Comparison of the 20-hour intravenous and 72-hour oral acetylcysteine protocols for the treatment of acute acetaminophen poisoning

Elevated acetaminophen concentration measured after nasal insufflation of Percocet®

BACKGROUND

Prescription opioid products are often formulated with acetaminophen, but the pharmacokinetics of nasally administered acetaminophen are poorly characterized. We report a case of a potentially toxic acetaminophen concentration after nasal insufflation of oxycodone/acetaminophen tablets.

CASE REPORT

A 38-year-old female presented to the emergency department after 2 days of nasally insufflating a total of 50 oxycodone/acetaminophen 5/325 mg tablets. On day 3, she was evaluated for nausea and pharyngitis. She denied oral ingestion of the drug. The initial acetaminophen concentration was 14 μg/mL, although the patient had not insufflated any medication in approximately 24 h. Initial AST and ALT were normal. The patient was treated with a 21-h course of intravenous N-acetylcysteine. On hospital day 2, the measured acetaminophen concentration was < 10 μg/mL and the patient's liver enzymes remained within normal limits.

CONCLUSIONS

The pharmacokinetics of nasally administered acetaminophen have not been well studied, yet there is potential for significant exposure with prescription opioid abuse. Clinicians should be vigilant in evaluating patients for toxicity due to adjunct medications formulated in narcotic pain preparations used by routes other than ingestion.

Direct comparison of 20-hour IV, 36-hour oral, and 72-hour oral acetylcysteine for treatment of acute acetaminophen poisoning

There is no general consensus among clinicians on the superior route or duration of treatment with N-acetylcysteine (NAC) for acute acetaminophen (APAP) poisoning, and head-to-head studies comparing intravenous (IV) and oral NAC have not been done. Recent 20-hour IV NAC protocol failures in the United States prompted some to question its safety. Our objective was to determine if treatment with the 20-hour IV NAC protocol results in clinical outcomes different from the longer 36-hour oral or 72-hour oral NAC protocols in cases of acute APAP poisoning. We performed a retrospective analysis of all consecutive cases of acute APAP overdose where NAC treatment was initiated within 8 hours of ingestion between January 1, 2002, and December 31, 2007. Outcomes were survival, transplant, and death; secondary outcomes were based on King's College Criteria; interrater reliability was calculated with a kappa score. Out of 4642 cases of APAP overdose, 795 met study inclusion criteria: 213 were treated with 20-hour IV protocol, 213 with the 36-hour oral protocol, and 369 with the 72-hour oral protocol. The mean age in these groups was 25 years [95% confidence interval (CI): 22-26], 26 years (95%CI: 23-29), and 27 years (95%CI: 25-28), respectively. The mean 4-hour APAP concentration was 199 μg/mL (95%CI: 188-211), 174 μg/mL (95%CI: 164-184), and 205 μg/mL (95%CI: 195-216), respectively. No cases of transplant or death occurred, and secondary outcomes were rare. When administered within 8 hours of acute APAP poisoning, the 20-hour IV treatment protocol was as effective as the longer 36-hour oral and 72-hour oral treatment protocols. Further study is needed to determine outcome differences between IV and oral NAC when treatment is initiated >8 hours after overdose or in cases of coingestion with other drugs.

Oral and Intravenous Acetylcysteine for Treatment of Acetaminophen Toxicity: A Systematic Review and Meta-analysis

INTRODUCTION

There are few reports summarizing the effectiveness of oral and intravenous (IV) acetylcysteine. We determined the proportion of acetaminophen poisoned patients who develop hepatotoxicity (serum transaminase > 1000 IU/L) when treated with oral and IV acetylcysteine.

METHODS

Studies were double abstracted by trained researchers. We determined the proportions of patients who developed hepatotoxicity for each route using a random effects model. Studies were further stratified by early and late treatment.

RESULTS

We screened 4,416 abstracts; 16 articles, including 5,164 patients, were included in the meta-analysis. The overall rate of hepatotoxicity for the oral and IV routes were 12.6% and 13.2%, respectively. Treatment delays are associated with a higher rate of hepatotoxicity.

CONCLUSION

Studies report similar rates of hepatotoxicity for oral and IV acetylcysteine, but direct comparisons are lacking. While it is difficult to disentangle the effects of dose and duration from route, our findings suggest that the rates of hepatotoxicity are similar for oral and IV administration.

Therapeutic effect of liposomal-N-acetylcysteine against acetaminophen-induced hepatotoxicity

BACKGROUND

Acetaminophen (APAP) is an antipyretic analgesic drug that when taken in overdose causes depletion of glutathione (GSH) and hepatotoxicity. N-acetylcysteine (NAC) is the antidote of choice for the treatment of APAP toxicity; however, due to its short-half-life repeated dosing of NAC is required.

