Detection of thiocyanate in postmortem blood of a fatal potassium thiocyanate-poisoning patient using gas chromatography-mass spectrometry.

Thiocyanate is an inorganic compound used in industrial applications. Here, we report a case of suicidal death due to acute thiocyanate overdose. A 44-year-old man who consumed an unknown amount of thiocyanate solution was transferred to the emergency room and died 2 h after admission. An autopsy was performed 2 days after death. General toxicological analysis of blood using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry found no drug or alcohol. Quantification using GC-MS post-derivatization with pentafluorobenzyl bromide revealed 2,290 and 1,920 mg/L of thiocyanate in the heart and femoral blood samples, respectively. Thus, the cause of death was attributed to thiocyanate overdose. This study provides useful information for the interpretation of thiocyanate-related fatalities.

Sodium bicarbonate treatment for QRS widening in bupropion overdoses.

INTRODUCTION: Bupropion cardiotoxicity widens QRS complexes by inhibiting cardiac gap junctions. Sodium bicarbonate is the standard treatment for QRS widening from sodium channel blockade, but its effect on QRS widening in bupropion cardiotoxicity is not well-studied. METHODS: This is a retrospective cohort study of bupropion overdoses from 10 hospitals between January 2010 and June 2022. Patients with documented administration of sodium bicarbonate and QRS duration > 100 milliseconds on pre-bicarbonate electrocardiogram were included. Patients with no electrocardiogram within four hours of treatment or with baseline pre-overdose wide QRS and < 10 milliseconds widening from baseline were excluded. The primary outcome was a change in QRS duration between the pre-bicarbonate electrocardiogram and the first electrocardiogram after initial bicarbonate administration. Secondary outcomes included prevalence of post-bicarbonate QRS < 100 milliseconds, change in electrocardiogram intervals after total bicarbonate administration, and change in metabolic parameters and hemodynamics. Wilcoxon signed-rank testing was performed on the primary outcome. Linear regression modeling was performed to test for an association between change in QRS and bicarbonate dosing. RESULTS: Thirteen patients were included for final analysis. The median age was 32 years, and 54% were male. Six patients developed seizures; one developed ventricular tachycardia, and four received vasopressors. The median QRS and QTc pre-bicarbonate were 116 and 495 milliseconds, respectively. The median change in QRS duration was -2.0 milliseconds, which was not statistically significant (P = 0.42). The median bicarbonate dose administered before the first post-bicarbonate electrocardiogram was 100 milliequivalents. We did not identify an association between QRS change and bicarbonate dosing (P = 0.9, R-squared = 0.001). No patient had a QRS duration < 100 milliseconds after the initial bicarbonate dose. There was minimal change in QTc, electrolytes, heart rate, or blood pressure; alkalemia post-bicarbonate was achieved in eight patients. CONCLUSION: Sodium bicarbonate did not significantly decrease QRS duration in this small retrospective cohort of bupropion overdoses.

Intravenous Acetaminophen Overdose in an Infant With Toxicokinetic Data.

CASE REPORT: A 12-month-old (former 24 week gestational age), 8.7 kg male was hospitalized after an uneventful colostomy reversal. In the postoperative unit, the patient unintentionally received 1000 mg IV (114.9 mg/kg) acetaminophen instead of the intended 100 mg IV. Serial acetaminophen concentrations were drawn. The patient received IV Nacetylcysteine and ultimately had no adverse outcomes. DISCUSSION: This case report adds to the existing literature regarding toxicokinetics of IV APAP in infants. Our patient had a calculated ke of 0.263 h-1, correlating with a half-life of 2.63 hours. Based on current available data, the half-life of IV APAP in infants varies (2.6 to 4.9 hours). The reason for this variation is unknown and further research is needed in this area.

Fifty years of paracetamol (acetaminophen) poisoning: the development of risk assessment and treatment 1973-2023 with particular focus on contributions published from Edinburgh and Denver.

