 (excellent) to 4 (poor)] was 1.4 (range 1-2). Cardio-respiratory parameters were stable. Heart rate varied from 32 to 72 beats per minute, respiratory rate from 14 to 32 breaths minute^?1 and rectal temperature from 36.6 to 40.3 °C. No sudden arousals were observed. Arterial blood gas analyses revealed a mean pH of 7.33, PaCO₂ of 33 mmHg and PaO₂ of 87 mmHg. Mild to moderate hypoxemia was seen in four lions. Recovery was smooth and lions were walking within 4.4 ± 4.25 minutes. Median recovery score scored 1 (excellent) to 4 (poor)] was 1.3 (range 1-2).Conclusion and clinical relevanceThe drug combination proved to be effective in immobilising free-ranging healthy lions of both sexes with minimal cardio-respiratory changes.