In vitro adsorption characteristics of paraquat and diquat with activated carbon varying in particle size

Systematic review on the use of activated charcoal for gastrointestinal decontamination following acute oral overdose

INTRODUCTION

The use of activated charcoal in poisoning remains both a pillar of modern toxicology and a source of debate. Following the publication of the joint position statements on the use of single-dose and multiple-dose activated charcoal by the American Academy of Clinical Toxicology and the European Association of Poison Centres and Clinical Toxicologists, the routine use of activated charcoal declined. Over subsequent years, many new pharmaceuticals became available in modified or alternative-release formulations and additional data on gastric emptying time in poisoning was published, challenging previous assumptions about absorption kinetics. The American Academy of Clinical Toxicology, the European Association of Poison Centres and Clinical Toxicologists and the Asia Pacific Association of Medical Toxicology founded the Clinical Toxicology Recommendations Collaborative to create a framework for evidence-based recommendations for the management of poisoned patients. The activated charcoal workgroup of the Clinical Toxicology Recommendations Collaborative was tasked with reviewing systematically the evidence pertaining to the use of activated charcoal in poisoning in order to update the previous recommendations.

OBJECTIVES

The main objective was: Does oral activated charcoal given to adults or children prevent toxicity or improve clinical outcome and survival of poisoned patients compared to those who do not receive charcoal?  Secondary objectives were to evaluate pharmacokinetic outcomes, the role of cathartics, and adverse events to charcoal administration. This systematic review summarizes the available evidence on the efficacy of activated charcoal.

METHODS

A medical librarian created a systematic search strategy for Medline (Ovid), subsequently translated for Embase (via Ovid), CINAHL (via EBSCO), BIOSIS Previews (via Ovid), Web of Science, Scopus, and the Cochrane Library/DARE. All databases were searched from inception to December 31, 2019. There were no language limitations.  One author screened all citations identified in the search based on predefined inclusion/exclusion criteria. Excluded citations were confirmed by an additional author and remaining articles were obtained in full text and evaluated by at least two authors for inclusion. All authors cross-referenced full-text articles to identify articles missed in the searches. Data from included articles were extracted by the authors on a standardized spreadsheet and two authors used the GRADE methodology to independently assess the quality and risk of bias of each included study.

RESULTS

From 22,950 titles originally identified, the final data set consisted of 296 human studies, 118 animal studies, and 145 in vitro studies. Also included were 71 human and two animal studies that reported adverse events. The quality was judged to have a Low or Very Low GRADE in 469 (83%) of the studies. Ninety studies were judged to be of Moderate or High GRADE. The higher GRADE studies reported on the following drugs: paracetamol (acetaminophen), phenobarbital, carbamazepine, cardiac glycosides (digoxin and oleander), ethanol, iron, salicylates, theophylline, tricyclic antidepressants, and valproate. Data on newer pharmaceuticals not reviewed in the previous American Academy of Clinical Toxicology/European Association of Poison Centres and Clinical Toxicologists statements such as quetiapine, olanzapine, citalopram, and Factor Xa inhibitors were included. No studies on the optimal dosing for either single-dose or multiple-dose activated charcoal were found. In the reviewed clinical data, the time of administration of the first dose of charcoal was beyond one hour in 97% (n = 1006 individuals), beyond two hours in 36% (n = 491 individuals), and beyond 12 h in 4% (n = 43 individuals) whereas the timing of the first dose in controlled studies was within one hour of ingestion in 48% (n = 2359 individuals) and beyond two hours in 36% (n = 484) of individuals.

CONCLUSIONS

This systematic review found heterogenous data. The higher GRADE data was focused on a few select poisonings, while studies that addressed patients with unknown and or mixed ingestions were hampered by low rates of clinically meaningful toxicity or death.  Despite these limitations, they reported a benefit of activated charcoal beyond one hour in many clinical scenarios.

In vitro removal of paraquat and diquat from aqueous media using raw and calcined basil seed

Raw and calcined basil seeds (BS and BS1000, respectively) were evaluated for their ability to remove herbicides such as paraquat and diquat. The physicochemical properties of BS and BS1000 were determined and the effects of contact time and initial concentration on paraquat and diquat adsorption were assessed. After calcination treatment, the number of pores in BS increased, and the specific surface area was increased from 0.265 to 86.902 m² g^-1. The quantity of herbicides adsorbed using BS1000 was greater than that using either BS or medicinal-grade carbon. Additionally, the adsorption quantity increased with the increase in contact time and initial concentration of herbicide. Therefore, BS1000 is a potential resource for the removal of herbicides. Moreover, BS and BS1000 exhibited the capacity for herbicide adsorption in simulated intestinal fluid.

