extended-release preparations Activated charcoal therapy may be used for adsorption of gastric APAP, using the same guiding principles for charcoal administration discussed in the general approach section of this chapter In addition to an APAP level, initial diagnostic testing should include baseline hepatic transaminases, chemistries, and consideration of screening for coingestants For patients presenting to care within 24 hours of a single acute overdose at a known time of ingestion, a nomogram ( Fig 102.2 ) is available for using the plasma APAP level in the prediction of likely toxicity We recommend using the lower line of the nomogram, plotted 25% below the probable toxicity line, to err on the safe side in making management decisions Importantly, the nomogram is not validated for chronic APAP toxicity and caution should be taken in interpreting the nomogram in the setting of coingestants that may be associated with decreased GI motility In the setting of chronic supratherapeutic ingestion, multiple ingestions, and unknown time of ingestion, the Rumack-Matthew nomogram cannot be used to guide management In these settings, an undetectable acetaminophen level, normal transaminases, and normal INR exclude significant toxicity However, a detectable acetaminophen level and/or evidence of hepatotoxicity should prompt treatment with NAC N -acetylcysteine (NAC), given IV or orally, is most effective at ameliorating hepatotoxicity when instituted within hours of ingestion It also lessens the severity of hepatic damage if used in the setting of clinical presentation beyond hours The major adverse reaction associated with IV NAC is the occurrence of anaphylactoid reaction, which typically occurs during the relatively higher-dose loading infusion Clinicians administering IV NAC should be skilled at recognizing and treating anaphylactoid reactions and should be particularly cautious when using this route in patients with a history of asthma Although rarely done, the inhalational form of NAC can be administered enterally and can be mixed with fruit juice or soda to disguise its foul smell, or it can be administered by NG tube Only mild GI side effects result from its use, but persistent vomiting is an occasional obstacle to completing the course of oral therapy This may be obviated by giving the dose slowly or by NG or duodenal tube infusion Antiemetic therapy may also be helpful The protocol for NAC therapy may be summarized as follows: Consider GI decontamination options as noted in the previous section If the patient presents less than hours after a single acute ingestion, wait to draw 4-hour level and base therapeutic decision on nomogram (assumes rapid turnaround time so level will be available by to hours after ingestion); if necessary, initiate treatment as described next For extended-