Effect of activated charcoal on the pharmacokinetics of pholcodine, with special reference to delayed charcoal ingestion

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.

Novel method to estimate the appropriate dosing interval for activated charcoal to avoid interaction with other drugs

PURPOSE

Activated charcoal is known to adsorb a variety of drugs concomitantly administered and reduce their intestinal absorption, and separating the dosing is considered a practical approach to avoid this drug interaction. The aim of the present study was to develop and validate a simple method to estimate the sufficient dosing interval to avoid drug interaction using the pharmacokinetic profile of the subject drugs administered alone and the amplitude of interaction upon simultaneous administration with activated charcoal.

METHODS

For each subject drug, the pharmacokinetic profile and the amplitude of interaction, as assessed by AUCR (the ratio of area under the plasma concentration-time curve (AUC) in the presence of activated charcoal to that in its absence), were collected from previous reports. The AUCR value was estimated based on the compartment model under the assumption that the subject drug in the first gastrointestinal compartment is immediately adsorbed to a certain extent upon the administration of activated charcoal. The estimated AUCR (AUCR_e) for each drug with certain dosing interval was compared with the respective AUCR value reported previously (AUCR_obs).

RESULTS

Among twenty concentration profiles for 14 subject drugs obtained from previous reports, 15 AUCR_e values fell in the range of 80-120% of the respective AUCR_obs values.

CONCLUSION

The developed method enabled estimation of the amplitude of DDI by activated charcoal administered in a certain dosing interval, whereas overestimation of AUCR_e was observed for drugs that undergo extensive enterohepatic circulation.

The feasibility of administration of activated charcoal with respect to current practice guidelines in emergency department patients

OBJECTIVE

The American Academy of Clinical Toxicology, European Association of Poisons Centres, and Clinical Toxicologists recommend administration of activated charcoal (AC) within one-hour of an acute toxic ingestion [1]. Our poison control center periodically and upon request faxes an abbreviated protocol to hospital emergency departments, reminding physicians of these current AC recommendations. This study was conducted to describe how often patients present within the one-hour time frame and how often the guidelines in the above position statement are being followed.

METHODS

Following a brief training of systematic chart review, reviewers blinded to the purpose of the study completed a standardized data collection sheet. Three years after publication of these consensus statements, a period of 3 consecutive years of poison center patient encounters were reviewed. Recorded data included age, outcomes, and time to administration of charcoal.

RESULTS

Approximately 150,000 reported toxic exposures were reviewed, of which 16,914 patients of acute ingestions presented to a health care facility. The mean age of the group that presented was 25 years [range 1 month-87 years]. A total of 2,700 (16%) patients that presented were within 60 minutes of an acute overdose and all were administered AC in accordance with the recommended guidelines. Interestingly, pre-hospital personnel administered AC within 60 minutes to 762 (28% of 2,700) patients. Correspondingly, 14,214 (84%) patients presented more than 60 minutes after an acute overdose. Of this latter group AC was withheld in 341 (2.4% of 14,214) patients, and 13,873 (97.6% of 14,214) patients received charcoal despite having arrived more than 60 minutes after ingestion. The mean time to the first administration of AC in this latter group was 225 minutes [range of 61-2160 minutes] following ingestion.

CONCLUSIONS

Only a small percentage of patients treated for an acute overdose (16%) present within 60 minutes and are given charcoal according to the current guidelines. A large subset of these patients (28%) is given AC in a pre-hospital setting. Few patients presenting to a health care provider after an acute toxic ingestion are treated in accordance with the current recommendations for activated charcoal.

