A retrospective evaluation of shortened-duration oral N-acetylcysteine for the treatment of acetaminophen poisoning

Acetaminophen toxicity and overdose: current understanding and future directions for NAC dosing regimens

INTRODUCTION

Although N-acetyl-cysteine (NAC) has long been used for the treatment of acetaminophen poisoning/overdose, the optimal NAC dosing regimen for varying patterns or severity of the poisoning/overdose is still unknown.

AREAS COVERED

Relevant literature was searched for in the MEDLINE (from 1964 until August 31^st, 2022), SCOPUS (from 2004 until August 31^st, 2022) and GOOGLE SCHOLAR (from 2004 until August 31^st, 2022) databases, without restriction in terms of publication date. The inclusion criteria were: original clinical studies reporting results, and studies investigating efficacy and safety of NAC dosing regimens in case(s) of overdose or poisoning with acetaminophen.

EXPERT OPINION

For a more effective treatment of acetaminophen poisoning in the future, it will be crucial to advance the technology of measuring acetaminophen, its metabolites and NAC in the serum, preferably with the point-of-care technique, so that in real time it can be continuously assessed whether it is necessary to administer NAC, and further to increase the dose of NAC and extend the duration of its administration, or not.

Acetaminophen Poisoning

Acetaminophen is a common medication taken in deliberate self-poisoning and unintentional overdose. It is the commonest cause of severe acute liver injury in Western countries. The optimal management of most acetaminophen poisonings is usually straightforward. Patients who present early should be offered activated charcoal and those at risk of acute liver injury should receive acetylcysteine. This approach ensures survival in most. The acetaminophen nomogram is used to assess the need for treatment in acute immediate-release overdoses with a known time of ingestion. However, scenarios that require different management pathways include modified-release, large/massive, and repeated supratherapeutic ingestions.

BET 1: In paracetamol overdose, is oral N-acetylcysteine as effective as intravenous N-acetylcysteine?

A short-cut review was carried out to establish whether oral N-acetylcysteine is as effective as intravenous N-acetylcysteine in the management of paracetamol overdose. Seven studies were directly relevant to the question. The author, year and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these papers are tabulated. The clinical bottom line is that oral N-acetylcysteine is a safe alternative in patients for whom the intravenous route is not an option.

Effervescent N-Acetylcysteine Tablets versus Oral Solution N-Acetylcysteine in Fasting Healthy Adults: An Open-Label, Randomized, Single-Dose, Crossover, Relative Bioavailability Study

BACKGROUND

Oral solution N-acetylcysteine (NAC) is an antidote for acetaminophen overdose, but its unpleasant taste and aroma can impede delivery even after the coadministration of antiemetic medications. Flavored effervescent NAC tablets dissolved in water might be a more palatable formulation than oral solution NAC diluted with soft drink.

OBJECTIVES

To evaluate the relative bioavailability of these 2 formulations and assess subjective preferences between them.

METHODS

Thirty healthy adult volunteers (mean [SD] = 35.2 [9.14] years) were enrolled in this open-label, randomized, single-dose, crossover study, with a 7-day washout period. Volunteers were randomized to receive 11 g effervescent test formulation or the reference product under fasting conditions, after which 19 serial blood samples were collected over 48 hours. Total plasma NAC concentrations were evaluated by LC-MS, and pharmacokinetic parameters were calculated. The 2 formulations were considered bioequivalent if the 90% CIs of log-transformed ratios of pharmacokinetic parameters were within the predetermined bioequivalence range (80%-125%) established by the US Food and Drug Administration. Within 15 minutes of dosing, subjects were also asked to rank formulation attributes on a 5-point hedonic scale, with mean group differences analyzed by Wilcoxon signed rank test. Safety-profile assessment included treatment-emergent adverse events, physical examination, chemistry, and hematology parameters.

RESULTS

The concentration-versus-time profiles were similar for the 2 formulations, with mean Cmax of 26.5 μg/mL for effervescent NAC tablets and 28.4 μg/mL for oral solution NAC. The 90% CIs for the pharmacokinetic parameters met the criteria for concluding bioequivalence, and subjects preferred effervescent NAC tablets in terms of taste (P = 0.0247), flavor (P = 0.0082), texture (P = 0.009), and overall likeability (P = 0.0012), but there was no difference for smell (P = 0.0533). All treatment-emergent adverse events were mild, with no differences between the treatment groups.

CONCLUSIONS

Data from this study of a single dose of 11 g oral NAC demonstrated that effervescent NAC tablets and oral solution NAC met the regulatory criteria for bioequivalence in fasting healthy adult subjects. Effervescent NAC tablets appear to be a more palatable alternative for treatment of acetaminophen overdose. ClinicalTrials.gov identifier: NCT02723669. (Curr Ther Res Clin Exp. 2016; 83C:1-7) © 2016 Elsevier HS Journals, Inc.

Acetaminophen-related hepatotoxicity

Acetaminophen (APAP) is the leading worldwide cause of drug overdose and acute liver failure (ALF). Single overdose ingestion and therapeutic misadventure may cause hepatotoxicity. Several factors, such as concomitant alcohol use or abuse, concurrent medications, genetic factors, and nutritional status, can influence the susceptibility and severity of APAP hepatotoxicity. Early manifestations of APAP hepatotoxicity are nonspecific, but require prompt recognition by physicians. Patients with repeated overdose tend to present late, and in such hepatotoxicity may have already evolved. N-acetylcysteine is a very effective antidote when giving within 8 hours, and is also recommended after a presentation of hepatotoxicity and ALF. The prognosis of patients with APAP-induced ALF is better than other causes of ALF. Liver transplantation should be offered to those who are unlikely to survive.

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.

A review of acetaminophen poisoning

Acetaminophen poisoning remains one of the more common drugs taken in overdose with potentially fatal consequences. Early recognition and prompt treatment with N-acetylcysteine can prevent hepatic injury. With acute overdose, the Rumack-Matthew nomogram is a useful tool to assess risk and guide management. Equally common to acute overdose is the repeated use of excessive amounts of acetaminophen. Simultaneous ingestion of several different acetaminophen-containing products may result in excessive dosage. These patients also benefit from N-acetylcysteine. Standard courses of N-acetylcysteine may need to be extended in patients with persistently elevated plasma concentrations of acetaminophen or with signs of hepatic injury.

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.

Toxicology in the ICU: Part 2: specific toxins

This is the second of a three-part series that reviews the generalized care of poisoned patients in the ICU. This article focuses on specific agents grouped into categories, including analgesics, anticoagulants, cardiovascular drugs, dissociative agents, carbon monoxide, cyanide, methemoglobinemia, cholinergic agents, psychoactive medications, sedative-hypnotics, amphetamine-like drugs, toxic alcohols, and withdrawal states. The first article discussed the general approach to the toxicology patient, including laboratory testing; the third article will cover natural toxins.