Prolonged depression of thermoregulation after xylazine administration to cats

Xylazine administered subcutaneously (s.c.; 1–4 mg/kg) or intravenously (i.v.; 0.5-2 mg/kg) to cats consistently caused dose-related decreases in body temperature which were maximal 3–4 h after injection and lasted for at least 12 h. Otherwise the animals appeared to have recovered fully from the central nervous system effects of the drug within 1.5–3.5 h. Xylazine-induced hypothermia developed more rapidly in cats placed in a 4°C environment and, in contrast, was replaced by a hyperthermic response in cats placed in a 32°C environment. These changes in body temperature were not opposed by compensatory thermoregulatory effector activity such as shivering or tachypnea. This pattern of responses at varied environmental temperatures is indicative of a general depression of the thermo-regulation. Thus, animals given xylazine should not be exposed to extreme heat or cold for several hours to avoid development of hyper- or hypothermia.