PURPOSE

To determine whether a NAC-loaded liposomal formulation (Lipo-NAC) is more effective than the conventional NAC in protecting against acute APAP-induced hepatotoxicity.

METHODS

Male Sprague-Dawley rats were challenged with an intragastric dose of APAP (850 mg/kg b.wt.); 4 h later, animals were administered saline, NAC, Lipo-NAC or empty liposomes and sacrificed 24 h post-APAP treatment.

RESULTS

APAP administration resulted in hepatic injury as evidenced by increases in plasma bilirubin, alanine (AST) and aspartate (ALT) aminotransferase levels and tissue levels of lipid peroxidation and myeloperoxidase as well as decreases in hepatic levels of reduced GSH, GSH peroxidase and GSH reductase. Treatment of animals with Lipo-NAC was significantly more effective than free NAC in reducing APAP-induced hepatotoxicity. Histological evaluation showed that APAP caused periacinar hepatocellular apoptosis and/or necrosis of hepatocytes around the terminal hepatic venules which was reduced by NAC treatment, the degree of reduction being greater for Lipo-NAC.

CONCLUSION

These data suggest that administration of Lipo-NAC ameliorated the APAP-induced hepatotoxicity.

Children intoxications: what is abuse and what is not abuse

The curiosity and the natural tendency to explore the environment put young children at an increased risk of poisoning over older children and adults. Poisonings are a significant area of concern from 1 year of age and progressively contribute more to overall rates of morbidity and mortality until children reach adulthood. Particularly, the abuse of children by poisoning is also highly common with thousands of fatalities. A practical strategy is presented that aims to alert health, forensic, and law enforcement professionals to this problem and to demystify the preconception that it is a rare form of abuse or neglect. Compounds that are foreign to a living organism (xenobiotics) and those present within body (endobiotics), mainly involved in children intoxications and contextual examples related to exposure are also reviewed. Particular concern is given to concepts in the field of children poisoning. The described history and the clinical and toxicological evaluation are discussed, and harmonized protocols regarding correct procedures for sample collection to forensic toxicological analysis are proposed. Since children are particularly vulnerable to the toxic effects of high doses of xenobiotics and endobiotics, special consideration on the preparation of the environment that surrounds children in order minimize all possible risks will be also considered.

The proper use of acetaminophen

Acetaminophen (N-acetyl-p-aminophenol, paracetamol [APAP])-induced acute liver failure is the most common cause of acute liver failure in adults. In children, APAP accounts for 25% of all cases of acute liver failure. The high mortality rate associated with this preventable condition makes it vital that paediatricians are aware of the potential adverse effects associated with this widely used drug. While APAP is generally considered to be safe when used as directed, its inclusion in multiple over-the-counter medications, as well as in prescription drugs, mandates that physicians promote and educate the general public about the proper use of acetaminophen in children.

Modeling drug- and chemical-induced hepatotoxicity with systems biology approaches

We provide an overview of computational systems biology approaches as applied to the study of chemical- and drug-induced toxicity. The concept of “toxicity pathways” is described in the context of the 2007 US National Academies of Science report, “Toxicity testing in the 21st Century: A Vision and A Strategy.” Pathway mapping and modeling based on network biology concepts are a key component of the vision laid out in this report for a more biologically based analysis of dose-response behavior and the safety of chemicals and drugs. We focus on toxicity of the liver (hepatotoxicity) – a complex phenotypic response with contributions from a number of different cell types and biological processes. We describe three case studies of complementary multi-scale computational modeling approaches to understand perturbation of toxicity pathways in the human liver as a result of exposure to environmental contaminants and specific drugs. One approach involves development of a spatial, multicellular “virtual tissue” model of the liver lobule that combines molecular circuits in individual hepatocytes with cell–cell interactions and blood-mediated transport of toxicants through hepatic sinusoids, to enable quantitative, mechanistic prediction of hepatic dose-response for activation of the aryl hydrocarbon receptor toxicity pathway. Simultaneously, methods are being developing to extract quantitative maps of intracellular signaling and transcriptional regulatory networks perturbed by environmental contaminants, using a combination of gene expression and genome-wide protein-DNA interaction data. A predictive physiological model (DILIsym™) to understand drug-induced liver injury (DILI), the most common adverse event leading to termination of clinical development programs and regulatory actions on drugs, is also described. The model initially focuses on reactive metabolite-induced DILI in response to administration of acetaminophen, and spans multiple biological scales.