INTRODUCTION: Fifty years ago, basic scientific studies and the availability of assay methods made the assessment of risk in paracetamol (acetaminophen) poisoning possible. The use of the antidote acetylcysteine linked to new methods of risk assessment transformed the treatment of this poisoning. This review will describe the way in which risk assessment and treatments have developed over the last 50 years and highlight the remaining areas of uncertainty. METHODS: A search of PubMed and its subsidiary databases revealed 1,166 references published in the period 1963-2023 using the combined terms "paracetamol", "poisoning", and "acetylcysteine". Focused searches then identified 170 papers dealing with risk assessment of paracetamol poisoning, 141 with adverse reactions to acetylcysteine and 114 describing different acetylcysteine regimens. To manage the extensive literature, we focused mainly on contributions made by the authors during their time in Edinburgh and Denver. DOSE AND CONCENTRATION RESPONSE: The key relationship between paracetamol dose and toxicity risk was established in 1971 and led to the development of the Rumack-Matthew nomogram from data collected in Edinburgh. MECHANISMS OF TOXICITY: A series of papers on the mechanisms of toxicity were published in 1973, and these showed that paracetamol hepatotoxicity was caused by the formation of a toxic intermediate epoxide metabolite normally detoxified by glutathione but which, in excess, was bound covalently to hepatic enzymes and proteins. An understanding of the relationship between the rate of paracetamol metabolism, paracetamol concentration, and toxic hazard in humans soon followed. ANTIDOTE DEVELOPMENT AND EFFICACY IN PATIENTS: These discoveries were followed by the testing of a range of sulfhydryl-donors in animals and "at risk" patients. Acetylcysteine was developed as the lead intravenous antidote in the United Kingdom. The license holder in the United States refused to make an intravenous formulation. Thus, oral acetylcysteine became the antidote trialed in the United States National Multicenter Study. Intravenous acetylcysteine regimens used initially in the United Kingdom and subsequently in the United States used loading doses of 150 mg/kg over 15 minutes or one hour, 50 mg/kg over four hours, and 100 mg/kg over 16 hours. These regimens were associated with adverse drug reactions (nausea, vomiting and anaphylactoid reactions) and hence, treatment interruption. Newer dosing regimens now give loading doses more slowly. One, the Scottish and Newcastle Anti-emetic Pretreatment protocol, using an acetylcysteine regimen of 100 mg/kg over two hours followed by 200 mg/kg over 10 hours, has been widely adopted in the United Kingdom. A cohort comparison study suggests this regimen has comparable efficacy to standard regimens and offers opportunities for selective higher acetylcysteine dosing. RISK ASSESSMENT AT PRESENTATION: No dose-ranging studies with acetylcysteine were done, and no placebo-controlled studies were performed. Thus, there is uncertainty regarding the optimal dose of acetylcysteine, particularly in patients ingesting very large overdoses of paracetamol. The choice of intervention concentration on the Rumack-Matthew nomogram has important consequences for the proportion of patients treated. The United States National Multicenter Study used a "treatment" line starting at 150 mg/L (992 µmol/L) at 4 hours post overdose, extending to 24 hours with a half-life of 4 hours, now standard there, and subsequently adopted in Australia and New Zealand. In the United Kingdom, the treatment line was initially 200 mg/L (1,323 µmol/L) at 4 hours (the Rumack-Matthew "risk" line). In 2012, the United Kingdom Medicines and Healthcare products Regulatory Agency lowered the treatment line to 100 mg/L (662 µmol/L) at 4 hours for all patients, increasing the number of patients admitted and treated at a high cost. Risk assessment is a key issue for ongoing study, particularly following the development of potential new antidotes that may act in those at greatest risk. The development of biomarkers to assess risk is ongoing but has yet to reach clinical trials. CONCLUSION: Even after 50 years, there are still areas of uncertainty. These include appropriate acetylcysteine doses in patients who ingest different paracetamol doses or multiple (staggered) ingestions, early identification of at-risk patients, and optimal treatment of late presenters.

Extremely Elevated Procalcitonin in a Case of Acetaminophen Overdose and Acute Liver Injury.

We herein report a 46-year-old man who suffered an intentional acetaminophen overdose. Laboratory results revealed leukocytosis and an elevated procalcitonin level (8.48 ng/mL). Computed tomography showed findings suggesting possible colitis. Due to concerns about sepsis in addition to acetaminophen overdose, oral N-acetyl cysteine and piperacillin/tazobactam were started. His procalcitonin levels further increased; however, the patient remained afebrile, and the C-reactive protein levels were normal. Piperacillin/tazobactam was discontinued, and he remained stable without antibiotics. The present case shows that the toxicokinetics of acetaminophen overdose can cause an elevated procalcitonin level. Furthermore, procalcitonin levels alone should not guide the need for antibiotics in such cases.

Morphine Equivalent Total Dosage as Predictor of Adverse Outcomes in Opioid Prescribing.

