Role of repeated oral doses of activated charcoal in clinical toxicology

The use of biochar in animal feeding

Biochar, that is, carbonized biomass similar to charcoal, has been used in acute medical treatment of animals for many centuries. Since 2010, livestock farmers increasingly use biochar as a regular feed supplement to improve animal health, increase nutrient intake efficiency and thus productivity. As biochar gets enriched with nitrogen-rich organic compounds during the digestion process, the excreted biochar-manure becomes a more valuable organic fertilizer causing lower nutrient losses and greenhouse gas emissions during storage and soil application. Scientists only recently started to investigate the mechanisms of biochar in the different stages of animal digestion and thus most published results on biochar feeding are based so far on empirical studies. This review summarizes the state of knowledge up to the year 2019 by evaluating 112 relevant scientific publications on the topic to derive initial insights, discuss potential mechanisms behind observations and identify important knowledge gaps and future research needs. The literature analysis shows that in most studies and for all investigated farm animal species, positive effects on different parameters such as toxin adsorption, digestion, blood values, feed efficiency, meat quality and/or greenhouse gas emissions could be found when biochar was added to feed. A considerable number of studies provided statistically non-significant results, though tendencies were mostly positive. Rare negative effects were identified in regard to the immobilization of liposoluble feed ingredients (e.g., vitamin E or Carotenoids) which may limit long-term biochar feeding. We found that most of the studies did not systematically investigate biochar properties (which may vastly differ) and dosage, which is a major drawback for generalizing results. Our review demonstrates that the use of biochar as a feed additive has the potential to improve animal health, feed efficiency and livestock housing climate, to reduce nutrient losses and greenhouse gas emissions, and to increase the soil organic matter content and thus soil fertility when eventually applied to soil. In combination with other good practices, co-feeding of biochar may thus have the potential to improve the sustainability of animal husbandry. However, more systematic multi-disciplinary research is definitely needed to arrive at generalizable recommendations.

Comparative study of the adsorption of acetaminophen on activated carbons in simulated gastric fluid

Samples of commercial activated carbons (AC) obtained from different sources: Norit E Supra USP, Norit B Test EUR, and ML (Baracoa, Cuba) were investigated. The adsorption of acetaminophen, Co = 2500 mg/L, occured in simulated gastric fluid (SGF) at pH 1.2 in contact with activated carbon for 4 h at 310 K in water bath with stirring. Residual acetaminophen was monitored by UV visible. The results were converted to scale adsorption isotherms using alternative models: Langmuir TI and TII, Freundlich, Dubinin-Radushkevich (DR) and Temkin. Linearized forms of the characteristic parameters were obtained in each case. The models that best fit the experimental data were Langmuir TI and Temkin with R(2) ≥0.98. The regression best fits followed the sequence: Langmuir TI = Temkin > DR > LangmuirTII > Freundlich. The microporosity determined by adsorption of CO2 at 273 K with a single term DR regression presented R(2) > 0.98. The adsorption of acetaminophen may occur in specific sites and also in the basal region. It was determined that the adsorption process of acetaminophen on AC in SGF is spontaneous (ΔG <0) and exothermic (-ΔHads.). Moreover, the area occupied by the acetaminophen molecule was calculated with a relative error from 7.8 to 50%.

The frequency of complications associated with the use of multiple-dose activated charcoal

STUDY OBJECTIVE

The objective of this study was to determine the frequency of complications associated with the use of multiple-dose activated charcoal.

METHODS

The study population was drawn from 8 tertiary care hospitals in 4 North American cities. Medical records of all inpatients between March 1993 and March 1998 with a discharge diagnosis of poisoning (International Classification of Diseases, 9th edition, Clinical Modification codes 960-989.9) were reviewed to select patients who had received multiple-dose activated charcoal (defined as > or =2 doses administered within 12 hours). Medical records of patients who received multiple-dose activated charcoal were reviewed for patient demographics and clinical information regarding the occurrence of pulmonary aspiration, gastrointestinal obstruction, hypernatremia, hypermagnesemia, corneal abrasion, and other complications associated with the use of multiple-dose activated charcoal.