Novel acetylcysteine regimens for treatment of paracetamol overdose

Paracetamol (acetaminophen) overdose remains the leading cause of death or transplantation due to acute liver failure in many parts of the world. Acetylcysteine has long been recognized as an effective antidote, via oral or intravenous administration, minimizing the risk and severity of acute liver injury if administered sufficiently early after a paracetamol overdose. Despite this, its mechanisms of action remain obscure, and there is uncertainty regarding the optimal dose and duration of treatment. The intravenous infusion protocol was originally developed as a three-step loading regimen; it causes very high early peak plasma concentrations of acetylcysteine whereas the later maintenance infusion is associated with much lower concentrations. This pharmacokinetic profile is associated with two particular concerns: a high rate of occurrence of adverse effects that occur after the initial loading infusion, and the possibility that the maintenance phase of treatment might deliver too low a dose of acetylcysteine for optimum protection against liver injury. Recently described novel administration regimens offer different rates of intravenous acetylcysteine administration in both the loading and maintenance phases. These alternative regimens appear to be well tolerated in small patient groups, but too few clinical data are available to evaluate their comparative efficacy in preventing paracetamol-induced liver injury.

An analysis of N-acetylcysteine treatment for acetaminophen overdose using a systems model of drug-induced liver injury

N-acetylcysteine (NAC) is the treatment of choice for acetaminophen poisoning; standard 72-h oral or 21-h intravenous protocols are most frequently used. There is controversy regarding which protocol is optimal and whether the full treatment course is always necessary. It would be challenging to address these questions in a clinical trial. We used DILIsym, a mechanistic simulation of drug-induced liver injury, to investigate optimal NAC treatment after a single acetaminophen overdose for an average patient and a sample population (n = 957). For patients presenting within 24 h of ingestion, we found that the oral NAC protocol preserves more hepatocytes than the 21-h intravenous protocol. In various modeled scenarios, we found that the 21-h NAC infusion is often too short, whereas the full 72-h oral course is often unnecessary. We found that there is generally a good correlation between the time taken to reach peak serum alanine aminotransferase (ALT) and the time taken to clear N-acetyl-p-benzoquinone imine (NAPQI) from the liver. We also found that the most frequently used treatment nomograms underestimate the risk for patients presenting within 8 h of overdose ingestion. V(max) for acetaminophen bioactivation to NAPQI was the most important variable in the model in determining interpatient differences in susceptibility. In conclusion, DILIsym predicts that the oral NAC treatment protocol, or an intravenous protocol with identical dosing, is superior to the 21-h intravenous protocol and ALT is the optimal available biomarker for discontinuation of the therapy. The modeling also suggests that modification of the current treatment nomograms should be considered.

Antidotes for toxicological emergencies: a practical review

PURPOSE

Appropriate therapies for commonly encountered poisonings, medication overdoses, and other toxicological emergencies are reviewed, with discussion of pharmacists' role in ensuring their ready availability and proper use.

SUMMARY

Poisoning is the second leading cause of injury-related morbidity and mortality in the United States, with more than 2.4 million toxic exposures reported each year. Recently published national consensus guidelines recommend that hospitals providing emergency care routinely stock 24 antidotes for a wide range of toxicities, including toxic-alcohol poisoning, exposure to cyanide and other industrial agents, and intentional or unintentional overdoses of prescription medications (e.g., calcium-channel blockers, β-blockers, digoxin, isoniazid). Pharmacists can help reduce morbidity and mortality due to poisonings and overdoses by (1) recognizing the signs and symptoms of various types of toxic exposure, (2) guiding emergency room staff on the appropriate use of antidotes and supportive therapies, (3) helping to ensure appropriate monitoring of patients for antidote response and adverse effects, and (4) managing the procurement and stocking of antidotes to ensure their timely availability.

CONCLUSION

Pharmacists can play a key role in reducing poisoning and overdose injuries and deaths by assisting in the early recognition of toxic exposures and guiding emergency personnel on the proper storage, selection, and use of antidotal therapies.

Acetaminophen and acetylcysteine dose and duration: past, present and future

Acetylcysteine has been utilized successfully in the treatment of acetaminophen overdose since the 1970s. Although prospective trials as to efficacy and safety of acetylcysteine were conducted, there were no randomized controlled trials. This commentary addresses the reasons for this, and the background to choice of dose of acetylcysteine utilized in the oral and IV dosing regimens. Nomograms to predict possible hepatotoxicity based upon time of ingestion of acetaminophen were developed from a relatively arbitrary definition of toxicity as an aspartate aminotransferase/alanine aminotransferase (ALT/AST) greater than 1000 IU/L. While these have proved generally useful, patients still continue to develop hepatic damage after acetaminophen overdose, particularly if they present late after ingestion. The optimum management of these patients remains unclear, and one area of uncertainty is the dose and duration of acetylcysteine in various circumstances. This article discusses the issues that need to be elucidated to better target changes in acetylcysteine dose. The potential for measurements of other markers to improve treatment selection is the subject of further research.

