Vasopressin may be useful in the treatment of systemic anaphylaxis in rabbits

Recent studies demonstrate that vasopressin is useful when treating hemorrhagic and septic shock. The effect of vasopressin on systemic anaphylaxis has not been investigated except in clinical case reports. Vasopressin increases blood pressure because of vasoconstriction through the V1 receptor. Thus, we evaluated the effect of vasopressin on circulatory depression and bronchoconstriction provoked by systemic anaphylaxis and survival rates in rabbits. In the first set of experiments, 15 nonsensitized rabbits received normal saline (control) and vasopressin at 0.8 or 0.08 U/kg. In the second set, 40 sensitized rabbits received horse serum to induce anaphylaxis, and then received the same drugs as in the first set. In the first set, mean arterial pressure (MAP) in vasopressin groups increased by 18% to 24% compared with the control. Vasopressin at 0.8 U/kg decreased MAP insignificantly before the increases of MAP occurred. In the second set, vasopressin at 0.08 U/kg improved the survival rate. At 45 min after antigen challenge, 69% of the rabbits that received vasopressin at 0.08 U/kg were alive, whereas 29% of the control rabbits and 23% of the rabbits that received vasopressin at 0.8 U/kg were alive. Vasopressin increased MAP by 36% to 109% compared with the control within 5 min, however, at 2 min, vasopressin at 0.8 U/kg had no effect on MAP. Pulmonary dynamics were similar. In conclusion, vasopressin at 0.08 U/kg improved survival rates and severe hypotension provoked by systemic anaphylaxis, suggesting that this agent may be useful in the treatment of systemic anaphylaxis.