RESULTS

We reviewed 6,258 medical records, identifying 878 patients who received multiple-dose activated charcoal. We judged 5 (0.6%; 95% confidence interval [CI] 0.1% to 1.1%) patients to have had clinically significant pulmonary aspiration and none (0%; upper 95% CI 0.3%) to have had gastrointestinal obstruction. None of the patients with pulmonary aspiration died or had residual sequelae recorded. Hypernatremia (peak serum sodium >145 mEq/L [145 mmol/L]) was documented in 53 (6.0%; 95% CI 4.4% to 7.6%) patients, of whom 5 (0.6%; 95% CI 0.1% to 1.1%) had a serum sodium concentration of greater than 155 mEq/L (155 mmol/L). Hypermagnesemia (peak serum magnesium >2.5 mg/dL [1.0 mmol/L]) was documented in 27 (3.1%; 95% CI 2.0% to 4.2%) patients, of whom 3 (0.3%; 95% CI 0.1% to 1.0%) had peak values that were greater than 3.75 mg/dL (1.5 mmol/L). One patient had a corneal abrasion (0.1%; 95% CI 0% to 0.6%). No other complications were identified.

CONCLUSION

Clinically significant complications associated with the use of multiple-dose activated charcoal occur infrequently.

Single-dose oral activated charcoal in the treatment of the self-poisoned patient: a prospective, randomized, controlled trial

Oral activated charcoal (OAC) is a universally accepted treatment of the overdose patient. Although the benefits of OAC have been suggested, there are no conclusive clinical data indicating that OAC affects outcome in overdose patients. This study was a prospective, randomized, controlled trial to determine the effects of OAC treatment in the self-poisoned adult patient. Adult patients presenting to the emergency department (ED) with a history of oral overdose were assigned to treatment with OAC (50 g) or supportive care only on an even-odd day protocol. Patients did not undergo gastric evacuation procedures in the ED. The outcome measures were clinical deterioration, length of stay in the ED or hospital, and complication rate. Over a 24-month period, 1479 patients were entered into the study. There were no significant differences in outcome parameters between the OAC treatment group and controls when comparing the length of intubation time, length of hospital stay, and the complication rates associated with the overdose. There was a higher incidence of vomiting and longer length of ED stay associated with OAC treatment. The results of this study indicated that oral drug overdose patients do not require gastric evacuation or charcoal administration. OAC provided no additional benefit to supportive care alone, was associated with a higher incidence of vomiting and a longer length of ED stay, and did not improve clinical outcome.

An in vitro evaluation of fluoxetine adsorption by activated charcoal and desorption upon addition of polyethylene glycol-electrolyte lavage solution

BACKGROUND

In drug overdoses, treatment with activated charcoal is frequently used because of its adsorptive properties. Recently, whole-bowel irrigation with polyethylene glycol-electrolyte lavage solution has been used as a gastrointestinal decontamination procedure for ingestions of toxins not well adsorbed to activated charcoal and for toxins with a delayed absorption phase, although well adsorbed to activated charcoal. While a combined approach using activated charcoal and whole-bowel irrigation could theoretically enhance the efficacy of both modalities, this improvement remains speculative, since data demonstrating its clinical advantage in overdose treatment are lacking. Fluoxetine, a selective serotonin uptake inhibitor, is one of the most frequently prescribed antidepressants. Fluoxetine is well adsorbed onto activated charcoal. This in vitro investigation was undertaken to study: a) the effect of polyethylene glycol, as well as polyethylene glycol-electrolyte lavage solution, on the adsorption of fluoxetine to laboratory grade-activated charcoal and a commercial activated charcoal formulation (Carbomix powder) in simulated gastric (pH= 1.2) and intestinal (pH=7.2) fluid environment; b) whether the order of polyethylene glycol-electrolyte lavage solution addition would have any effect on the adsorption of fluoxetine to activated charcoal.

METHODS

Adsorption of fluoxetine to charcoal in the presence of polyethylene glycol was examined: a) by the simultaneous addition of polyethylene glycol and charcoal to fluoxetine solution and b) by the addition of charcoal to fluoxetine solution and subsequent addition of polyethylene glycol. In both cases, the slurries were incubated at 37 degrees C for 1 hour and filtered. Free fluoxetine concentration was determined in the diluted filtrate by a reversed-phase high-performance liquid chromatography method.

