Higher Paracetamol Concentrations Research Articles

Intestinal injury in paracetamol overdose (ATOM-8).

Paracetamol, a widely used medication, is known for its delayed hepatotoxicity in cases of overdose. However, the potential for intestinal toxicity resulting from very high paracetamol concentrations during absorption is not well explored. This study aims to investigate the presence of intestinal toxicity and its correlation with observations in early and late paracetamol toxicity. Serial samples of 30 patients with acute paracetamol overdose (>10g or 200mg/kg) were prospectively tested. Markers of enterocyte damage, including plasma intestinal fatty acid binding protein (IFABP) and selected gut-related microRNAs (miR-21, miR-122, miR-194, and miR-215), were analyzed. Sub-analysis was performed on patients presenting with hyperlactatemia defined as a lactate greater than 2mmol/L within 12h post ingestion. In paracetamol overdose patients, median plasma IFABP was significantly elevated compared with healthy controls (720μg/L [interquartile range, IQR, 533-1644] vs 270μg/L [IQR 153-558], P<0.001). Four patients had early hyperlactatemia and had significantly higher median plasma IFABP compared with those without early hyperlactatemia (3028μg/L [IQR 1399-3556] vs 574μg/L [IQR 526-943], P=0.007). Furthermore, two microRNAs (miR-122 and miR-215) were downregulated in early hyperlactatemia (P=0.019 and P=0.006, respectively). Plasma IFABP concentrations correlated with paracetamol concentration (Spearman's r=0.55) and lactate (r=0.60). Paracetamol overdose causes concentration-related intestinal toxicity, and this is a possible explanation for the early hyperlactatemia syndrome. Intestinal toxicity has potential impacts on pharmacokinetics of other agents ingested and on the evolution of hepatotoxicity. Further studies are required to explore the mechanisms and prognostic implications of intestinal toxicity.

An international survey of the treatment of massive paracetamol overdose in 2023

Introduction Changes in the commercialization of nonprescription drugs have made large quantities of paracetamol available to individuals, resulting in larger overdoses than previously observed. Although most patients with paracetamol overdose can be managed with acetylcysteine, patients with a massive overdose may become critically ill earlier and fail standard antidotal therapy. Several strategies are proposed for the management of these patients, including using increased doses of acetylcysteine, extracorporeal removal, and fomepizole. However, the benefits of these strategies remain largely theoretical, with sparse evidence for efficacy in humans. Methods This cross-sectional study surveys international practice patterns of medical toxicology providers regarding the management of a hypothetical patient with a massive paracetamol overdose. Results A total of 342 responses from 31 different nations were obtained during the study period. Sixty-one percent of providers would have increased their acetylcysteine dosing when treating the hypothetical massive overdose. Thirty percent of respondents recommended an indefinite infusion of acetylcysteine at 12.5 mg/kg/hour after the bolus dose, whereas 20 percent recommended following the “Hendrickson” protocol, which advocates for a stepwise increase in acetylcysteine dosing to match high paracetamol concentrations at the 300 mg/L, 400 mg/L, and 600 mg/L lines on the Rumack-Matthew nomogram. Ten percent of respondents stated they would have given “double dose acetylcysteine” but did not specify what that entailed. Forty-seven percent of respondents indicated that they would have given fomepizole, and 28 percent of respondents recommended extracorporeal removal. Discussion Our survey study assessed the approach to a hypothetical patient with a massive paracetamol overdose and demonstrated that, at minimum, most respondents would increase the dose of acetylcysteine. Additionally, almost half would also include fomepizole, and nearly one-third would include extracorporeal removal. Conclusions There is considerable international variation for the treatment of both non-massive and massive paracetamol overdoses. Future research is needed to identify and standardize the most effective treatment for both non-massive and massive paracetamol overdoses.

Updated guidelines for the management of paracetamol poisoning in Australia and New Zealand.

