Pharmacokinetic modelling of modified acetylcysteine infusion regimens used in the treatment of paracetamol poisoning

Efficacy of a two bag acetylcysteine regimen to treat paracetamol overdose (2NAC study)

BACKGROUND

Previous studies of paracetamol overdose treatment show that a 2-bag, 20-h intravenous (IV) acetylcysteine regimen decreased the incidence of non-allergic anaphylactic reactions compared to the 3-bag, 21 h IV regimen, but have not examined efficacy of the 20-h 2 bag regimen.

METHODS

This was a multi-centre observational study of paracetamol overdose presentations treated with a 2-bag IV acetylcysteine regimen (200 mg/kg over 4 h, 100 mg/kg over 16 h) compared to a 3-bag regimen, performed from 2009 to 2019. Patients were referred from the emergency department to the inpatient toxicology units for continued management. For the primary non-inferiority analysis: subjects had single, acute ingestions, a serum paracetamol-concentration performed 4 to 8-h post-ingestion. The primary outcome was development of acute liver injury (ALI), defined as peak ALT>150 U/L; and > double admission baseline ALT (for presentations within 24 h post-overdose). Secondary outcomes included adverse reactions to acetylcysteine (cutaneous and systemic).

FINDING

Out of 6419 paracetamol overdoses, 2763 received acetylcysteine. For the primary analysis, 1003 received the 2-bag and 783 the 3-bag acetylcysteine regimen. When presentation bloods were performed 4 to 8-h post-overdose, 21 (3.1%) developed ALI with the 2-bag regimen vs 16 (2.9%) with the 3-bag regimen (Difference: 0.2%, 95%CI:-1.6 to 2.2). The incidence of hepatotoxicity was: 1.2% (n = 8) with the two-bag regimen and 1.6% (n = 9) with the three-bag regimen (Difference -0.4%, 95%CI -1.75, 0.91). When presentation bloods were performed 8 to 24-h post-overdose, 70 (21%) developed ALI with the 2-bag regimen vs 46 (23%) with the 3-bag regimen (Difference: -2%, 95%CI -9.12 to 5.36). There were significantly less cutaneous and systemic non-allergic anaphylactic reactions recorded after treatment with the two-bag than the three-bag regimen (1.3% [n = 17] and 7.1% [n = 65], Difference: -5.8%, 95%CI -7.6 to -4.0, p < 0.0001), respectively.

INTERPRETATION

A two-bag intravenous acetylcysteine regimen was found to be non-inferior to the three-bag regimen with regards to efficacy in preventing acute liver injury for early presentations of paracetamol overdose. No important differences were seen for any other presentations. The two-bag regimen also decreased the incidence of both non-allergic anaphylactic reactions and gastrointestinal adverse events from acetylcysteine treatment.

FUNDING

AW is funded by a National Health and Medical Research Council (NHMRC) Early Career Fellowship ID 1159907. GI is funded by a NHMRC Senior Research Fellowship ID 1061041. The NHMRC had no role in the design, writing of this manuscript. The corresponding author (AW) had full access to all the data in the study and final responsibility for the decision to submit the manuscript for publication.

Medicinal Thiols: Current Status and New Perspectives

The thiol (-SH) functional group is found in a number of drug compounds and confers a unique combination of useful properties. Thiol-containing drugs can reduce radicals and other toxic electrophiles, restore cellular thiol pools, and form stable complexes with heavy metals such as lead, arsenic, and copper. Thus, thiols can treat a variety of conditions by serving as radical scavengers, GSH prodrugs, or metal chelators. Many of the compounds discussed here have been in use for decades, yet continued exploration of their properties has yielded new understanding in recent years, which can be used to optimize their clinical application and provide insights into the development of new treatments. The purpose of this narrative review is to highlight the biochemistry of currently used thiol drugs within the context of developments reported in the last five years. More specifically, this review focuses on thiol drugs that represent the standard of care for their associated conditions, including N-acetylcysteine, 2,3-meso-dimercaptosuccinic acid, British anti-Lewisite, D-penicillamine, amifostine, and others. Reports of novel dosing regimens, delivery strategies, and clinical applications for these compounds were examined with an eye toward emerging approaches to address a wide range of medical conditions in the future.

In vitro study of pharmacobezoar formation in simulated acetaminophen overdose

Objectives: There have been few studies of pharmacobezoar formation, but they can be an important contributor to overdose toxicity. Pharmacobezoars may explain the delayed peak or "double hump" pharmacokinetics, which were noted in previous case reports with delayed toxicity of acetaminophen (APAP). We validated the presence of APAP bezoar formation in a controlled modified in vitro environment simulating acute APAP overdose.Methods: This study involved the APAP and control groups (ferrous sulfate and chlorpheniramine). The APAP study group contained three subgroups of APAP with different dosage, i.e., 25 g (50 tabs)/37.5 g (75 tabs)/50 g (100 tabs). The positive control group containing ferrous sulfate, i.e., 15 g (50 tabs), has been reported previously to form pharmacobezoars in overdose. The negative control group containing chlorpheniramine, i.e., 200 mg (50 tabs), has not been reported to form pharmacobezoars in previous case studies. Tablets from each study group were placed into a separate pig stomach. Each stomach contained 28 ml USP standard simulated gastric acid. The stomach was placed in a plastic box filled with water maintaining at 37 °C. Each test group was examined for 4 h in the stomach. The primary outcome was the presence of clump formation. Positive clump formation was defined as tablets sticking together and the ability to maintain shape upon dissecting the pig stomach and lifting with fingers. Tablet clumps would then undergo dissolution testing with subsequent analysis of dissolution profiles.Results: Formation of tablets clumps was confirmed in APAP overdose in the in vitro environment. Clumps were noted to be present in the 37.5 g and 50 g APAP groups, while 25 g APAP was unlikely to form clumps. The dissolution profile of clump demonstrated slower release without reaching plateau at 60 min, as compared to corresponding individual tabs of APAP. f1 and f2 analyses showed the dissolution profile of clump was different compared to that of referenced individual tab.Conclusions: APAP clump formation was confirmed in acute overdose of 37.5 g or more. Dissolution tests revealed delayed and steady release of tablet residue from the clumps, which could explain prolonged or delayed toxicity in large APAP overdose.