RESULTS

The amount of fluoxetine adsorbed to activated charcoal (or Carbomix) was dramatically decreased at gastric and intestinal pH by the presence of polyethylene glycol or polyethylene glycol-electrolyte lavage solution added either concurrently or sequentially to activated charcoal.

CONCLUSIONS

In cases of fluoxetine overdose, administration of activated charcoal is recommended, while a combined approach using activated charcoal and whole-bowel irrigation with polyethylene glycol-electrolyte lavage solution is not recommended since it causes a significant desorption of the drug from activated charcoal.

Digoxin toxicity in chronic renal failure: treatment by multiple dose activated charcoal intestinal dialysis

1. Digoxin toxicity can result from overdose or iatrogenic causes, especially if renal function is impaired. 2. We present a case of digoxin toxicity presenting with severe bradycardia and hypotension in a 66 year old man with chronic renal failure. Regular haemodialysis had, as predicted, failed to reduce his plasma digoxin concentration. Digoxin specific antibody fragments (Fab) were not readily available and their use was probably inappropriate as they are normally renally eliminated. 3. The patient was successfully treated by two prolonged courses of intestinal dialysis with repeated doses of activated charcoal over 48 and 72 h and totaling 400 g and 600 g, respectively. However, the patient found the activated charcoal extremely unpalatable. 4. Multiple dose activated charcoal intestinal dialysis (MDACID) has been recently advocated for use in a wide range of poisonings. The technique takes advantage of the large surface area of the small intestine to eliminate drugs and metabolites, over several days if necessary. The pharmacokinetics of digoxin toxicity in chronic renal failure make intestinal dialysis an appropriate method of treatment but the realisation of the true potential of this technique awaits a more palatable absorbent or formulation.

Enhancement of lithium elimination by multiple-dose sodium polystyrene sulfonate

OBJECTIVE

To determine whether multiple doses of sodium polystyrene sulfonate (SPS) enhance the elimination of IV-administered lithium (Li).

METHODS

The study was a placebo-controlled, investigator-unblinded, murine trial of multiple doses of SPS on serum Li concentrations. Seventy-five male CD-1 mice were given IV pretreatment with LiCl (125 mg/ kg) followed by gavage treatments with SPS (5 g/kg/dose) 20, 40, 90, 150, and 210 minutes after LiCl (experimental group) or deionized water at equivalent times (control group). Subgroups of each treatment group were sacrificed at 1, 2, 4, and 6 hours after LiCl administration and blood was collected for Li analysis.

RESULTS

Statistical analyses indicated that the SPS group had lower serum Li concentrations overall than did the control animals. This difference was apparent at the 2-, 4-, and 6-hour time points.

CONCLUSION

In this murine model, repetitive doses of orogastric SPS enhanced the elimination of parenterally administered Li.

In vitro adsorption study of fluoxetine onto activated charcoal at gastric and intestinal pH using high performance liquid chromatography with fluorescence detector

BACKGROUND

This in vitro investigation was performed to study the adsorption characteristics of fluoxetine to activated charcoal and its commercial formulation Carbomix powder in simulated gastric (pH = 1.2) and intestinal (pH = 7.2) fluid environments.

METHODS

Solutions containing fluoxetine and charcoal were incubated at 37 degrees C for one hour. Reversed phase high performance liquid chromatography was used for the determination of free fluoxetine concentrations (range 0.2-8 micrograms/mL) in the diluted filtrate.

RESULTS

The maximum adsorption capacities at pH 1.2 for activated charcoal and Carbomix were 223 and 333 mg/g, respectively; at pH 7.2 they were 301 and 453 mg/g, respectively. The affinity constant values at pH 1.2 of activated charcoal and Carbomix were 441 and 122 L/g, respectively, while at pH 7.2 they were 482 and 589 L/g, respectively, indicating a strong binding of fluoxetine onto charcoals.

CONCLUSIONS

Relative to the toxic and lethal doses in cases of fluoxetine intoxications, both types of charcoals tested were found effective for adsorption at gastric and intestinal pH. Adsorbed fluoxetine was significantly increased at intestinal pH, consistent with predominant adsorption of the undissociated form of the drug. We conclude that activated charcoal and Carbomix have adsorptive properties appropriate to medical treatment in cases of fluoxetine overdose.