OBJECTIVE: The objective of this work was to develop a risk prediction model for opioid overdose and opioid use disorder for patients at first opioid prescription and compare the predictive accuracy of morphine equivalent total dosage with the predictive accuracy of daily dosage . DESIGN: Records from patients 18-79 years of age with opioid prescriptions between January 1, 2016, and June 30, 2019, no prior history of adverse outcomes, and no malignant cancer diagnoses were collected from the electronic health record system of a medium-sized central Ohio health care system (n = 219,276). A Cox proportional-hazards model was developed to predict the adverse outcomes of opioid overdose and opioid use disorder from patient sociodemographic, pharmacological, and clinical diagnosis factors. RESULTS: During the study time frame, 573 patients experienced overdoses, and 2,571 patients were diagnosed with opioid use disorder. Morphine equivalent total dosage of opioid prescriptions was identified as a stronger predictor of adverse outcomes (C = 0.797) than morphine equivalent daily dosage (C = 0.792), with the best predictions coming from a model that includes both predictors (C = 0.803). In the model with both daily and total dosage predictors, patients receiving a high total / low daily dosage experienced a higher risk (hazard ratio [HR] = 2.17) than those receiving a low total / high daily dosage (HR = 2.02). Those receiving a high total / high daily dosage experienced the greatest risk of all (HR = 3.09). CONCLUSIONS: These findings demonstrate the value of including morphine equivalent total dosage as a predictor of adverse opioid outcomes and suggest that total dosage may be more strongly correlated with increased risk than daily dosage.

Routine Laboratory Screening for Acetaminophen and Salicylate Ingestion in Preadmission Psychiatric Patients Is Unnecessary.

STUDY OBJECTIVE: Screening preadmission psychiatric patients for acetaminophen or salicylate overdose is unnecessary in the absence of specific clinical concern for medication ingestion. METHODS: This was a multicenter retrospective cohort study of 3 Veteran's Administration emergency departments that medically evaluate patients prior to psychiatric admission. During the 10-year study period, these departments followed screening protocols that required the measurement of acetaminophen and salicylate levels on every patient prior to psychiatric admission. We examined all the acetaminophen and salicylate assays performed to see if any that were sent for screening led to a diagnosis of overdose and/or the administration of antidotal therapy. RESULTS: A total of 33,439 combined acetaminophen and salicylate assays were sent on 10,482 unique patients over approximately 17,000 patient encounters. An estimated 29,000 assays were sent for screening purposes only-87% (95% confidence interval [CI] 85% to 89%) of salicylate assays and 85% (95% CI 83% to 87%) of acetaminophen assays. We identified 43 patients with elevated acetaminophen levels and 11 with elevated salicylate levels. Among these patients, only 6 in total had their levels drawn for screening purposes only, with no history of suspected ingestion; in all but 1 patient, the levels were only slightly above the reference range. None of the patients with elevated levels identified by screening had clinical toxicity or received antidotal therapy. CONCLUSION: Over a 10-year period, 3 Veteran's Administration emergency departments performed psychiatric preadmission screening protocols with acetaminophen and salicylate assays approximately 17,000 times without diagnosing a single case of toxicity. Our results suggest that this practice is unnecessary and wasteful.

Factors associated with seizure development after bupropion overdose: a review of the toxicology investigators consortium.

BACKGROUND: Bupropion is an aminoketone antidepressant. A major concern in bupropion toxicity is seizure activity, which can occur up to 24 h from ingestion. It is difficult to predict which patients will have seizures. The purpose of this study is to identify clinical features associate with seizure after bupropion overdose. METHODS: We searched the Toxicology Investigators Consortium registry for a cases of poisoning by bupropion between January 1, 2014 and January 1, 2017 in patients aged 13-65. Demographic variables and clinical features were compared between patients who did and did not experience a seizure and presented as unadjusted odds ratios (OR). Multivariable logistic regression was used to calculate adjusted odds ratios (aOR) between clinical features and seizures. RESULTS: There were 256 cases of bupropion overdose remaining after inclusion/exclusion criteria were applied. Clinical features associated with seizure were QTc >500 (OR = 3.4, 95% CI: 1.3-8.8, p = 0.012), tachycardia (p > 140) (OR = 1.9, 95% CI: 1-3.561, p = 0.05), and age 13-18 years (2.4, 95% CI: 1.3-4.3, p = 0.005). The mean QTc value for patients experiencing a seizure was 482 ms (N = 95 IQR: 59 ms) versus 454 ms (N = 103, IQR: 43) in patients who did not experience seizure, however, it was not possible to identify a QTc cutoff with sensitivity or specificity to predict seizures. CONCLUSION: Based on our analysis of data from the ToxIC registry, age (13-18), tachycardia (p > 140) and QTc >500 ms are associated with seizures in bupropion overdose; however, a specific QTc value may not be a useful predictor of seizures.

