In vitro adsorption of phenobarbital, chlorpheniramine maleate, and theophylline by four commercially available activated charcoal suspensions

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.

Identification of hypoglycin A binding adsorbents as potential preventive measures in co-grazers of atypical myopathy affected horses

BACKGROUND

Intestinal absorption of hypoglycin A (HGA) and its metabolism are considered major prerequisites for atypical myopathy (AM). The increasing incidence and the high mortality rate of AM urgently necessitate new therapeutic and/or preventative approaches.

OBJECTIVES

To identify a substance for oral administration capable of binding HGA in the intestinal lumen and effectively reducing the intestinal absorption of the toxin.

STUDY DESIGN

Experimental in vitro study.

METHODS

Substances commonly used in equine practice (activated charcoal composition, di-tri-octahedral smectite, mineral oil and activated charcoal) were tested for their binding capacity for HGA using an in vitro incubation method. The substance most effective in binding HGA was subsequently tested for its potential to reduce intestinal HGA absorption. Jejunal tissues of 6 horses were incubated in Ussing chambers to determine mucosal uptake, tissue accumulation, and serosal release of HGA in the presence and absence of the target substance. Potential intestinal metabolism in methylenecyclopropyl acetic acid (MCPA)-conjugates was investigated by analysing their concentrations in samples from the Ussing chambers.

RESULTS

Activated charcoal composition and activated charcoal were identified as potent HGA binding substances with dose and pH dependent binding capacity. There was no evidence of intestinal HGA metabolism.

MAIN LIMITATIONS

Binding capacity of adsorbents was tested in vitro using aqueous solutions, and in vivo factors such as transit time and composition of intestinal content, may affect adsorption capacity after oral administration.

CONCLUSIONS

For the first time, this study identifies substances capable of reducing HGA intestinal absorption. This might have major implications as a preventive measure in cograzers of AM affected horses but also in horses at an early stage of intoxication.

Probing the interactions between chlorpheniramine and 2:1 phyllosilicates

Interactions between chlorpheniramine (CP), an antihistamine drug used to treat allergy, and 2:1 phyllosilicates were studied under batch kinetic and different solution conditions to investigate the effect of charge density of the substrates on CP removal from solution. The CP removal by Na-montmorillonite was instantaneous, with a very large rate constant and a fast rate, reaching a capacity of 0.64 mmol/g, compared to its cation exchange capacity of 0.85 mmol(c)/g. In contrast, CP removal by talc was 10 times lower at 0.06 mmol/g. Stoichiometric desorption of exchangeable cations accompanying CP removal by Na-montmorillonite confirmed cation exchange as the dominant interaction mechanism. Solution pH had a minimal effect on CP removal by Na-montmorillonite until pH 11. On the contrary, a slight increase in CP removal by talc was observed as the solution pH increased, due to increased negative charges on the pH-dependent surfaces of talc. Interactions between CP and Na-montmorillonite occurred on both external and interlayer sites, resulting in a d-spacing expansion from 12.5 Å to 15.2 Å. In contrast, interactions between CP and talc were only limited to the external surfaces. It was the charge density that ultimately controlled the amount of CP removal by 2:1 phyllosilicates. Thus, montmorillonite offers a superior option for the removal of cationic drugs from aqueous solution.

Preparation and evaluation of medicinal carbon oral films

Medicinal carbon (MC) films, which can be taken more easily than other dosage forms, were prepared using sodium carboxymethyl cellulose (CMC), hydroxypropylmethyl cellulose (HPMC) and alginic acid sodium (ALG) as film base materials. Brilliant blue FCF (BB) was used as a model drug. The films containing MC had sufficient strength and disintegration time, but their ability to adsorb BB was clearly inhibited compared to that of MC in powder form. When ALG was used as the film base, the BB adsorption capacity of MC film was approximately 50% of that of MC powder. In an attempt to improve this adsorption ability, two saccharides, sorbitol (SOR) and maltitol (MT), were separately added to MC at a mixing ratio of 1 : 1 by weight. When ALG was the film base, MC films containing SOR or MT showed rapid adsorption profiles and had greatly increased capacities for BB adsorption compared with films containing MC alone. SOR was superior to MT as an additive, though both gave MC-containing films a BB adsorption capacity almost equal to that of MC powder after 24 h, and physical mixtures tended to have better BB adsorption capacities than pre-treatment mixture. In addition, both SOR and MT tended to increase vertical strength of films, but neither additive in either type of mixture had a clear effect on disintegration time. When CMC or HPMC was used as the film base, on the other hand, the addition of SOR or MT caused hardly any improvement in adsorption ability. The above results demonstrate that ALG is useful as a film base material for the preparation of MC films, and that MC films with sufficient strength and adsorption capacities equal to those of MC powders can be produced using a physical mixture of MC and SOR on an ALG base.