Multiple-dose activated charcoal in an accidental vancomycin overdose

BACKGROUND

Multiple-dose activated charcoal may enhance the enterocapillary clearance of vancomycin.

CASE REPORT

A 17-day-old female neonate born with congenital meningomyelocele and Arnold-Chiari malformation was iatrogenically overdosed with a 500 mg intravenous bolus of vancomycin during a shunt operation. The Red Man's Syndrome developed within minutes, characterized by sudden hypotension, skin rash and cyanosis. Serum vancomycin level at one hour after the injection was 165.7 micrograms/mL, as measured by an enzyme immunoassay method (EMIT). Multiple dose activated charcoal, 1 g/kg, was first given five hours after injection, and continued every four hours for 12 doses. The half-life of vancomycin during charcoal administration was calculated to be 9.4 h or less than the reported 13.4-33.7 h half-life in normal neonates. The neonate's renal function tests and brainstem auditory responses remained normal.

CONCLUSIONS

Gastrointestinal dialysis with multiple-dose activated charcoal without cathartics appeared to shorten the elimination half-life of vancomycin.

The effect of polyethylene glycol on the charcoal adsorption of chlorpromazine studied by ion selective electrode potentiometry

BACKGROUND

This investigation was undertaken to study: a) the adsorption characteristics of chlorpromazine to activated charcoal and its formulations Carbomix powder and Ultracarbon tablets at gastric pH; b) the effect on chlorpromazine adsorption of polyethylene glycol and its combination with electrolyte lavage solution; c) the effect of the order of addition of polyethylene glycol-electrolyte lavage solution.

METHOD

Ion selective electrode potentiometry, based on the selective, direct and continuous response of a chlorpromazine-ion selective electrode to the concentration of the free drug, was used. Successive additions of microvolumes of a chlorpromazine solution were made into a charcoal slurry in acidic medium of pH 1.2 with measurement of the chlorpromazine-ion selective electrode potential at equilibrium.

RESULTS

The maximum adsorption capacity values of activated charcoal, Carbomix and Ultracarbon, were 297, 563, and 382 mg/g respectively, while the affinity constant values were 40.2, 70.4, and 40.5 L/g, respectively. The adsorption of chlorpromazine to each of the Ultracarbon and Carbomix components was compared to the total adsorption of the formulations. The addition of polyethylene glycol-electrolyte lavage solution causes a slight desorption of chlorpromazine from activated charcoal at gastric pH, more pronounced when polyethylene glycol-electrolyte lavage solution follows the addition of activated charcoal, suggesting the possibility of a nonspecific binding of chlorpromazine to polyethylene glycol. The amount of chlorpromazine absorbed to Carbomix and Ultracarbon was not significantly affected at gastric pH by the presence of polyethylene glycol or polyethylene glycol-electrolyte lavage solution added either concurrently or sequentially to these formulations.

Effect of multiple-dose activated charcoal on the clearance of high-dose intravenous aspirin in a porcine model

STUDY OBJECTIVE

To study the effect of multiple-dose activated charcoal (MDAC) on salicylate clearance in pigs given high-dose i.v. aspirin.

DESIGN

In a crossover design, six fasted pigs received 300 mg/kg i.v. aspirin followed by no treatment or MDAC (1 g/kg hourly for 6 doses by gastrostomy). Serum salicylate samples were obtained every 30 minutes for 6 hours.

RESULTS

The mean peak salicylate concentrations were 47.4 +/- 6.2 mg/dL and 48.4 +/- 3.9 mg/dL (P = .74), and the areas under the time-serum salicylate concentration curve over 6 hours were 171,000 +/- 24,000 mg.minute/L and 188,000 +/- 18,000 mg.minute/L for the control and treatment arms, respectively (P = .22). This study had a 90% power to detect a 30% difference between arms.

CONCLUSION

MDAC does not enhance the clearance of salicylate after administration of high-dose i.v. aspirin.

