Antipyresis and fever.

While understanding of the mechanisms of fever has progressed in recent years, much uncertainty remains as to whether fever in itself (as distinct from its cause) is beneficial or harmful, and what circumstances warrant antipyretic therapy. This review was designed to identify studies providing information on the effects of fever and of pharmacologic and physical therapy. Fever or analogous behavioral thermal upregulation apparently has positive effects on defense against infection in some animal models. Retrospective studies in humans suggest that failure to mount a febrile response is associated with poor outcome in certain infections but do not establish a causal relationship. Induction of fever apparently had therapeutic value in infections such as syphilis before specific antimicrobials were developed. Fever may have deleterious effects in the context of borderline cardiovascular or neurologic function or pregnancy, but data in most instances cannot separate effects of fever per se from that of underlying disease. Antipyretic drugs are effective in diminishing fever, but they have significant side effects and may suppress signs of ongoing infection. Physical cooling is important when physiologic thermoregulatory mechanisms are overwhelmed, but may sometimes increase discomfort and metabolic stress in fever. Antipyretic therapy should not be instituted routinely for every febrile episode but should be based on evaluation of relative risks in the individual case and reassessed if anticipated benefits are not achieved.