The NACSTOP Trial: A Multicenter, Cluster-Controlled Trial of Early Cessation of Acetylcysteine in Acetaminophen Overdose

Historically, intravenous acetylcysteine has been delivered at a fixed dose and duration of 300 mg/kg over 20 to 21 hours to nearly every patient deemed to be at any risk for hepatotoxicity following acetaminophen overdose. We investigated a 12-hour treatment regimen for selected low-risk patients. This was a multicenter, open-label, cluster-controlled trial at six metropolitan emergency departments. We enrolled subjects following single or staggered acetaminophen overdose with normal serum alanine transaminase (ALT) and creatinine on presentation and at 12 hours, and less than 20 mg/L acetaminophen at 12 hours. Patients were allocated to intervention (250 mg/kg over 12-hour) or control (300 mg/kg over 20-hour) regimens by site. The primary outcome was incidence of "hepatic injury" 20 hours following initiation of acetylcysteine treatment, defined as ALT doubling and peak ALT greater than 100 IU/L, indicating the need for further antidotal treatment. Secondary outcomes included incidence of hepatotoxicity (ALT > 1,000 IU/L), peak international normalized ratio (INR), and adverse drug reactions. Of the 449 acetaminophen overdoses receiving acetylcysteine, 100 were recruited to the study. Time to acetylcysteine (median 7 hours [interquartile ratio 6,12] versus 7 hours [6,10]) and initial acetaminophen (124 mg/L [58,171] versus 146 mg/L [66,204]) were similar between intervention and control groups. There was no difference in ALT (18 IU/L [13,22] versus 16 IU/L [13,21]) or INR (1.2 versus 1.2) 20 hours after starting acetylcysteine between groups. No patients developed hepatic injury or hepatotoxicity in either group (odds ratio 1.0 [95% confidence interval 0.02, 50]). No patients represented with liver injury, none died, and 96 of 96 were well at 14-day telephone follow-up. Conclusion: Discontinuing acetylcysteine based on laboratory testing after 12 hours of treatment is feasible and likely safe in selected patients at very low risk of liver injury from acetaminophen overdose.

Reversibly disulfide cross-linked micelles improve the pharmacokinetics and facilitate the targeted, on-demand delivery of doxorubicin in the treatment of B-cell lymphoma

Doxorubicin (DOX) is commonly used to treat human malignancies, and its efficacy can be maximized by limiting the cardiac toxicity when combined with nanoparticles. Here, we reported a unique type of reversibly disulfide cross-linked micellar formulation of DOX (DOX-DCMs) for the targeted therapy of B-cell lymphoma. DOX-DCMs exhibited high drug loading capacity, optimal particle sizes (15-20 nm), outstanding stability in human plasma, and stimuli-responsive drug release profile under reductive conditions. DOX-DCMs significantly improved the pharmacokinetics of DOX, and its elimination half-life (t1/2) and area under curve (AUC) were 5.5 and 12.4 times of that of free DOX, respectively. Biodistribution studies showed that DOX-DCMs were able to preferentially accumulate in the tumor site and significantly reduce the cardiac uptake of DOX. In a xenograft model of human B-cell lymphoma, compared with the equivalent dose of free DOX and non-crosslinked counterpart, DOX-DCMs not only significantly inhibited the tumor growth and prolonged the survival rate, but also remarkably reduced DOX-associated cardiotoxicity. Furthermore, the exogenous administration of N-acetylcysteine (NAC) at 24 h further improved the therapeutic efficacy of DOX-DCMs, which provides a "proof-of-concept" for precise drug delivery on-demand, and may have great translational potential as future cancer nano-therapeutics.

N-acetylcysteine for major mental disorders: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

This systematic review and meta-analysis of randomized controlled trials (RCTs) examined the efficacy and safety of adjunctive N-acetylcysteine (NAC), an antioxidant drug, in treating major depressive disorder (MDD), bipolar disorder, and schizophrenia.

METHODS

The PubMed, Cochrane Library, PsycINFO, CNKI, CBM, and WanFang databases were independently searched and screened by two researchers. Standardized mean differences (SMDs), risk ratios, and their 95% confidence intervals (CIs) were computed.

RESULTS

Six RCTs (n = 701) of NAC for schizophrenia (three RCTs, n = 307), bipolar disorder (two RCTs, n = 125), and MDD (one RCT, n = 269) were identified and analyzed as separate groups. Adjunctive NAC significantly improved total psychopathology (SMD = -0.74, 95% CI: -1.43, -0.06; I² = 84%, P = 0.03) in schizophrenia, but it had no significant effect on depressive and manic symptoms as assessed by the Young Mania Rating Scale in bipolar disorder and only a small effect on major depressive symptoms. Adverse drug reactions to NAC and discontinuation rates between the NAC and control groups were similar across the three disorders.

CONCLUSIONS

Adjunctive NAC appears to be a safe treatment that has efficacy for schizophrenia, but not for bipolar disorder or MDD. Further higher quality RCTs are warranted to determine the role of adjunctive NAC in the treatment of major psychiatric disorders.