Prevention of drug absorption in simulated theophylline overdose

1. The effects of emesis, gastric lavage and oral activated charcoal on theophylline absorption were compared in healthy volunteers. 2. One of four regimes (ipecacuanha-induced emesis, gastric lavage, oral activated charcoal and no treatment) was randomly chosen one hour after a simulated overdose with sustained-release theophylline on four separate occasions in twelve healthy volunteers. 3. Syrup of ipecacuanha produced emesis in all twelve volunteers but only seven vomited any tablets. Gastric lavage yielded tablets in only one volunteer. 4. The mean systemic availabilities (areas under the concentration-time curves relative to control) of theophylline for ipecacuanha-induced emesis, gastric lavage and charcoal, were 107.1%, 101.1% and 16.9%, respectively. 5. Oral activated charcoal was thus highly effective, while gastric lavage and emesis were ineffective in preventing theophylline absorption. Activated charcoal is potentially the most effective first-line treatment for acute overdosage with sustained-release theophylline tablets.

Prevention of drug absorption in simulated theophylline overdose

To assess the effectiveness of oral activated charcoal and catharsis in preventing theophylline absorption, 12 healthy subjects, aged 20-35 years, received 3 x 200 mg sustained-release theophylline tablets and 16 radio-opaque placebo tablets on six occasions. On each occasion, they received either no treatment (control) or one of five treatments. Treatments were a) oral activated charcoal (Carbomix): 50 g at 1 h, 25 g at 5 h and 9 h; b) sorbitol 70%: 150 mL at 1 h; c) activated charcoal: 50 g at 6 h, 25 g at 10 h and 14 h; d) sorbitol 70%: 150 mL at 6 h; e) charcoal commencing at 6 h plus sorbitol at 6 h (i.e. a combination of treatments c and d). Plasma theophylline concentrations were measured and all stools collected over 36 h to assess placebo tablet recovery by radiography. Charcoal administration at 1 h was 91.2% effective in preventing theophylline absorption and at 6 h was 57.3% effective, while combined charcoal and catharsis at 6 h was 63.3% effective. Sorbitol-induced catharsis at 1 h and 6 h did not reduce theophylline absorption despite greater tablet recovery. Oral activated charcoal may be the most effective treatment for sustained-release theophylline overdose, with maximum benefit when administered soon after an overdose, though later administration might still be of value. Sorbitol catharsis is of no benefit either alone or in combination with charcoal.

Clinical approach to toxicities

Toxicities are a common presenting complaint in the emergency department. This article discusses the clinical approach to the poisoned patient from the initial telephone call by the owner to presentation, management, and monitoring of the patient in the emergency department. Topics discussed include telephone triage, diagnosis, management, and monitoring of the poisoned patient.

Paracetamol (acetaminophen) poisoning

Paracetamol poisoning caused by intentional overdose remains a common cause of morbidity. In this article the mechanism of toxicity and the clinical effects and treatment of poisoning, including specific antidotal therapy, are reviewed. Areas for further research directed at reducing morbidity and mortality from paracetamol poisoning are considered.

Effect of saline cathartics on gastrointestinal transit time of activated charcoal

The effects of saline cathartics on the gastrointestinal transit time of activated charcoal were investigated in six healthy volunteers. The study shows that the mean gastrointestinal transit times of charcoal alone were 29.3 h and 24.4, 15.4, 17.3 and 17.5 h with sodium chloride, sodium sulphate, magnesium sulphate alone and Andrew's Liver Salt respectively. Some volunteers complained of slight abdominal discomfort in all the phases except the Andrew's Liver Salt phase.

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.

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.

Management of theophylline overdose patients in the intensive care unit

In a retrospective survey of all adults admitted to the Intensive Care Unit with acute theophylline poisoning over the last five years, we identified 38 patients (6.8% of all admissions for poisoning), two of whom died. Thirty-five (92%) had taken a sustained-release preparation. Eight patients had grand mal seizures and six developed arrhythmias (ventricular fibrillation, 3; atrial fibrillation, 2; supraventricular tachycardia, 1). Severe vomiting was present in 34 (89%) and proved to be a serious obstacle to the administration of enteral charcoal. The vomiting was controlled by intravenous metoclopramide in seventeen patients (50%), but the remaining seventeen required mechanical ventilation with sedation and muscle relaxation for the effective delivery of nasogastric charcoal. Importantly, in nine (24%), the serum theophylline concentration continued to rise despite enteral charcoal. Charcoal haemoperfusion was used in seven (18%). We present an algorithm for the management of severe, acute theophylline poisoning.

