# A patient arrives at the emergency department after ingesting an unknown amount of acetaminophen 4 hours ago. The patient is alert and oriented but reports nausea and vomiting. Which antidote should the nurse prepare to administer? > source: MyMerci (mymerci.kr) > url: https://mymerci.kr/pages/nclex_q.php?qn_id=540363 > language: ko > subject: Adult Health ## 문제 A patient arrives at the emergency department after ingesting an unknown amount of acetaminophen 4 hours ago. The patient is alert and oriented but reports nausea and vomiting. Which antidote should the nurse prepare to administer? A 28-year-old patient presents to the emergency department with a history of acetaminophen overdose approximately 4 hours prior to arrival. The patient appears alert and cooperative but complains of persistent nausea and has vomited twice since arrival. ## 보기 1. Flumazenil 2. Naloxone 3. N-acetylcysteine **✔ 정답** 4. Activated charcoal **정답: 3** ## 해설 N-acetylcysteine is the specific antidote for acetaminophen poisoning and is most effective when administered within 8-10 hours of ingestion. Acetaminophen overdose is a common cause of acute liver failure and requires prompt recognition and treatment. The toxic metabolite NAPQI (N-acetyl-p-benzoquinone imine) is normally detoxified by glutathione, but in overdose situations, glutathione stores become depleted, leading to hepatocyte necrosis. N-acetylcysteine (NAC) is the specific antidote for acetaminophen poisoning. It works by replenishing glutathione stores and providing an alternative pathway for NAPQI detoxification. The effectiveness of NAC is time-dependent, with maximum benefit when given within 8-10 hours of ingestion, though it can still provide benefit up to 24 hours post-ingestion. This patient presents 4 hours post-ingestion, which is within the critical time window for optimal NAC effectiveness. Early symptoms of acetaminophen toxicity include nausea, vomiting, and malaise, which this patient is experiencing. The nurse should prepare NAC for immediate administration as delay can significantly impact patient outcomes. Treatment typically involves oral or intravenous NAC administration over 20-21 hours with dosing based on patient weight and time since ingestion. Monitoring includes serial acetaminophen levels, liver function tests, and assessment for signs of hepatotoxicity. ## 심화 해설 Clinical Context and Pathophysiology The patient’s presentation—ingestion of an unknown amount of acetaminophen approximately 4 hours prior, accompanied by nausea and vomiting—is a classic early manifestation of acetaminophen toxicity. Acetaminophen is responsible for more pharmaceutical overdoses than any other medication in the United States and is the leading cause of acute liver failure [3]. In therapeutic doses, acetaminophen is primarily metabolized via glucuronidation and sulfation. However, in overdose, these pathways become saturated, shunting metabolism toward the cytochrome P450 system, which produces the highly reactive and hepatotoxic metabolite N-acetyl-p-benzoquinone imine (NAPQI). NAPQI is normally detoxified by conjugation with hepatic glutathione, but once glutathione stores are depleted, NAPQI binds to hepatocellular proteins, causing centrilobular necrosis and potentially severe acute liver failure [1]. Antidote Mechanism and Rationale The correct antidote is N-acetylcysteine (NAC). Introduced as an antidote in 1974, NAC has revolutionized the management of acetaminophen poisoning by significantly reducing hepatotoxicity and associated mortality [1]. NAC works through multiple mechanisms: it serves as a glutathione precursor, replenishing depleted hepatic glutathione stores to detoxify NAPQI; it directly conjugates with NAPQI; and it may have antioxidant and hemodynamic effects. The standard treatment involves a three-bag intravenous protocol, though recent research has explored abbreviated 12-hour infusions compared to the traditional 20-hour regimen [4]. While NAC is widely considered safe when administered appropriately, the nurse must be vigilant, as improper administration—such as iatrogenic overdose—has been associated with serious adverse outcomes including cerebral edema and hemolytic uremic syndrome [2]. Analysis of Incorrect Options - Flumazenil is a benzodiazepine receptor antagonist used to reverse benzodiazepine overdose. It has no role in acetaminophen toxicity and could precipitate seizures in patients with unknown co-ingestions. - Naloxone is an opioid receptor antagonist indicated for opioid overdose. While many combination products contain both acetaminophen and opioids, naloxone does not address the hepatotoxic threat of acetaminophen itself [3]. - Activated charcoal may be considered for gastrointestinal decontamination if the patient presents within 1 to 2 hours of ingestion. At 4 hours post-ingestion, its benefit is significantly diminished, and it is not an antidote for the systemic toxicity that has already begun. NAC remains the priority intervention. Nursing Considerations and Clinical Judgment The nurse should anticipate preparing NAC for intravenous administration based on the patient’s weight and the institution’s protocol. Given the patient’s persistent nausea and vomiting, the nurse must recognize that antiemetic administration may be necessary to facilitate NAC tolerance, as