Naloxone can reverse acute opiate intoxication. If the patient is narcotic tolerant it may precipitate opiate withdrawal. Conventional teaching holds that opiate withdrawal is a nuisance but never life threatening. But that's passive withdrawal. Precipitated withdrawal, as might occur with naloxone given to a narcotic tolerant patient, may be more problematic as it is associated with profuse vomiting and catecholamine surge. More here from Emergency Medicine News.