Multiple-dose sodium polystyrene sulfonate in lithium intoxication: an animal model

Previous work in our laboratory has demonstrated that sodium polystyrene sulfonate (SPS) significantly lowered serum lithium (Li) concentrations when administered in a single oral dose after an oral dose of lithium in a mouse model. The present study was designed to determine whether: 1) repetitive doses of SPS are effective in lowering serum lithium concentrations, 2) the effect of SPS on lithium concentration is dose related and 3) SPS enhances the elimination of lithium. Mice (N = 144) were given orogastric LiCl (250 mg/kg) and then divided into 4 groups: Controls received water 0, 30, 90, 180, and 360 min. after LiCl; the Full-Dose SPS Group received SPS (5 g/kg/dose) at equivalent times; the Half-Dose SPS Group received SPS (2.5 g/kg/dose) at the same times; and the Elimination Group received water at 0 and 30 min. after LiCl and SPS at 90, 180 and 360 min. after LiCl. Subgroups of each group were sacrificed at 1, 2, 4 and 8 hr post-treatment and serum analyzed for lithium concentrations. Statistical analyses revealed that, when compared to Controls: 1) SPS significantly lowered serum lithium concentrations; 2) this effect was dose-related; 3) repetitive dosing of SPS appears to enhance the elimination of lithium.

[Oral administration of activated charcoal-sorbitol suspension as first aid in prevention of poison resorption?]

Due to its paramount adsorption capacity, activated charcoal is supposed to be the remedy of choice for binding a variety of drugs in the gastrointestinal tract. Hence it is surprising--at least according to the advice of German textbooks--that activated charcoal is only recommended for administration after time-consuming treatments like induced emesis and gastric lavage. Particularly with infants at home, a ready-for-use suspension of activated charcoal would allow the early management of acute poisoning. In such cases, inactivation of the poison by adsorption could be particularly helpful, since the period after ingestion is usually short. The charcoal-sorbitol-suspension (30 g activated charcoal in 150 ml of 70% sorbitol) is a creamy preparation which is easy to drink, because density and viscosity prevent sedimentation. The prescription-free drugs can be dispensed by each pharmacist. The present study was undertaken to investigate the influence of sorbitol on the adsorption capacity of activated charcoal. To this end, adsorption isotherms were established in vitro and compared with results in volunteers to whom NAPAP, diphenhydramine or codeine was administered separately. These drugs are gaining increasing importance in medicinal toxicology since they are constituents of various analgesics and cold remedies. To determine absorption, the cumulative urinary excretion was estimated of the parent drugs and their main metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple doses of activated charcoal: time for reappraisal?

Multiple-dose charcoal therapy has become a popular treatment for many overdoses. It is generally perceived as a simple, inexpensive, effective, and safe procedure that decreases morbidity and mortality by enhancing drug excretion. However, increased drug clearance has been shown definitively for only a few drugs, and improved outcome has not been demonstrated conclusively for any overdose. Recently, there have been several reports of complications due to this intervention. The role of this pharmacologic curiosity in the management of the acutely poisoned patient requires reassessment.

Dealing with plant poisoning of livestock: the challenge in Queensland

The current and possible future situation of diagnosis, prevention and treatment of plant poisoning of livestock in Queensland is reviewed. Topics discussed are livestock producers' perceptions, field investigation, plant identification, veterinary laboratory techniques and prevention through knowledge of poisonous species and the circumstances of poisoning. Also considered are management strategies for prevention including the manipulation of rumen flora and epidemiological approaches, therapies including immunisation, plant control and sources of information on poisonous plants and poisoning.

Interaction between whole-bowel irrigation solution and activated charcoal: implications for the treatment of toxic ingestions

STUDY OBJECTIVES

The purpose of this study was to address the issues of safety and efficacy of combining whole-bowel irrigation and activated charcoal administration for the treatment of toxic ingestions.

STUDY DESIGN

Two in-vitro studies were performed. In the first, serial ratios of polyethylene glycol (PEG) and activated charcoal (AC) powders were added to water and the solutions were analyzed for PEG concentration and osmolality. In the second, serial ratios of a pharmaceutical bowel irrigation solution and an AC preparation were combined with a constant amount of salicylic acid. Solution osmolalities, PEG, and salicylic acid concentrations were then quantified.