In vitro and in vivo evaluation of medicinal carbon granules and tablet on the adsorption of acetaminophen

Medicinal carbon (MC) granules were prepared by wet granulation using maltitol (MT), and the MC tablet was produced by compression of the granules. The physical properties and the in vitro adsorption capacity for AA of the formulations were examined. Further, the effects of MC alone and the granules on gastrointestinal absorption of AA were examined in rats when they were administered intragastrically at 15 or 45 min after the intragastrical administration of AA. AA was rapidly adsorbed by MC, and the maximum adsorption capacity of MC was 0.329g AA per gram MC. The granules and tablet exhibited adequate strength, and the tablet disintegrated rapidly. The granules and tablet showed similar adsorption profiles, but somewhat lower adsorption capacity than MC alone. MC alone and granules administered at 15 min reduced the AUC(0-infinity) significantly against the control (no treatment); however, the suppression effect on the plasma concentration was lower with the granules than with MC alone. Thus, granules and tablet are useful as a compact dosage form of MC; though the reduced adsorption capacity must be taken into account in order to expect efficacy equivalent to that of MC alone.

The Effects of Surface Lactone Hydrolysis and Temperature on the Specific and Nonspecific Interactions Between Phenobarbital and Activated Carbon Surfaces

The effect of hydrolyzing lactone functional groups on the surfaces of different activated carbons upon the specific and nonspecific interactions between phenobarbital and activated carbon surfaces was studied. The effect of temperature on both specific and nonspecific interactions was also studied. The increase in OH groups on the surfaces of activated carbons, as a result of hydrolyzing surface lactone groups, caused an increase in the specific adsorption capacity (K(2)) for phenobarbital without having a significant effect on the hydrophobic bonding capacity (K(HB)). Increasing the temperature at which the adsorption experiment was carried out, on the other hand, resulted in a decrease in K(HB) without having a significant effect on K(2). The decrease in K(HB) per unit temperature increase was the same regardless of the activated carbon. These results are in very good agreement with the modified-Langmuir-like equation (M-LLE).

Medicinal Carbon Tablets for Treatment of Acetaminophen Intoxication: Adsorption Characteristics of Medicinal Carbon Powder and Its Tablets

Adsorption characteristics of medicinal carbon powder (JP 14) for acetaminophen were examined at 37 degrees C using conventional incubation in an attempt to obtain an effective oral dosage form. Hydroxypropyl cellulose (HPC) and maltitol (MT), being able to act as a binding agent, were tested as additives. Tablets of medicinal carbon were produced by the wet granulation method. The rate and extent of adsorption of the medicinal carbon powder were roughly similar in water, JP 14 1st fluid (pH 1.2) and JP 14 2nd fluid (pH 6.8). The relationship between concentrations of free and adsorbed acetaminophen indicated that the adsorption followed the Langmuir mode. The maximal adsorption of acetaminophen in water was 0.219 g per gram medicinal carbon powder, little influenced by the addition of MT, but slightly reduced by the addition of HPC. The tablet prepared using MT as a binding agent displayed a favorable hardness and adequate disintegration time. The tablet showed good adsorption potential for acetaminophen, though the adsorption rate and extent of the tablet were reduced to some extent as compared with powder.

Single‐Dose Activated Charcoal‐Backup and Reassess

Single-dose activated charcoal (SDAC) is frequently administered to poisoned patients. The assumption is that toxin absorption is prevented and that toxicity (as defined by morbidity and mortality) of the poisoning is decreased. Yet there is no evidence that SDAC improves outcome. Risks of this procedure have not been determined. The reported adverse events following SDAC administration are reviewed and risk:benefit ratio for this procedure is discussed.