Clinical outcome of massive acetaminophen overdose treated with standard-dose N-acetylcysteine.

BACKGROUND: Recent recognition of "massive" acetaminophen (APAP) overdoses has led to the question of whether standard dosing of N-acetylcysteine (NAC) is adequate to prevent hepatoxicity in these patients. The primary aim of this study was to evaluate the clinical outcome for patients with massive APAP overdose who received standard intravenous NAC dosing of 300 mg/kg over 21 h. METHODS: This was a single-center retrospective cohort study conducted by chart review of APAP overdoses reported to a regional poison center from 1 January 2010 to 31 December 2019. Massive APAP overdose was defined by single, acute overdose resulting in an APAP concentration exceeding 300 mcg/mL at 4 h post-ingestion. Standard univariate statistical analysis was conducted to describe the cohort, and a multivariate logistic model was utilized to calculate adjusted odds ratios for risk of hepatoxicity. RESULTS: 1425 cases of APAP overdose were reviewed. 104 cases met the inclusion criteria of massive APAP overdose. Overall, 79 cases (76%) had no acute liver injury or hepatotoxicity, and 25 (24%) developed hepatoxicity. Nine percent (n = 4) of cases receiving NAC within 8 h developed hepatotoxicity. Crude odds for hepatoxicity was 5.5-fold higher for cases who received NAC after 8 h. CONCLUSIONS: Standard NAC dosing received within 8 h prevented hepatoxicity in 91% (n = 40) of cases in our series of massive APAP overdoses. Additional data is needed to determine the clinical outcomes of massive APAP overdose using current intravenous NAC dosing.

Relatively mild symptoms after chronic overdose with a double-dose encorafenib: a case report.

Encorafenib (Braftovi) is indicated for the treatment of adult patients with unresectable or metastatic melanoma with a BRAF V600 mutation, in combination with binimetinib (Mektovi). According to the product label of encorafenib, there are no specific treatment recommendations in case of an overdose. We report on a 63-year-old man who ingested a double dose (900 mg) of encorafenib for 16 days. He developed overall minor chronic overdose symptoms such as nausea and vomiting grade 1 and muscle pain. Based on the most occurring adverse events of encorafenib, liver values, kidney function parameters and QTc interval were measured. Kidney function parameters were normal, whereas liver values were slightly increased (grade 1) and QTc slightly prolonged. The plasma concentration 3 h after the last dose was 2110 ng/mL. We describe the course of a case with a chronic overdose during 16 days of the double dose of encorafenib as well as the followed approach, which could be taken into account when observing an encorafenib overdose. Providing information in times of Covid-19 is challenging, but remains necessary for good clinical care.

A Case Report of a Severe, Unusually Delayed Anaphylactoid Reaction to Intravenous N-Acetylcysteine During Treatment of Acute Acetaminophen Toxicity in an Adolescent.

INTRODUCTION: Anaphylactoid reactions are well-documented adverse events associated with the intravenous administration of N-acetylcysteine (NAC) in patients with acetaminophen overdose. Most reactions are mild, occurring within the first 1-5 hours of initiation. This report presents the case of an adolescent with a delayed, life-threatening anaphylactoid reaction 24.5 hours after starting NAC, where discontinuing NAC could have resulted in fulminant hepatic failure (FHF) and death. CASE REPORT: A 17-year-old previously healthy female presented with nausea, vomiting, and abdominal pain 10 hours after an acute acetaminophen ingestion. Her 11-hour serum acetaminophen concentration was above the treatment line (149 µg/mL), and she had elevated transaminases (AST = 202 U/L, ALT = 284 U/L). She was treated with intravenous NAC, which was suspended for 3 hours after she developed an apparent life-threatening anaphylactoid reaction with angioedema and respiratory distress 24.5 hours after treatment initiation. Given her high risk of progression to FHF, NAC was resumed at double the previous rate along with scheduled corticosteroids and antihistamines after resolution of her symptoms. Her AST increased to 10,927 U/L, and INR peaked at 3.6, but she had no further anaphylactoid symptoms. She was discharged in her normal state of health after 6 days. DISCUSSION: Discontinuing NAC in this case of severe, delayed anaphylactoid reaction could have resulted in FHF requiring liver transplant. The reason for her reaction is unclear but could be related to patient risk factors or medication error. Guidelines for reinitiation of NAC after development of delayed anaphylactoid reactions are not well-established.  Close observation beyond the first 1-5 hours of NAC administration is warranted.

