Naloxone in endotoxic shock: experimental models and clinical perspective.

Naloxone has been used as a pharmacological tool to investigate the role of endorphins and opiate receptors in the cardiovascular pathophysiology of shock. It would appear that endorphins act on opiate receptors to contribute to the abnormalities found and that naloxone improves survival as well as cardiovascular function in shock. Preliminary studies in humans and the subhuman primate create cautious optimism regarding the clinical application of this information. Naloxone has served us well as a key to unlock the involvement of endorphins and opiate receptors in shock. However, further advances in our understanding may depend on the development and use of opiate receptor agonists and antagonists specific for the different opiate receptors described, each subserving different functions. Naloxone's disadvantage of increasing pain awareness may limit its clinical usefulness but might be overcome by using drugs that reverse the behavioral and neuroendocrine changes produced by beta-endorphin without altering pain relief. Thyrotropin-releasing hormone (TRH) is just such a "physiological" opiate antagonist which has been shown to increase MAP in experimental endotoxic and hemorrhagic shock [32].