Paracetamol is a common agent taken in deliberate self-poisoning and in accidental overdose in adults and children. Paracetamol poisoning is the commonest cause of severe acute liver injury. Since the publication of the previous guidelines in 2015, several studies have changed practice. A working group of experts in the area, with representation from all Poisons Information Centres of Australia and New Zealand, were brought together to produce an updated evidence-based guidance. The optimal management of most patients with paracetamol overdose is usually straightforward. Patients who present early should be given activated charcoal. Patients at risk of hepatotoxicity should receive intravenous acetylcysteine. The paracetamol nomogram is used to assess the need for treatment in acute immediate release paracetamol ingestions with a known time of ingestion. Cases that require different management include modified release paracetamol overdoses, large or massive overdoses, accidental liquid ingestion in children, and repeated supratherapeutic ingestions. The new guidelines recommend a two-bag acetylcysteine infusion regimen (200mg/kg over 4h, then 100mg/kg over 16h). This has similar efficacy but significantly reduced adverse reactions compared with the previous three-bag regimen. Massive paracetamol overdoses that result in high paracetamol concentrations more than double the nomogram line should be managed with an increased dose of acetylcysteine. All potentially toxic modified release paracetamol ingestions (≥10g or ≥200mg/kg, whichever is less) should receive a full course of acetylcysteine. Patients ingesting ≥30g or ≥500mg/kg should receive increased doses of acetylcysteine.

Massive paracetamol overdose: an observational study of the effect of activated charcoal and increased acetylcysteine dose (ATOM-2)

Context: Paracetamol is commonly taken in overdose, with increasing concerns that those taking “massive” overdoses have higher rates of hepatotoxicity and may require higher doses of acetylcysteine. The objective was to describe the clinical characteristics and outcomes of “massive” (≥ 40 g) paracetamol overdoses.Methods: Patients were identified through the Australian Paracetamol Project, a prospective observational study through Poisons Information Centres in NSW and Queensland, over 3 and 1.5 years, respectively, and retrospectively from three clinical toxicology unit databases (over 2.5 to 20 years). Included were immediate-release paracetamol overdoses ≥ 40 g ingested over ≤ 8 h. Outcomes measured included paracetamol ratio[defined as the ratio of the first paracetamol concentration taken 4–16 h post-ingestion to the standard (150 mg/L at 4 h) nomogram line at that time] and hepatotoxicity (ALT >1000 U/L).Results: Two hundred paracetamol overdoses were analysed, reported median dose ingested was 50 g (interquartile range (IQR): 45–60 g) and median paracetamol ratio 1.9 (IQR: 1.4–2.9, n = 173). One hundred and ninety-three received acetylcysteine at median time of 6.3 h (IQR: 4–9.3 h) post-ingestion. Twenty-eight (14%) developed hepatotoxicity, including six treated within 8 h of ingestion. Activated charcoal was administered to 49(25%), at median of 2 h post-ingestion (IQR:1.5-5 h). Those receiving activated charcoal (within 4 h of ingestion), had significantly lower paracetamol ratio versus those who did not: 1.4 (n = 33, IQR: 1.1–1.6) versus 2.2 (n = 140, IQR: 1.5–3.0) (p < .0001) (paracetamol concentration measured ≥ 1 h after charcoal). Furthermore, they had lower rates of hepatotoxicity [unadjusted OR: 0.12 (95% CI: <0.001–0.91); adjusted for time to acetylcysteine OR: 0.20 (95%CI: 0.002–1.74)].Seventy-nine had a paracetamol ratio ≥2, 43 received an increased dose of acetylcysteine in the first 21 h; most commonly a double dose in the last bag (100 to 200 mg/kg/16 h). Those receiving increased acetylcysteine had a significant decrease risk of hepatotoxicity [OR:0.27 (95% CI: 0.08–0.94)]. The OR remained similar after adjustment for time to acetylcysteine and paracetamol ratio.Conclusion: Massive paracetamol overdose can result in hepatotoxicity despite early treatment. Paracetamol concentrations were markedly reduced in those receiving activated charcoal within 4 h. In those with high paracetamol concentrations, treatment with increased acetylcysteine dose within 21 h was associated with a significant reduction in hepatotoxicity.

In situ optical monitoring of the solution concentration influence on supercritical particle precipitation

We report a novel approach for the measurement of the location of particle formation in the supercritical antisolvent process (SAS). The measurement strategy is based on in situ Raman and elastic light scattering. In the SAS process, paracetamol was used as the solute, ethanol as the solvent and carbon dioxide as the antisolvent. Experiments were performed under miscible conditions for the binary system ethanol and carbon dioxide at 313 K and pressures between 10 MPa and 17.5 MPa. For high paracetamol concentrations in the injected ethanol solution, particles were found to start precipitating after jet breakup in a multi-phase flow. For low paracetamol concentrations, precipitation starts later in a one-phase flow, when the transient interface (phase boundary) between the injected solution and the supercritical carbon dioxide has diminished.