Delayed peaks of acetaminophen in overdose patients with concomitant abdominal trauma.

OBJECTIVE: To present two cases of delayed acetaminophen absorption in abdominal trauma patients with concomitant acetaminophen overdose. CASES: Case 1. A 25-year-old female arrived to the emergency department with multiple stab wounds. She had ingested an unknown amount of acetaminophen and was then stabbed by her boyfriend in a suicide pact. Initial acetaminophen concentration was 211.7 mcg/mL and the patient was started on N-Acetylcysteine (NAC) therapy. She was found to have injuries and was taken for operative repair. Acetaminophen concentrations were down trending and nearly undetectable until 58 h post-presentation when concentrations began to rise again. CASE 2: A 41-year-old female ingested approximately 500 tablets of acetaminophen prior to jumping from a four-story building in a suicide attempt. She was found to have multiple traumatic injuries as well as an initial acetaminophen concentration of 225 mcg/mL and was started on NAC therapy. The patient underwent multiple interventions to treat her traumatic injuries. Despite receiving no acetaminophen while inpatient, the patient's acetaminophen concentrations peaked a second time on her third hospital day. CONCLUSIONS: In this case series, two patients with abdominal trauma and coexistent massive acetaminophen ingestions were described. Both cases demonstrated a delayed rise in serum acetaminophen concentrations and required extended NAC therapy.

Opioid Overdose Deaths with Buprenorphine Detected in Postmortem Toxicology: a Retrospective Analysis.

BACKGROUND: Buprenorphine is a unique µ-opioid receptor partial agonist with avid receptor binding, nominal euphoric reward, and a ceiling effect on sedation and respiratory depression. Despite a pharmacologic profile that enhances safety, cases of fatal opioid overdose with buprenorphine on postmortem toxicology are reported, but details of these cases in the literature are limited. METHODS: A retrospective review of opioid-involved drug overdose fatalities in Rhode Island (RI) from 2016 to 2018 using the RI Department of Health State Unintentional Drug Overdose Reporting System (SUDORS) database. Deaths with buprenorphine on toxicology testing versus opioid-involved overdose deaths without buprenorphine were compared to assess the type and number of co-exposures. RESULTS: Of 534 opioid-involved deaths, 29 (5.4%) included buprenorphine and/or norbuprenorphine on toxicology. Most frequent co-exposures are as follows: fentanyl (75.9%), norfentanyl (72.4%), cocaine (41.4%), benzoylecgonine (41.4%), cannabinoids (31.0%), ethanol (31.0%), levamisole (31.0%), and free morphine (31.0%). An average number of co-exposures for fatalities with buprenorphine were 9.24 versus 6.68 in those without buprenorphine. In one case buprenorphine was the only drug listed to cause death; all other fatalities with buprenorphine on toxicology reported additional drugs contributing to death. CONCLUSION: Decedents with buprenorphine detected on toxicology testing commonly had documented polysubstance use. Although data are limited, buprenorphine may provide some risk mitigation against full agonist opioid overdose including fentanyl. Further work should explore the use of postmortem concentrations of buprenorphine, norbuprenorphine, and other opioid metabolites to determine the role of buprenorphine in fatal overdose pharmacology.

Unintentional Infiltration of High Dose Epinephrine in an Infant: A Case Report.

Verbal orders in the operating room between the surgeon and circulating nurse are prevalent at many institutions. We present a case in which a communication breakdown involving a verbal order resulted in the patient receiving an excessively high dose of epinephrine via subcuticular infiltration. The overdose was quickly identified by an increase in T-wave amplitude on electrocardiogram (ECG). The hemodynamic changes were treated, and the patient suffered no long-term sequelae. This report emphasizes the need to have strategies in place to prevent medication errors.

The MicroRNA-based Liquid Biopsy Improves Early Assessment of Lethal Acetaminophen Poisoning: A Case Report.