RESULTS

Adsorption of PEG powder by AC was demonstrated; however, changes in solution osmolality were negligible. Thus, concurrent administration of these therapies appears safe. However, combining bowel irrigation solution with AC resulted in decreased salicylic acid adsorption. This was especially so with smaller amounts of AC that would pertain more to the smaller doses of AC used for multiple-dose charcoal therapy.

CONCLUSION

If these in-vitro data are applicable to overdose patients, the administration of a routine initial charcoal dose to those who will be treated with whole-bowel irrigation would be appropriate. However, it is unlikely that the addition of multiple-dose charcoal therapy to whole-bowel irrigation would provide additional benefit for the patient.

Role of repeated doses of oral activated charcoal in the treatment of acute intoxications

While single dose activated charcoal is effective in preventing drug absorption, repeated doses not only prevent absorption but also can increase systemic drug clearance. The mechanism for the latter effect may involve interruption of enterohepatic recycling and/or promotion of drug exsorption from the systemic circulation into the gut lumen. A comprehensive review of reported studies in volunteer subjects and overdose patients showed that repeated dose activated charcoal markedly decreased the half-life and/or increased the clearance of a wide range of drugs. Side-effects of the treatment were infrequent, but included aspiration pneumonia, diarrhoea and constipation. The addition of laxatives to repeated dose charcoal treatment did not offer any significant increase in drug clearance and is not recommended. It is suggested that the optimal regimen for the use of repeat dose activated charcoal in acute drug intoxications is an initial dose of 75-100 g, followed by 50 g every 4 hours until the risks of systemic drug toxicity are reduced to an acceptable level.

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.

Serum magnesium concentrations after repetitive magnesium cathartic administration

Severe hypermagnesemia has been reported by several authors after multiple doses of magnesium-containing cathartic are administered during management of a toxic ingestion. To evaluate the frequency and magnitude of serum magnesium elevations after the use of repetitive magnesium catharsis, we prospectively evaluated 102 patients who received multiple doses of magnesium citrate as a part of treatment of an overdose. Commonly ingested substances for which repetitive cathartic was administered were tricyclic antidepressants in 47%, aspirin in 17%, and phenytoin in 10%. For each case, serial electrolytes, blood urea nitrogen, creatinine, calcium and magnesium were obtained. Mean initial serum magnesium concentration was 1.8 +/- .03 mEq/L. After a mean 960 mL of magnesium citrate (9.22 g magnesium), final mean serum magnesium concentration was 2.5 +/- .05 mEq/L. Forty-seven patients (47%) developed an elevated (greater than 2.4 mEq/L) serum magnesium concentration, with 12 greater than 3.0 mEq/L. No correlation was found between total quantity of magnesium citrate administered and the increment in serum magnesium concentration. Our data indicate that serum magnesium concentrations consistently rise after repetitive magnesium citrate use. However, the magnitude of this rise appears modest. The elevation in serum magnesium concentration does not correlate with the quantity of magnesium administered. We conclude that with close monitoring, repetitive magnesium citrate can be administered without inducing severe hypermagnesemia (serum magnesium concentration greater than 5.0 mEq/L).

Management of toxicoses

This article provides information on the detoxification of and supportive care for poisoned animals. Involved are measures to control life-threatening manifestations of toxicoses, to remove agents from the digestive tract, skin, or eyes, and to promote removal of systemically absorbed toxicants. The use of these methods is often of paramount importance in an effort to limit organ damage and to enable a poisoned animal to survive.

Administration of activated charcoal or sodium polystyrene sulfonate (Kayexalate) as gastric decontamination for lithium intoxication: an animal model

To determine whether sodium polystyrene sulfonate (SPS; Kayexalate) is effective in decreasing the absorption of lithium (Li) and to test the assumption that Li is poorly adsorbed by activated charcoal, 130 mice were administered an orogastric dose of LiCl (250 mg/kg) followed immediately by orogastric SPS (10 g/kg, SPS Group), activated charcoal (6.7 g/kg, AC Group), or water in an equivalent volume (Control Group). Subgroups of each of the 3 groups were sacrificed at 1, 2, 4 and 8 hr after treatment and serum analyzed for Li concentration. Statistical analyses revealed no overall difference between the AC Group and the Control Group. However, the SPS Group differed from both the Control and the AC Group at each time interval, with Li concentrations significantly lower in the SPS Group. These results demonstrate that: 1) SPS, in this study, effectively reduced serum Li concentrations in an in vivo model, and 2) activated charcoal did not.