Cytogenetic Evaluation of Paracetamol Effects in Human Lymphocytes Culture

Paracetamol is a common analgesic and antipyretic drug. It has been recognized as one of the most ordinary medications taken in overdoses. We examined the possible genotoxic effects of high paracetamol concentrations expected to occur after overdose. Paracetamol was added to the cultures at the beginning of the cultivation period. Separate cultures for three tested concentrations of paracetamol (50 μg/mL, 100 μg/mL, and 200 μg/mL) were set. Effects of paracetamol were evaluated by micronucleus cytokinesis-block assay, chromosome aberration analysis, and nuclear division index. Results demonstrate that paracetamol concentration of 200 μg/mL expresses certain genotoxic effects in human peripheral blood lymphocytes.

Use of horseradish peroxidase for gene-directed enzyme prodrug therapy with paracetamol.

Gene therapy is a potential method of treating cancer with a greater degree of targeting than conventional therapies. In addition, therapy can be directed towards cells within the tumour population that are traditionally resistant to current treatment schedules. Horseradish peroxidase (HRP) can oxidise paracetamol to N-acetyl-p-benzoquinoneimine via a one-electron pathway. Incubation of human cells expressing HRP with 0.5–10 mM paracetamol reduced clonogenic survival, but had little effect on control cells. A small increase in apoptosis was seen and a decrease in the number of cells undergoing mitosis, consistent with reports in hepatocytes using higher paracetamol concentrations. The cytotoxicity was also seen under conditions of severe hypoxia (catalyst induced anoxia), indicating that the HRP/paracetamol combination may be suitable for hypoxia-targeted gene therapy.

Paracetamol metabolism in the isolated perfused rat liver with further metabolism of a biliary paracetamol conjugate by the small intestine

The isolated, perfused rat liver metabolized paracetamol to glucuronide. sulphate and glutathione conjugates. Sulphate conjugation was the preferred route of metaholism at the drug concentrations studied, but formation of glutathione conjugate became increasingly prominent at higher paracetamol concentrations. Sulphate conjugation was saturated at a paracetamol concentration in the perfusatc of 5 mM. while formation of glucuronide or glutathione conjugates was not yet saturated at 10 mM. The sulphate conjugate was predominantly excreted into the perfusate whereas the excretion pattern for the glucuronide and glutathione conjugates changed with time. Initially, both these conjugates were almost exclusively excreted in the bile, after 90 min perfusion mainly into the perfusate. Preformed paracetamol conjugates were not transferred from perfusate to bile by the isolated perfused liver. Freshly isolated intestinal cells rapidly converted paracetamol- S-glutathione to paracetamol- S-cysteine which was slowly acetylated to the, N-acetylcysteine derivative. Methionine stimulated, and serine-borate inhibited, the breakdown of paracetamol- S-glutathione by intestinal cells, indicating the involvement of γ-glutamyltranspeptidase in the reaction. Biliary paracctamol- S-glutathione was metabolized similarly by the small intestine in situ; the subsequent appearance of the cysteine conjugate in plasma revealed that breakdown of the glutathione conjugate occurred before or during passage through the intestinal wall. Direct absorption of paracetamol- S-cysteine from the intestinal lumen to the portal blood was verified by instillation of this derivative in the intestinal lumen in situ. Analysis of plasma also indicated enterohepatic circulation and reabsorption of biliary paracetamol and paracetamol glucuronide from the intestinal lumen.

Paracetamol metabolism and toxicity in isolated hepatocytes from rat and mouse

Hepatocytes isolated from mouse and rat catalyzed the formation of glucuronide, sulphate, glutathione and cysteine conjugates of paracetamol. These metabolites were separated by high pressure liquid chromatography. 1. Sulphation had higher affinity for paracetamol than glucuronidation in hepatocytes from both mouse and rat, whereas glucuronidation had higher capacity. The maximal rate of glucuronidation was similar in hepatocytes from both species, the rate of sulphation was, however, several-fold less in hepatocytes from mouse. 2. Formation of the glutathione conjugate was directly correlated with loss of intracellular glutathione (GSH). The rate of glutathione conjugate formation increased about three times in rat hepatocytes after phenobarbital treatment. This induced rate was, however, only half of that in hepatocytes from control mouse. In both species the reaction was saturated only at very high paracetamol concentrations. The rate of formation of the cysteine conjugate was very low compared to the other reactions. 3. Only hepatocytes isolated from mouse lost integrity, measured as increased permeability of the cell membranes, upon incubation in the presence of paracetamol.