BACKGROUND Acetaminophen overdose is the most common cause of acute liver failure. Nevertheless, new biomarker approaches enabling early prediction of the outcome of the acetaminophen overdose are needed. Recently, using next-generation sequencing analysis of serum from human study participants we uncovered injury-specific signatures of circulating microRNAs (miRNAs) that represented underlying molecular mechanisms of toxicity. This case study is first to show the application of miRNA profiling to assess prognosis of acetaminophen poisoning. CASE REPORT The patient was admitted to the hospital following supra therapeutic acetaminophen ingestion. The patient showed elevated levels of biomarkers of hepatocellular injury alanine aminotransferase, aspartate transaminase, and glutamate dehydrogenase. Even though treatment with N-acetyl cysteine was initiated 24 hours post-ingestion, levels of alanine-aminotransferase and aspartate transaminase peaked at about 40 hours post ingestion of acetaminophen. We analyzed global circulating miRNA levels from 24 consecutive serum samples from this study participant covering the period from admission to time of death. CONCLUSIONS The resulting global miRNA profiles were compared with profiles from study participants with non-lethal acetaminophen poisoning and healthy controls. At the admission, the miRNA profiles of both lethal and non-lethal acetaminophen poisoning showed induction of cellular stress and oxidative damage. Later, the miRNA profiles of the lethal poisoning featured fibrosis and coagulation pathways while profiles of non-lethal cases resembled those of healthy study participants. Although additional confirmatory studies are needed, our case study is first to indicate that global miRNA profiles to be used as liquid biopsies have potential to facilitate the assessment of acetaminophen poisoning.

Elevated procalcitonin levels in patients with acetaminophen intoxication: two case reports: A CARE-compliant article.

RATIONALE: Procalcitonin (PCT) is used as a biomarker for identifying the occurrence of sepsis. Previous studies have reported high levels of PCT with acetaminophen intoxication without evidence of infection. Here, we report two patients with acetaminophen intoxication with high levels of PCT without showing any symptoms of bacterial infection. PATIENT CONCERNS: This case study examined two unrelated patients with acetaminophen intoxication admitted to emergency at different times. The first patient was admitted to the emergency department after ingesting approximately 8000 mg (153.8 mg/kg) of acetaminophen. On admission, C-reactive protein (CRP), glutamic oxaloacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) were normal. PCT and acetaminophen levels were 31.89 ng/mL and below 0.5 µg/mL, respectively. The second patient was admitted to the emergency department 8 h after ingesting ∼23,600 mg (280.6 mg/kg) of acetaminophen. By the second day of admission, GOT and GPT increased to 2508 and 1473 IU/L, respectively. PCT was 45.66 ng/mL with acetaminophen level at 116.9 µg/mL. Both patients were clear of symptoms associated with bacterial infection. DIAGNOSIS: Acetaminophen intoxication. INTERVENTIONS: N-acetylcysteine was given intravenously to both patients for 20 h per protocol. OUTCOMES: Both patients were discharged without complications. LESSONS: Observations suggests that elevated levels of PCT in patients intoxicated with acetaminophen may be associated with involvement of other organs impacted by cytokine stimuli from sterile inflammation resulting from hepatic damage rather than PCT secretion directly caused by hepatic cell damage.

Adducts Post Acetaminophen Overdose Treated with a 12-Hour vs 20-Hour Acetylcysteine Infusion.

INTRODUCTION: Acetaminophen protein adducts in the circulation are a specific biomarker of acetaminophen oxidation, and may be a more sensitive measure of impending hepatic injury following overdose than alanine transaminase (ALT). We performed an exploratory analytical substudy of adducts during a clinical trial (NACSTOP) of abbreviated (12-hour) versus control (20-hour) acetylcysteine to identify any signal of diminished antidotal effectiveness with shortened therapy. METHODS: We measured adducts at 0, 12, and 20 hours from a convenience sample of subjects enrolled in the cluster-controlled NACSTOP trial evaluating a 12-hour ("abbreviated"; 200 mg/kg over 4 hours, 50 mg/kg over 8 hours) vs 20-hour acetylcysteine regimen ("control"; 200 mg/kg over 4 hours, 100 mg/kg over 16 hours). Adducts were assayed using high-performance liquid chromatography/mass spectrometry. RESULTS: Median ALT 20 hours after the initiation of acetylcysteine was 12 U/L (IQR 8,14) in the abbreviated 12-hour regimen group (N = 8), compared with the control group 16 U/L (IQR 11,21; N = 21) (p = 0.46). Adduct concentrations were similarly low in both groups: abbreviated [(0.005 µmol/L, IQR (0,0.14)] and control [(0.005 µmol/L, IQR (0,0.05)] (p = 0.61). CONCLUSIONS: There were minimal to no acetaminophen protein adducts detected. These findings further support discontinuing acetylcysteine when acetaminophen concentrations are low and liver function tests normal after 12 hours of treatment.