Influence of idazoxan on the respiratory blood gas changes induced by alpha 2-adrenoceptor agonist drugs in conscious sheep.

Administration of either xylazine (50 micrograms/kg) or detomidine (10 micrograms/kg) caused a significant degree of arterial hypoxaemia in six conscious sheep. This effect was independent of any changes produced by changes in posture as all the sheep remained standing. Administration of the specific alpha 2-antagonist drug idazoxan (0.1 mg/kg bodyweight) five minutes before injection of either of the drugs completely abolished the hypoxaemia. These results lend support to the view that the respiratory effect of these drugs is mediated via alpha 2-adrenoceptor activity.