Adsorptive capacity of activated charcoal for rifampicin with and without sodium chloride and sodium citrate

The effects of two saline cathartics (sodium chloride and sodium citrate) on the adsorptive capacity of activated charcoal (AC) for rifampicin were studied. Solutions of rifampicin alone and rifampicin with 7.5 mg/ml cathartic solution were vortex-mixed for 30 s with different quantities of AC. These were incubated for 30 min at 37 degrees C and analyzed for free rifampicin spectrophotometrically at 320 nm. The addition of sodium citrate significantly increased (p<0.05) the adsorptive capacity of AC for rifampicin with a resulting decrease in B-50 values at both the therapeutic and simulated toxic doses. Sodium chloride addition reduced the binding of rifampicin to AC at the toxic doses. The adsorption of rifampicin to activated charcoal, both alone and with the two saline cathartics, obeyed quantity-dependent kinetics. AC may be co-administered with sodium citrate in the management of rifampicin overdose.

Effectiveness of delayed activated charcoal administration in simulated paracetamol (acetaminophen) overdose

AIMS

Oral activated charcoal is used to treat drug overdose and is effective at reducing drug absorption when administered within 1 h of drug ingestion. There are fewer data on efficacy when the delay is longer, as is the case in most drug overdoses. This study investigated the efficacy of activated charcoal at preventing paracetamol (acetaminophen) absorption after simulated overdose when administration was delayed between 1 and 4 h.

METHODS

An open randomized-order four-way crossover study was performed in healthy volunteers comparing the effect of activated charcoal 50 g on the absorption of 3 g paracetamol tablets when administered after an interval of 1, 2 or 4 h or not at all. Plasma paracetamol concentrations were measured over 9 h after paracetamol ingestion using h.p.l.c. and areas under the curve between 4 and 9 h (AUC(4,9 h)) calculated as a measure of paracetamol absorption.

RESULTS

Activated charcoal significantly reduced paracetamol AUC(4,9 h) when administered after 1 h (mean reduction 56%; 95% Confidence intervals 34, 78; P<0.002) or 2 h (22%; 6, 39; P<0.03) but not after 4 h (8%; -8, 24). When administered after 1 h activated charcoal reduced individual plasma paracetamol concentrations significantly at all times between 4 and 9 h after paracetamol administration. Administration at 2 or 4 h had no significant effect.

CONCLUSIONS

These results in healthy volunteers cannot be extrapolated directly to poisoned patients. However, they provide no evidence of efficacy for activated charcoal when administered after an interval of more than 2 h.

A prospective study of acute poisonings in Finnish hospital patients

1. We have carried out a prospective study of all adult patients presenting with acute poisoning during one month to the Helsinki University Central Hospital (Meilahti Hospital). 2. Two hundred and twenty-six cases of acute poisoning (113 males and 113 females) presented to the emergency department. Most cases in both men (66%) and women (67%) involved alcohol. As to drugs, psychotropic agents predominated in both men and women. The frequency of patient presentation peaked between 7 p.m. and 9 p.m. and was lowest between 8 a.m. and 10 a.m. In most cases, the delay from ingestion of the poison to presentation was longer than 4 h. 3. The clinical status of the patients on arrival was generally good; more than half (55%) of them were fully awake. Serious symptoms (e.g. unconsciousness, insufficient respiration necessitating intubation, aspiration, convulsions or hypotension) occurred in 15% of the presentations. There were no fatalities. 4. One hundred and thirty-five patients (60%) received at least one 50-g dose of activated charcoal. However, charcoal was given in 86% of the cases of drug poisoning. Gastric lavage was performed in 112 cases (50%), and 106 cases (47%) involved both gastric lavage and administration of charcoal. Twenty-one patients received antidotes (flumazenil, calcium gluconate or naloxone) and three patients were hemodialysed. 5. Of the 226 cases, 142 (63%) were managed solely in the emergency department. Of the 84 cases admitted to the hospital, eight had to be managed in the intensive care unit. Almost all patients (94%) were discharged within 24 h. 6. In this survey on 226 consecutive cases of acute poisoning, about two-thirds of the cases involved alcohol, while the most common drugs taken were psychotropic agents. The poisoning was mild in the great majority of the cases. Activated charcoal was generally administered in all but trivial cases of drug poisoning.