The effect of activated charcoal on mouse sleep times induced by intravenously administered hypnotics

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.

Influence of activated charcoal on the disposition kinetics of methamphetamine enantiomers in the rat following intravenous dosing

Methamphetamine (MAP) is a central nervous system stimulant that is widely abused by populations of several countries. There is no specific antidote for the treatment of an overdose. Activated charcoal administered orally has been used to enhance the systemic elimination of certain toxic substances via "gastrointestinal dialysis". The results of in vitro studies have shown that MAP can be rapidly adsorbed from solution by activated charcoal. We have evaluated the effect of a single oral dose of activated charcoal on the disposition kinetics of MAP following a short iv infusion. Male Sprague-Dawley rats were given an oral dose of activated charcoal (Actidose-aqua, 1 g/kg) 10 min before a short iv infusion of racemic MAP; whereas the control group was given an equivalent volume of water. Enantiomers of MAP and metabolites in serum and urine were analyzed by an enantiomer-specific method which employed HPLC and detection of a fluorescent derivative. There were no differences in any of the disposition parameters between the two groups. Within each group, the clearance (CLs) of l-MAP was greater than that of d-MAP. However, there were no differences in the steady-state volume of distribution (Vss). The CLs (mL/(min kg)) and Vss (L/kg) values for l- and d-MAP in the control group were (mean +/- SD): 55.8 +/- 20.4, 48.7 +/- 17.9, 2.64 +/- 1.16, and 2.90 +/- 1.36, respectively. The corresponding values in the charcoal-pretreated group were (mean +/- SD): 57.4 +/- 23.4, 51.1 +/- 20.7, 2.79 +/- 1.32, and 2.98 +/- 1.47. These results suggest that oral activated charcoal does not enhance the elimination of MAP from the body.

Correlation of drug pharmacokinetics and effectiveness of multiple-dose activated charcoal therapy

STUDY OBJECTIVE

To evaluate an animal model of multiple-dose activated charcoal (MDAC) therapy and correlate the pharmacokinetic properties of four drugs with the efficacy of MDAC.

DESIGN

Prospective, randomized, controlled, crossover design.

SETTING

A university animal research facility.

PARTICIPANTS

Seven female pigs (15 to 22 kg) with an indwelling central venous line and gastrostomy tube.

INTERVENTIONS

Acetaminophen (30 mg/kg), digoxin (30 micrograms/kg), theophylline (8.9 mg/kg), and valproic acid (18 mg/kg) were simultaneously administered intravenously over 12 minutes. In the experimental arm, 25 g activated charcoal was administered at 0, 2, 4, 6, 12, 18, 24, and 30 hours through the gastric tube. In the control arm, an equal volume of water was given at the same times. Blood specimens were obtained over 36 hours to measure serum drug concentrations.

RESULTS

Each drug exhibited enhanced elimination (P < .01) in the MDAC group except valproic acid. Lower intrinsic clearance was correlated (P < .05) with increased systemic elimination during the charcoal arm. Volume of distribution, half-life, and protein binding were not significantly correlated with charcoal-enhanced systemic drug elimination.

CONCLUSION

The response of a drug to MDAC may be affected by its intrinsic clearance. The restrictive nature of the protein binding of valproic acid may be responsible for its lack of response. Results with the porcine model are consistent with the effects observed in human beings.

Multiple-dose activated charcoal and enhancement of systemic drug clearance: summary of studies in animals and human volunteers

Multiple-dose activated charcoal therapy can enhance the systemic elimination of many drugs. Studies in animals and human volunteers provide a framework for understanding the indications and limitations of multiple-dose activated charcoal therapy. Enterocapillary exsorption creates a compartment for diffusion drugs out of the bloodstream and activated charcoal can augment this process to enhance drug clearance. Once charcoal reaches the intestine, there is a rapid onset of action. Clearance at exsorption sites is limited by blood flow; moreover, the rate of exsorption is related to the dose of charcoal up to a ceiling dose. Drug absorption, distribution, metabolism and elimination dynamically interact with multiple-dose activated charcoal therapy making it difficult to identify a single variable that may predict the success or failure with this therapy. Drug characteristics associated with enhanced systemic clearance with multiple-dose activated charcoal include a low intrinsic clearance, presence in the body for a sufficient time period for charcoal to act, a prolonged distributive phase, non-restrictive protein binding, and a small volume of distribution. Drugs that are unaffected at low doses may respond to multiple doses of activated charcoal when nonlinear kinetics are apparent due to overdose or disease. Although our current understanding is incomplete, multiple-dose activated charcoal therapy will play a role in the future therapy of poisoning patients.