The clinical management of acetaminophen poisoning in a community hospital system: factors associated with hospital length of stay

Acetaminophen (APAP) overdose is the most common pharmaceutical poisoning. The objective of this study was to examine the management of patients admitted for treatment of APAP overdose. Factors impacting hospital length of stay (LOS) were of particular interest. This was a retrospective cohort study of patients admitted to Kaiser Permanente Northern California hospitals for APAP overdose from July 2003 through December 2007. Medical records were abstracted for patient demographic data, key factors of overdose, California Poison Control System (CPCS) contact, data regarding hospital course, transfer for liver transplantation, and death. Four hundred thirty-five patients were included. The mean hospital LOS was 66.5 h (95% CI 62.1, 71.0). Four patients (0.9%) died. Eight patients (1.8%) were transferred for liver transplantation, but all of these patients later recovered without transplant. Of 289 cases eligible for placement on the Rumack-Matthew nomogram (acute ingestion with known time of ingestion <24 h and normal liver enzymes), 161 (55.7%) had APAP levels above the "200" line and 77 (26.6%) fell below the "150" line. CPCS was contacted in 295 cases (67.8%). Mean LOS in cases with CPCS consultation was 61.9 h (95% CI 57.2, 66.5 h) versus 76.3 h (95% CI 66.6, 86.0 h) in those without. LOS in cases treated with IV NAC was 67.1 h (95% CI 57.7, 76.5 h) versus 66.4 h (95% CI 61.2, 71.5 h) in cases treated with oral NAC. Many patients admitted for APAP overdose had serum APAP levels below the minimum toxicity level. Use of IV NAC did not impact hospital LOS. CPCS consultation appeared to decrease mean hospital LOS.

Toxicology today: what you need to know now

Clinicians are frequently confronted with toxicological emergencies and challenged with the task of correctly identifying the possible agents involved and providing appropriate treatments. In this review article, we describe the epidemiology of overdoses, provide a practical approach to the recognition and diagnosis of classic toxidromes, and discuss the initial management strategies that should be considered in all overdoses. In addition, we evaluate some of the most common agents involved in poisonings and present their respective treatments. Recognition of toxidromes with knowledge of indications for antidotes and their limitations for treating overdoses is crucial for the acute care of poisoned patients.

Drugs and pharmaceuticals: management of intoxication and antidotes

The treatment of patients poisoned with drugs and pharmaceuticals can be quite challenging. Diverse exposure circumstances, varied clinical presentations, unique patient-specific factors, and inconsistent diagnostic and therapeutic infrastructure support, coupled with relatively few definitive antidotes, may complicate evaluation and management. The historical approach to poisoned patients (patient arousal, toxin elimination, and toxin identification) has given way to rigorous attention to the fundamental aspects of basic life support--airway management, oxygenation and ventilation, circulatory competence, thermoregulation, and substrate availability. Selected patients may benefit from methods to alter toxin pharmacokinetics to minimize systemic, target organ, or tissue compartment exposure (either by decreasing absorption or increasing elimination). These may include syrup of ipecac, orogastric lavage, activated single- or multi-dose charcoal, whole bowel irrigation, endoscopy and surgery, urinary alkalinization, saline diuresis, or extracorporeal methods (hemodialysis, charcoal hemoperfusion, continuous venovenous hemofiltration, and exchange transfusion). Pharmaceutical adjuncts and antidotes may be useful in toxicant-induced hyperthermias. In the context of analgesic, anti-inflammatory, anticholinergic, anticonvulsant, antihyperglycemic, antimicrobial, antineoplastic, cardiovascular, opioid, or sedative-hypnotic agents overdose, N-acetylcysteine, physostigmine, L-carnitine, dextrose, octreotide, pyridoxine, dexrazoxane, leucovorin, glucarpidase, atropine, calcium, digoxin-specific antibody fragments, glucagon, high-dose insulin euglycemia therapy, lipid emulsion, magnesium, sodium bicarbonate, naloxone, and flumazenil are specifically reviewed. In summary, patients generally benefit from aggressive support of vital functions, careful history and physical examination, specific laboratory analyses, a thoughtful consideration of the risks and benefits of decontamination and enhanced elimination, and the use of specific antidotes where warranted. Data supporting antidotes effectiveness vary considerably. Clinicians are encouraged to utilize consultation with regional poison centers or those with toxicology training to assist with diagnosis, management, and administration of antidotes, particularly in unfamiliar cases.