Using 0.45% saline solution and a modified dosing regimen for infusing N-acetylcysteine in children with paracetamol poisoning

Investigating a Novel Two-Bag N-Acetylcysteine Regimen for Acetaminophen Toxicity

BACKGROUND

Acetaminophen toxicity remains one of the most common causes of liver failure and is treated with a course of n-acetylcysteine (NAC). This exceptionally effective medication is traditionally administered using a complicated three-bag protocol that is prone to administration errors.

OBJECTIVE

We aimed to assess whether switching to a novel two-bag protocol (150 mg/kg over 1 h followed by 150 mg/kg over 20 h) reduced administration errors while not increasing liver injury or anaphylactoid reactions.

METHODS

This was a retrospective chart review of hospital encounters for patients with acetaminophen toxicity, comparing outcomes before and after the change from a three-bag protocol to a two-bag protocol at two affiliated institutions. The primary outcome was incidence of medication errors with secondary outcomes including acute liver injury (ALI) and incidence of non-anaphylactoid allergic reactions (NAAR). The study was approved by the health system's Institutional Review Board.

RESULTS

483 encounters were included for analysis (239 in the three-bag and 244 in the two-bag groups). NAAR were identified in 11 patients with no difference seen between groups. Similarly, no differences were seen in ALI. Medication administration errors were observed significantly less often in the two-bag group (OR 0.24) after adjusting for confounders.

CONCLUSION

Transitioning to a novel two-bag NAC regimen decreased administration errors. This adds to the literature that two-bag NAC regimens are not only safe but also may have significant benefits over the traditional NAC protocol.

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.

A review of alternative intravenous acetylcysteine regimens for acetaminophen overdose

INTRODUCTION

Acetylcysteine is the standard treatment for preventing hepatotoxicity caused by acetaminophen overdose. Several novel approaches to the management of acetaminophen overdose have been suggested to improve patient safety by reducing adverse drug reactions and dosing errors. This article reviews these alternative treatment regimens and intends to offer a detailed assessment of the available options to assist providers in managing cases of acetaminophen overdose.

AREAS COVERED

This review article covers observational and experimental studies that assessed the efficacy and safety of alternative intravenous acetylcysteine regimens for acetaminophen overdose. A literature search was conducted using PubMed, ProQuest, and Scopus to identify the studies, which included results through April 2021. The assessment of alternative regimens consists of a discussion on the limitations and benefits, barriers to implementation, and important considerations for each regimen.

EXPERT OPINION

Several alternative regimens have been studied and implemented in various institutions. Many of these dosing regimens have supporting safety data but most lack robust data. A reduction in infusion-related side effects is an important outcome, but established efficacy, local poison center familiarity with the regimen, institutional resources, and patient-specific factors should be equally considered when deciding on implementing and using an alternative dosing strategy.

Evidence for the changing regimens of acetylcysteine

Paracetamol overdose prior to the introduction of acetylcysteine was associated with significant morbidity. Acetylcysteine is now the mainstay of treatment for paracetamol poisoning and has effectively reduced rates of hepatotoxicity and death. The current three-bag intravenous regimen with an initial high loading dose was empirically derived four decades ago and has not changed since. This regimen is associated with a high rate of adverse effects due mainly to the high initial peak acetylcysteine concentration. Furthermore, there are concerns that the acetylcysteine concentration is not adequate for 'massive' overdoses and that the dose and duration may need to be altered. Various novel regimens have been proposed, looking to address these issues. Many of these modified regimens aim to decrease the rate of adverse reactions by slowing the loading dose and thereby decrease the peak concentration. We used a published population pharmacokinetic model of acetylcysteine to simulate these modified regimens. We determined mean peak and 20 h acetylcysteine concentrations and area under the under the plasma concentration-time curve to compare these regimens. Those regimens that resulted in a lower peak acetylcysteine concentration have been shown in studies to have a lower rate of adverse events. However, these studies were too small to show whether they are as effective as the traditional regimen. Further research is still needed to determine the optimum dose and duration of acetylcysteine that results in the fewest side-effects and treatment failures. Indeed, a more patient-tailored approach might be required, whereby the dose and duration are altered depending on the paracetamol dose ingested or paracetamol concentrations.

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.