Naloxone (Narcan) is generally considered to be a narcotic antagonist devoid of pharmacologic activity except for its reversal of opioid (narcotic) effects. Case reports indicate that naloxone in its role of narcotic antagonist may induce hypertension, pulmonary edema, atrial and ventricular arrhythmias, or cardiac arrest in certain patients, particularly those with pre-existing cardiac abnormalities. These adverse effects of naloxone may be due to extreme sympathetic nervous system activity resulting from the reversal of narcotic analgesia, an effect of the drug on peripheral or central opioid receptors or a drug interaction with other anesthetic agents. Any patient given naloxone, particularly in the presence of surgical pain, should be closely monitored for adverse cardiovascular effects.