title: Effects of azaperone on cardiovascular and respiratory functions in the horse.
abstract: 1 The butyrophenone tranquilizer, azaperone, was administered intramuscularly, at dose levels of 0.4 and 0.8 mg/kg, to ponies and its effects on cardiovascular and respiratory functions assessed. 2 Arterial blood pH, CO2 tension (PaCO2) and O2 tension (PaO2) remained relatively constant throughout the course of action of azaperone. 3 Azaperone did not modify plasma protein concentration but venous blood packed cell volume and haemoglobin concentration were reduced by 5 to 10% for at least 4 hours. These changes were probably caused by uptake of erythrocytes into the splenic reservoir. 4 Small increases in heart rate occurred for up to 60 min after administration of the drug, and this was followed by a slight bradycardia in some ponies. 5 Azaperone reduced mean arterial blood pressure (MAP) for at least 4 h, by which time its ataractic action was generally no longer apparent. The hypotension was caused, during the early phase of action at least, by a reduction in peripheral resistance, since cardiac output was increased slightly 20 min after its administration. Possible mechanisms underlying the cardiovascular changes are discussed. 6 In spite of reductions in arterial blood O2 content and MAP produced by azaperone, it is likely that tissue oxygenation was adequate, since arterial blood lactate concentrations were not increased.
mesh_terms: D000818:Animals; D001376:Azaperone / Q000494:pharmacology*; D001798:Blood Proteins / Q000032:analysis; D001799:Blood Sedimentation; D002090:Butyrophenones / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006454:Hemoglobins / Q000032:analysis; D006736:Horses; D007773:Lactates / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects*; D011773:Pyruvates / Q000097:blood; D013997:Time Factors; D014149:Tranquilizing Agents / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D001798:Blood Proteins; D002090:Butyrophenones; D006454:Hemoglobins; D007773:Lactates; D011773:Pyruvates; D014149:Tranquilizing Agents; D002245:Carbon Dioxide; D001376:Azaperone