Studies on the binding properties of acidic, basic and neutral drugs to anion and cation exchange resins and charcoal in vitro

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-vivo binding of lithium using the cation exchange resin sodium polystyrene sulfonate

The purpose of this study was to determine if the exchange resin sodium polystyrene sulfonate increases the clearance of lithium in a healthy volunteer. A single healthy volunteer received 900 mg lithium for each of three study phases. A sodium polystyrene sulfonate dose of either 0, 20, or 40 grams was administered one half hour after each lithium dose to assess the effect on lithium clearance. Multiple blood samples were obtained for serum lithium concentrations over a 36- to 48-hour time period. Pharmacokinetic parameter estimates were calculated and compared. Sodium polystyrene sulfonate was found to increase the clearance of lithium in a single volunteer. Sodium polystyrene sulfonate may be useful in the treatment of lithium intoxication by increasing the clearance of lithium.

In vitro binding of lithium using the cation exchange resin sodium polystyrene sulfonate

Sodium polystyrene sulfonate, a cation exchange resin, should be useful in the treatment of lithium overdosage. This in vitro study was conducted to assess the ability of sodium polystyrene sulfonate to bind lithium, effects of pH on binding, binding efficacy in comparison to charcoal, and affinity for lithium versus potassium. Stock solutions of lithium were added to fixed amounts of sodium polystyrene sulfonate and charcoal. Lithium and potassium concentrations in supernatant were measured by flame photometry. Increasing concentrations of sodium polystyrene sulfonate bound more lithium. Changes in pH had little effect on lithium binding. Lithium is bound to sodium polystyrene sulfonate more readily than to charcoal. Potassium is preferentially bound to sodium polystyrene sulfonate over lithium. Sodium polystyrene sulfonate may provide a useful therapeutic modality in the treatment of lithium overdosage.

Gastrointestinal dialysis of digoxin using cholestyramine

The pharmacokinetic parameters of digoxin given intravenously (0.075 mg/kg) alone and following treatment with oral cholestyramine (8 gm in 50 ml water) were studied in rabbits. Pretreatment with cholestyramine produced a significant decrease in the serum concentration of digoxin and significantly enhances its systemic clearance as indicated by a statistically significant decrease in the area under the concentration-time curve (AUC), half time of elimination (t 1/2), and mean residence time (MRT). These findings indicate that the idea of gastrointestinal dialysis, known with activated charcoal, could be extended to ion-exchange resins that could be a potentially useful adjunctive measure in the management of drug overdose especially with commonly used drugs with a low therapeutic index like digoxin.

Does ethanol modify antidotal efficacy of oral activated charcoal studies in vitro and in experimental animals

The effect of ethanol on the adsorption of strychnine to activated charcoal was studied in vitro at pH 1.2 and 7.0. At high charcoal-drug ratios the adsorption of strychnine was significantly (p less than 0.001) more complete at neutral pH than at pH 1.2. At these ratios ethanol 10% increased (p less than 0.001) the unadsorbed fractions at both pHs. The acute toxicity of oral strychnine in mice was not influenced by ethanol. Activated charcoal (1000 mg/kg) mixed with strychnine prior to the administration increased its LD50 by 410 fold. When ethanol was administered with charcoal and strychnine, the increase in the LD50 was only 220 fold which is significantly (p less than 0.05) less than without ethanol. Accordingly, the concomitant ingestion of ethanol in drug intoxications may slightly impair the antidotal efficacy of oral activated charcoal. Despite this potential reduction of the antidotal efficacy of charcoal in some extreme situations, there should be no hesitation in administering activated charcoal in acute intoxications since it in any case very effectively inhibits the absorption of most drugs.

Simultaneous identification and quantitation of diphenhydramine and methaqualone

Methods for the simulataneous identification and quantitation of diphenhydramine and methaqualone in urine have been investigated. Suitable thin-layer and gas chromatographic techniques have been developed. The extraction techniques were evaluated by extracting human urine after the ingestion of therapeutic dosages of the two drugs. A charcoal cartridge technique proved to be superior to direct solvent extraction. Although enzyme hydrolysis gave slightly better recoveries than the charcoal cartridge technique, it is a time-consuming procedure.