Definition of antipyresis

As described in Chapter 1, in true fever the thermoregulatory system behaves as though there is a body temperature set point which is raised as part of the febrile process. Thus, in the plateau phase of fever raising or lowering the body core temperature evokes defence responses similar to those evoked at the ‘normal’ body temperature. In the febrile condition, as defined thus, administration of some drugs lowers the apparent set point for body temperature regulation and consequently reduces the body temperature. In other conditions, e.g., artificial body heating, exposure to high environmental heat stress, and more controversially during exercise, the body core temperature is raised but the apparent body temperature set point is not. Drugs that act to reduce true febrile temperature and which do not have an effect on normal body temperature or on the cooling rate of artificially, but not pathologically raised core temperature, are known as antipyretics. Some drugs are capable of reducing the core temperature without resetting the apparent set point, e.g., substances which under any circumstances will induce massive peripheral vasodilatation or profuse sweating may act to reduce core temperature in fever or under afebrile conditions. Amidopyrine, which has been used as an antipyretic, does cause a fall in core temperature in the afebrile rabbit, in a dose-dependent manner, with the maximum fall in core temperature in response to 100 mg intravenously of 0.35 °C (Grundmann, 1969).