vomiting is a common side effect of both the toxicity and the antidote infusion. The nurse should also prepare to draw a serum acetaminophen level, liver function tests, and coagulation studies to plot on the Rumack-Matthew nomogram, which guides the necessity and duration of NAC therapy. The presence of acetaminophen protein adducts in circulation serves as a highly sensitive biomarker of oxidation and potential hepatic injury, confirming the need for continued monitoring even after antidote completion [4].References (research sources) - [1][Translated article] N-acetylcysteine: 50 years since the discovery of an antidote that has changed the prognosis of acetaminophen poisoning.Research articleNogué-Xarau S, Martínez-Sánchez L, García-Peláez M, Fernández de Gamarra-Martínez E, Pi-Sala N, Gispert-Ametller À, Salgado-García E, Aguilar-Salmerón R. (2026) · DOI: 10.1016/j.farma.2025.10.015 - [2]Safety of acetylcysteine: a scoping review of iatrogenic overdose cases and their associated complications.Research articleBaker MB, Young J, Binda DD, Dienes E, Kennedy JM. (2026) · DOI: 10.1080/15563650.2026.2673132 - [3]Acetaminophen ToxicityResearch articleSchaffer DH, Murray BP, Khazaeni B. (2026) - [4]Paracetamol adducts following overdose treated with a shorter acetylcysteine infusion: findings from the NACSTOP 2 trial.Research articleWong A, James LP, McNulty R, Gunja N, Graudins A. (2026) · DOI: 10.1080/15563650.2026.2655388 ## 임상 시나리오 Clinical Management of Acetaminophen Overdose Assessment & Monitoring - Obtain a detailed history: time of ingestion, amount, co-ingestants, and formulation (immediate vs. extended-release). - Draw a serum acetaminophen level 4 hours post-ingestion or as soon as possible thereafter. Plot the level on the Rumack-Matthew nomogram to determine risk of hepatotoxicity and need for antidotal therapy. - Monitor baseline liver function tests (AST, ALT, bilirubin, INR), renal function (BUN, creatinine), and electrolytes. Repeat at least daily in significant ingestions. Antidote Administration: N-acetylcysteine (NAC) - Initiate NAC as early as possible, ideally within 8 hours of ingestion, for maximal hepatoprotection. It is still beneficial if started later in patients with evidence of liver injury. - The standard intravenous protocol is a three-bag regimen: Loading dose of 150 mg/kg in 200 mL of D5W over 60 minutes, followed by 50 mg/kg in 500 mL over 4 hours, then 100 mg/kg in 1000 mL over 16 hours. - Monitor for anaphylactoid reactions (flushing, urticaria, bronchospasm, hypotension), which are rate-related and managed by temporarily stopping or slowing the infusion and administering antihistamines. Supportive Care & Complications - Manage nausea and vomiting with antiemetics (e.g., ondansetron) to facilitate oral intake and NAC administration if the oral route is chosen. - Activated charcoal (1 g/kg) may be considered if the patient presents within 1-2 hours of a massive ingestion and has a protected airway, but it does not replace NAC. - Consult a hepatologist or poison control center (1-800-222-1222) for guidance. Prepare for potential transfer to a liver transplant center if criteria for acute liver failure develop (e.g., encephalopathy, coagulopathy). ## 핵심 개념 - **Acetaminophen Overdose** — Overdose of acetaminophen (analgesic/antipyretic). The main toxicity is delayed hepatocellular necrosis caused by the NAPQI metabolite. - **N-acetylcysteine** — Specific antidote for acetaminophen poisoning. Replenishes glutathione stores and detoxifies the toxic metabolite (NAPQI). - **Antidote** — An antidote for a specific toxin or poisoning. It is a substance that inhibits or neutralizes the action of the poison. - **Hepatotoxicity** — Hepatotoxicity. It is the most serious complication of acetaminophen poisoning and can cause liver cell damage and liver failure. - **Time-dependent Treatment** — Time-dependent treatment. A treatment method where the timing of initiation has a decisive impact on patient prognosis (e.g., NAC administration in acetaminophen overdose). ## 같은 주제 문제 - [A patient arrives at the emergency department after ingesting an unknown amount of acetami…](https://mymerci.kr/pages/nclex_q.php?qn_id=540352) - [A patient arrives at the emergency department after ingesting an unknown amount of acetami…](https://mymerci.kr/pages/nclex_q.php?qn_id=540353) - [A patient presents to the emergency department with suspected organophosphate poisoning fr…](https://mymerci.kr/pages/nclex_q.php?qn_id=540354) - [A patient arrives at the emergency department after ingesting an unknown amount of acetami…](https://mymerci.kr/pages/nclex_q.php?qn_id=540355) - [A nurse is caring for a patient who has just received naloxone for the reversal of a suspe…](https://mymerci.kr/pages/nclex_q.php?qn_id=540356) - [The nurse is monitoring a patient following naloxone administration for opioid overdose re…](https://mymerci.kr/pages/nclex_q.php?qn_id=540357) - [A nurse is caring for a patient who received an overdose of warfarin and is experiencing s…](https://mymerci.kr/pages/nclex_q.php?qn_id=540358) - [The nurse should monitor the patient most closely for which potential complication followi…](https://mymerci.kr/pages/nclex_q.php?qn_id=540359) --- More free questions: [기출문제](https://mymerci.kr/) _학습 참고용입니다. 실제 임상은 최신 지침과 소속 기관 프로토콜을 따르세요._