Effects of Azaperone on Cardiovascular and Respiratory Functions in the Horse

Abstract

1The butyrophenone tranquillizer, 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 02 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. 5Azaperone 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 02 content and MAP produced by azaperone, it is likely that tissue oxygenation was adequate, since arterial blood lactate concentrations were not increased.

A review of drugs and techniques used for sedation and anaesthesia in captive rhinoceros species

“…Mean arterial blood pressure is reduced via a reduction in peripheral resistance and is accompanied by a slight increase in cardiac output. 23 Azaperone produces peripheral vasodilation and reduces the hypertensive effects of etorphine and may even counteract the respiratory depression caused by etorphine. Azaperone has been used in combination with etorphine extensively in recent years for chemical restraint of free ranging and confined black 9 and white rapid inductions are preferable to minimise the risk of injuries that maybe sustained during the excitement phase.…”

Evaluation of the Effects of the Sedation with Azaperone/Acepromazine and Immobilization with Guaiphenesin/Thiopentone in Mules

“…RR is not affected in horses tranquillized separately with AC (Marroum et al, 1994) or AZ (Lees and Serrano, 1976). It is possible that the decrease of RR in the mules was due to a synergistic effect of the two drugs.…”

“…On the other hand administration of AZ or AC application independently produces slight hypotension in horses (Lees and Serrano, 1976;Marroum et al, 1994). The AZ/AC combination could produce a more intense hypotensive condition than the separate use of each substance.…”

“…Nor was it seen in mules sedated with X or X/B and anaesthetized with different combinations of K and T/Z . Early reports on the use of AZ in horses (Lees and Serrano, 1976) described moderate tachycardia with duration above 1 h, one of the drug's most attractive cardiovascular effects. It is known that this circumstance does not affect the animal's physiological state.…”

Effect of azaperone on cardiovascular responsiveness in stress‐sensitive pigs

“…Azaperone is one of the more widely used drugs for preventing these losses, and it is thought to act as a tranquillizer which exerts its effect centrally, and so reduces the liberation of catecholamines from the sympathoadrenomedullary nervous system. Besides its tranquillizing effect, azaperone has an aadrenergic blocking action in the horse (Lees & Serrano, 1976), and it is also effective in reducing mortality in rats given a potentially lethal dose of noradrenaline (Marsboom, 1971). Since a-blockade has been used successfully to aid survival in stress sensitive pigs undergoing malignant hyperthermia (Lister et al, 1976), it is possible that azaperone owes part of its beneficial effect to adrenergic blockade of a-receptors in one or more tissues.…”