Effect of oral activated charcoal on propranolol pharmacokinetics following intravenous administration to rabbits

The pharmacokinetics of propranolol following intravenous administration (1 mg/kg), with and without treatment with oral activated charcoal, was investigated in rabbits. In charcoal-treated rabbits a significant reduction in propranolol serum concentrations was observed compared to control animals. Charcoal treatment significantly reduced the half-life of elimination (16.6%) and the mean residence time (19%) of propranolol. A 17% increase in the systemic clearance and a 14% decrease in AUC were also noted. Charcoal administration did not significantly alter the volume of distribution (Vc' V(area) and Vss) or the apparent distribution half-life. A two-compartment model adequately described propranolol in control and treated rabbits. The results indicate that administration of oral activated charcoal enhances the systemic elimination of propranolol. This is presumably mediated by interruption of the enterohepatic circulation of propranolol by activated charcoal.

Enhancement of morphine clearance following intravenous administration by oral activated charcoal in rabbits

A single dose of activated charcoal (10 g) significantly reduced the half-life of elimination (1.02 +/- 0.10 and 0.70 +/- 0.04 h for the control and treated groups, respectively) and mean residence time (1.01 +/- 0.12 and 0.76 +/- 0.05 h for the control and treated groups, respectively) of morphine in rabbits. A 40% increase in the systemic clearance (85.73 +/- 7.72 and 122.64 +/- 16.32 mL min-1 kg-1 for the control and treated groups, respectively) and a 30% decrease in AUC (204.38 +/- 22.20 and 140.03 +/- 19.32 micrograms h L-1 in the control and treated groups, respectively) were also noted. Charcoal administration did not significantly alter the volume of distribution (Varea and Vss) or the apparent distribution half-life. A two-compartment model adequately described morphine kinetics in control and treated rabbits; charcoal administration produced a significant increase in the tissue compartment rate constant (K21). This finding indicates that activated charcoal not only enhances the systemic elimination of morphine, but also accelerates the rate of transfer of morphine from the tissue compartment to the central compartment.

Effect of oral activated charcoal on the pharmacokinetics of quinidine and quinine administered intravenously to rabbits

The pharmacokinetics of quinidine and quinine following intravenous administration (10 mg/kg) with and without concurrent treatment with oral activated charcoal was studied in the rabbit. Marked differences were observed in the pharmacokinetic parameters. Compared to quinidine, quinine was characterized by larger volume of distribution (Vd), systemic clearance (Cl) and elimination rate constant (Kel), and smaller half-life of elimination (t1/2), mean residence time (MRT) and area under the curve (AUC). Activated charcoal administered orally (15 g) significantly decreased the serum concentrations of quinidine but not quinine. Furthermore, charcoal treatment significantly enhanced the systemic elimination of quinidine as indicated by the significant increase in Cl and decrease in t1/2, MRT and AUC. By contrast, activated charcoal had no significant effect on the pharmacokinetic parameters of quinine. Differences between quinidine and quinine in respect to the effect of activated charcoal on the systemic elimination of these drugs seem at least, in part, dependent on dispositional factors. The high Cl and Vd of quinine in the rabbit are probably factors that mask the effect of charcoal on the elimination of this drug.

Adsorption of local anesthetics on activated carbon: Freundlich adsorption isotherms

We have shown that adsorbability of local anesthetics onto activated carbon, expressed by the partition coefficients at infinite dilution, correlated well with the pharmacological activity. However, there is no parameter that can singly express the tendency to be adsorbed. Adsorbability is a loosely defined term and its meaning varies with the adsorption model. This study showed that the logarithm of the adsorbed amount of drugs was linearly related to the logarithm of the free drug concentration, in conformity to the Freundlich adsorption isotherms. The slope of the double logarithmic plot is expressed by 1/N in the Freundlich equation and is considered to be inversely related to the drug affinity to the adsorbent. The slope was used to evaluate the tendency to be adsorbed, or "adsorbability" of seven aromatic amine local anesthetics. Phenobarbital was included to compare anionic drugs in contrast to the cationic local anesthetics. The slopes were nearly equal between the cationic and neutral local anesthetics. Apparently, the lower hydrophobicity of the cationic forms is compensated by the electrostatic attraction from the negative charges present on the activated carbon surface. With phenobarbital, the slope value of the anionic form was larger than the neutral form. The lower affinity of the anionic form may be caused by the electrostatic repulsion. The molecular size parameters (i.e., molecular weight, molar refraction, and parachor) showed a linear relationship to the slope values. It may be possible to estimate the affinity-related slope values from these parameters.

Comparative drug exsorption in the perfused rat intestine

The factors affecting drug exsorption into the gastrointestinal tract are uncertain. In this study, the intestinal clearance (CLi) of compounds which vary in their lipophilicity, serum protein binding, molecular weight and ionic charge at physiological pH, has been measured. Male Sprague-Dawley rats with ligated bile ducts were infused with the test compounds through the jugular vein. The small intestine was intubated and perfused with Tyrode solution at 20 mL h-1. The CLi of the compounds investigated (urea, polyethylene glycol, inulin, albumin, dextran, barbituric acid, salicylic acid, thiobarbital, thiopental, thioseconal, theophylline, S-disopyramide and quinidine) was determined under anaesthesia by dividing the rate of a component's appearance rate in the perfusate by its carotid arterial concentration. Serum protein binding of the compounds was determined by equilibrium dialysis. The n-octanol-water partition coefficients of the compounds were measured as indices of lipophilicity. The CLi values of dextran, albumin, inulin, polyethylene glycol and urea were 0.56, 1.03, 4.5, 4.8 and 12.0 mL h-1, respectively. The larger the molecular weight of a compound, the smaller its CLi. The molecular weight is apparently one of the major determinants of CLi. Thiobarbital, thiopental and thioseconal are compounds of similar structure with increasing lipophilicity and serum protein binding. The CLi of thiobarbital, thiopental and thioseconal was proportional to the unbound fraction in serum. The unbound clearance (CLui) of three thiobarbiturates were similar (approximately 11 mL h-1). The unbound fraction of drug in serum appears to be a factor determining their CLi. Barbituric acid and salicylic acid, two acidic compounds, showed a low CLi (less than 1 mL h-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Stereoselective gastrointestinal clearance of disopyramide in rabbits treated with activated charcoal