The effects of ω-3 fish oil emulsion-based parenteral nutrition plus combination treatment for acute paraquat poisoning

Objective

To investigate the effects of parenteral nutrition (PN) including ω-3 fish-oil emulsion on nutritional state, inflammatory response, and prognosis in patients with acute paraquat poisoning.

Methods

Patients randomized to receive medium chain triglycerides (MCT)/long chain triglycerides (LCT)-based PN (control group) or MCT/LCT-based PN containing ω-3 fish-oil emulsion (intervention group) were compared for 90-day survival and short-term treatment efficacy.

Results

Tumour necrosis factor-α levels were significantly lower in the intervention group (n = 101) versus controls (n = 73) on treatment days 4 and 7. Intervention group C-reactive protein (CRP) levels were significantly increased on day 4, decreased to baseline (day 1) levels on day 7, and were significantly lower than baseline on day 10. Control group CRP levels were significantly increased on days 4 and 7 versus baseline, and returned to baseline levels on day 10. On day 7, retinol binding protein had recovered to baseline levels in the intervention group only. Intervention group mortality rate (36.6%) was significantly lower than controls (57.5%). ω-3 fish-oil PN was associated with reduced risk of death (hazard ratio 0.52; 95% confidence interval 0.33, 0.82).

Conclusion

In patients with acute paraquat poisoning, MCT/LCT with ω-3 fish-oil emulsion PN plus combination treatment advantageously attenuated the inflammatory response, modified the nutritional state, and was associated with significantly improved 90-day survival versus treatment without ω-3 fish oil.

A bioconjugated design for amino acid-modified mesoporous silicas as effective adsorbents for toxic chemicals

A general synthetic method for functionalization of mesoporous silica with amino acid has been developed. The carboxylic acid functionalized SBA-15 was conjugated with l-phenylalanine (Phe) and l-tryptophan (Trp) to obtain nontoxic amino acid-conjugated functionalized mesoporous silica materials. The materials were used as adsorbents for the removal of the herbicide Paraquat (PQ) and its analog, ethyl viologen dibromide (EVB) from aqueous solutions. In comparison to the commercially available activated carbon adsorbents, the silica-based adsorbents prepared in this study exhibited relatively higher PQ removal efficiency in aqueous solutions at room temperature and pH 7.0. The silica-based adsorbents, pendant with amino acid moieties exhibited greater adsorption capacities toward PQ and EVB than the analogs but without the amino acid moiety, suggesting that there is a benefit for the enhanced π-π interaction between the aromatic groups of the conjugated amino acid moieties and the adsorbate. This bioconjugated method developed here provides a promising new tool to synthesize new materials for detoxification of herbicides in clinical trials.

Paraquat poisonings: mechanisms of lung toxicity, clinical features, and treatment

Paraquat dichloride (methyl viologen; PQ) is an effective and widely used herbicide that has a proven safety record when appropriately applied to eliminate weeds. However, over the last decades, there have been numerous fatalities, mainly caused by accidental or voluntary ingestion. PQ poisoning is an extremely frustrating condition to manage clinically, due to the elevated morbidity and mortality observed so far and due to the lack of effective treatments to be used in humans. PQ mainly accumulates in the lung (pulmonary concentrations can be 6 to 10 times higher than those in the plasma), where it is retained even when blood levels start to decrease. The pulmonary effects can be explained by the participation of the polyamine transport system abundantly expressed in the membrane of alveolar cells type I, II, and Clara cells. Further downstream at the toxicodynamic level, the main molecular mechanism of PQ toxicity is based on redox cycling and intracellular oxidative stress generation. With this review we aimed to collect and describe the most pertinent and significant findings published in established scientific publications since the discovery of PQ, focusing on the most recent developments related to PQ lung toxicity and their relevance to the treatment of human poisonings. Considerable space is also dedicated to techniques for prognosis prediction, since these could allow development of rigorous clinical protocols that may produce comparable data for the evaluation of proposed therapies.

Paraquat adsorption onto clays and organoclays from aqueous solution

Clays were compared with organoclays for the sorption of paraquat from aqueous solution. Sepiolite (S), bentonite (B), and illite (I) were used as clay samples. Organoclays were prepared by the modification of the clays with nonyl- and dodecylammonium chlorides, denoted as NS, DS, NB, DB, NI, and DI, respectively. Specific surface area and pore size distribution of the samples were determined by N2 adsorption-desorption at 77 K using the BET method. X-ray powder diffraction analysis of the samples was used to determine the effects of modifying agents on the layer structure of the clays. In the adsorption experiments, C(m) values increased from 0.038 mmol/g for DS to 0.223 mmol/g for NI. Kd0.3 values ranged from 0.177 for DS to 0.843 for NI. The adsorption data indicated that illite and NI are the most effective adsorbents among these clays and organoclay samples, respectively.