Effect of ethanol and pH on the adsorption of acetaminophen (paracetamol) to high surface activated charcoal, in vitro studies

BACKGROUND

Paracetamol (acetaminophen) intoxication often in combination with ethanol, is seen commonly in overdose cases. Doses of several grams might be close to the maximum adsorption capacity of the standard treatment dose (50g) of activated charcoal. The aim of this study was to determine the maximum adsorption capacity for paracetamol for two types of high surface-activated charcoal [Carbomix and Norit Ready-To-Use (not yet registered trademark in Denmark) both from Norit Cosmara, Amersfoort, The Netherlands] in simulated in vivo environments: At pH 1.2 (gastric environment), at pH 7.2 (intestinal environment), and with and without 10% ethanol.

METHODS

Activated charcoal, at both gastric or intestinal pHs, and paracetamol were mixed, resulting in activated charcoal-paracetamol ratios from 10:] to 1:1. In trials with ethanol, some of the gastric or intestinal fluid was replaced with an equivalent volume of ethanol, resulting in an ethanol concentration of 10% v/v. After incubation, the concentration of unabsorbed paracetamol was analyzed by high-performance liquid chromatography. The maximum adsorption capacity of paracetamol to activated charcoal was calculated as mg paracetamol adsorbed/g activated charcoal, using Langmuir's isotherm.

RESULTS

Carbomix [95% confidence limits are shown in square brackets]: 623.7 [612.8;634.5] mg paracetamol adsorbed/g activated charcoal (pH 1.2), 626.2 [611.6;640.9] mg paracetamol adsorbed/g activated charcoal (pH 7.2); Norit Ready-To-Use: 693.6 [676.8;710.5] mg paracetamol adsorbed/g activated charcoal (pH 1.2), 722.6 [687.4;757.9] mg paracetamol adsorbed/g activated charcoal (pH 7.2). For experiments with ethanol (10% v/v) the results with Carbomix were 465.7 [449.2;482.2] mg paracetamol adsorbed/g activated charcoal (pH 1.2), 498.6 [481.8;515.6] mg paracetamol adsorbed/g activated charcoal (pH 7.2); with Norit Ready-To-Use: 617.2 [606.6;627.7] mg paracetamol adsorbed/g activated charcoal (pH 1.2), 640.6 [624.9;656.4] mg paracetamol adsorbed/g activated charcoal (pH 7.2).

CONCLUSION

Under conditions simulating immediate treatment with charcoal, a standard dose of 50 g of either of the two tested activated charcoals adsorbed a sufficient amount of paracetamol to be beneficial in the treatment of the majority of overdoses of this drug. For both types of activated charcoal, with or without ethanol, there was no significant difference in the adsorption of paracetamol at pH 1.2 and 7.2. Norit Ready-To-Use had a larger maximum adsorption capacity than Carbomix, and was not as sensitive as Carbomix to environmental changes (pH and ethanol). The presence of 10% ethanol lowered the adsorption capacity of the two tested activated charcoal preparations by an amount that might be clinically relevant in cases of intoxications by high-gram doses.

Activated charcoal as the sole intervention for treatment after childhood poisoning

Childhood poisonings account for approximately two thirds of all human toxic exposures reported annually to the American Association of Poison Control Centers. Activated charcoal (AC) is the mainstay of decontamination in the emergency department setting. This review focuses on six concepts: 1) description of AC and its method of action, 2) evolution of AC in the gastrointestinal decontamination process, 3) prehospital use of AC, 4) superactivated charcoal, 5) multiple-dose AC, and 6) complications of AC administration. The most recent evolving trends in decontamination of the pediatric patient include trends toward earlier decontamination, either in the home or by paramedics in the field. The newer, "super" activated charcoals, with their greater surface area, may improve compliance of oral administration of AC. Finally, guidelines have been set to limit use of multiple-dose activated charcoal regimens to certain pharmaceuticals only, as well as discouraging cathartic use with charcoal dosing.

Adsorption of fluoxetine HCl by activated charcoal

We studied the adsorption of fluoxetine HCl (Prozac) by Norit USP XXIII activated charcoal in vitro, in simulated gastric fluid (USP; pH 1.2), and in simulated intestinal fluid (USP; pH 7.5). The data were fitted to both Langmuir and Freundlich equations. The Langmuir Qm values (maximal adsorption capacities) for pH 1.2 and 7.5 were 0.258 and 0.330 g drug/g charcoal, respectively. These excellent capacities suggest that oral charcoal therapy would be effective for fluoxetine overdose.