The ability of activated charcoal to enhance the drug elimination of two enantiomers, R- and S-disopyramide, was compared in rabbits. Orally administered activated charcoal significantly decreased the area under the serum concentration curve of R-disopyramide, whereas the same treatment had no effect on that of S-disopyramide. The difference could be explained by the difference in the hepatic extraction ratio of two enantiomers in rabbits. S-Disopyramide is a drug of high hepatic extraction ratio in rabbits and R-disopyramide is of intermediate hepatic extraction ratio. Equations were derived to illustrate the influence of the hepatic extraction ratio on the apparent gastrointestinal clearance. A higher hepatic extraction ratio decreases the apparent gastrointestinal clearance of a drug. This phenomenon may explain some unsuccessful experiments of gastrointestinal dialysis. When considering the use of activated charcoal to enhance systemic drug elimination, the hepatic extraction ratio of the drug should be included.

Oral activated charcoal in the treatment of intoxications. Role of single and repeated doses

Activated charcoal has an ability to adsorb a wide variety of substances. This property can be applied to prevent the gastrointestinal absorption of various drugs and toxins and to increase their elimination, even after systemic absorption. Single doses of oral activated charcoal effectively prevent the gastrointestinal absorption of most drugs and toxins present in the stomach at the time of charcoal administration. Known exceptions are alcohols, cyanide, and metals such as iron and lithium. In general, activated charcoal is more effective than gastric emptying. However, if the amount of drug or poison ingested is very large or if its affinity to charcoal is poor, the adsorption capacity of activated charcoal can be saturated. In such cases properly performed gastric emptying is likely to be more effective than charcoal alone. Repeated dosing with oral activated charcoal enhances the elimination of many toxicologically significant agents, e.g. aspirin, carbamazepine, dapsone, dextropropoxyphene, cardiac glycosides, meprobamate, phenobarbitone, phenytoin and theophylline. It also accelerates the elimination of many industrial and environmental intoxicants. In acute intoxications 50 to 100g activated charcoal should be administered to adult patients (to children, about 1 g/kg) as soon as possible. The exceptions are patients poisoned with caustic alkalis or acids which will immediately cause local tissue damages. To avoid delays in charcoal administration, activated charcoal should be a part of first-aid kits both at home and at work. The 'blind' administration of charcoal neither prevents later gastric emptying nor does it cause serious adverse effects provided that pulmonary aspiration in obtunded patients is prevented. In severe acute poisonings oral activated charcoal should be administered repeatedly, e.g. 20 to 50g at intervals of 4 to 6 hours, until recovery or until plasma drug concentrations have fallen to non-toxic levels. In addition to increasing the elimination of many drugs and toxins even after their systemic absorption, repeated doses of charcoal also reduce the risk of desorbing from the charcoal-toxin complex as the complex passes through the gastrointestinal tract. Charcoal will not increase the elimination of all substances taken. However, as the drug history in acute intoxications is often unreliable, repeated doses of oral activated charcoal in severe intoxications seem to be justified unless the toxicological laboratory has identified the causative agent as not being prone to adsorption by charcoal. The role of repeated doses of oral activated charcoal in chronic intoxication has not been clearly defined.(ABSTRACT TRUNCATED AT 400 WORDS)

Kinetics of theophylline clearance in gastrointestinal dialysis with charcoal

The pharmacokinetic response of theophylline following the oral administration of activated charcoal was investigated in rabbits. Rabbits were continuously infused with a theophylline solution at a rate of 2.12 mg/h. At the fourth hour of theophylline infusion, 20 g of activated charcoal was administered by intubation to the rabbit (n = 12). The concentration of theophylline in serum gradually decreased after the charcoal treatment. The magnitude of the change in theophylline concentration induced by charcoal varied among animals. By comparing the steady-state theophylline concentration in the control and treated animals, the total body clearance was found to increase from 94.4 +/- 7.5 to 210 +/- 27 mL/h/kg (mean +/- SE). The rate of change of theophylline concentration in serum following charcoal treatment was fitted with a simulation curve by assuming a stepwise increase in clearance immediately following the charcoal treatment. The results indicated that activated charcoal exerted its maximum effect in increasing theophylline clearance immediately after its administration.