Central nervous system manifestations of a valproic acid overdose responsive to naloxone

We report the case of a 22-year-old man who presented with a depressed level of consciousness after ingesting valproic acid. He responded to IV naloxone; over a nine-hour period, his serum valproic acid level decreased from 180.4 to 59.2 micrograms/ml with multiple-dose charcoal therapy. We recommend the use of both agents in the treatment of valproic acid overdose.

Pharmacokinetic modelling of the effect of activated charcoal on the intestinal secretion of theophylline, using the isolated vascularly perfused rat small intestine

The effect of activated charcoal administration on the secretion of theophylline from the blood into the intestinal lumen has been examined by use of the rat isolated vascularly perfused small intestine. A closed two compartment model was used to analyse the vascular and luminal concentration-time curves obtained. An equation was derived to calculate the time-dependent intestinal clearance. From control experiments it was concluded that theophylline is secreted by a diffusional transport system through the intestinal wall. The intestinal clearance declined rapidly with time as a result of the concomitant increase in luminal theophylline concentration. After 120 min a steady state between the vascular and luminal perfusate was established. Administration of activated charcoal in the lumen had a profound effect on the kinetics of the drug. The vascular steady state concentration was depressed dramatically. The theophylline clearance remained nearly constant with time, because the blood to lumen concentration gradient was maximized. The maximal value for the intestinal theophylline clearance was estimated to be 0.88 mL min-1 and it equalled the value for the intestinal blood flow at the absorptive site. By use of the concept of absorptive site blood flow, the maximal effect of charcoal on systemic theophylline clearance could be adequately predicted for rats, dogs and man. Activated charcoal administration is only useful to enhance the systemic clearance of drugs or toxicants if that clearance is of the same order of magnitude as the absorptive site blood flow or lower.

A ready-to-use activated charcoal mixture. Adsorption studies in vitro and in dogs: its influence on the intestinal secretion of theophylline in a rat model

A practical, ready-to-use preparation of activated charcoal (AZU mixture) for application in toxicology has been formulated. To establish its efficacy, the formulation was tested in vitro and in dogs. The in vitro adsorption capacity was compared to that of freshly prepared charcoal suspension in water (CW) and to Carbomix. Langmuir adsorption coefficients demonstrated small but clinically insignificant differences in adsorption capacity between the preparations. The laxative sodium sulfate did not reduce the adsorption capacity of charcoal in vitro. Dogs were given 60 mg of paracetamol per kg as an oral solution followed by 5 g of activated charcoal preparation. The area under the plasma concentration versus time curve (control 2955 +/- 353 mg.min-1.l-1) was significantly reduced following CW (921 +/- 453) and AZU (786 +/- 270). The premixed AZU charcoal formulation is efficacious, inexpensive and overcomes the problems of bed-side preparation. An isolated vascularly perfused rat small intestine can be used to describe the effect of activated charcoal on the intestinal secretion of theophylline.

An evaluation of the effect of repeated doses of oral activated charcoal on salicylate elimination

The authors investigated the effect of repeated doses of oral activated charcoal on salicylate elimination in six healthy volunteers. On two occasions (phase I and phase II; separated by one week) each subject received 1300 mg of aspirin as an aqueous solution. On the second occasion (phase II) each subject also received a total dose of 55 g of aqueous activated charcoal initiated 4 hours after salicylate administration (25 g initial dose, followed by three 10 g doses at two hour intervals). Serum salicylate levels were measured from one to twelve hours post aspirin ingestion. The pharmacokinetic analysis showed no significant change between phase I and phase II for either the salicylate elimination half-life or the area under the concentration versus time curve from 4-12 hours post aspirin ingestion. Reasons for the lack of effect of repeated doses of charcoal on salicylate elimination are discussed and, these results cannot necessarily be extrapolated to the overdose situation. Further investigation is warranted to assess the effect of repeated doses of activated charcoal in the salicylate-overdosed patient.

Hypermagnesemia associated with catharsis in a salicylate-intoxicated patient with anorexia nervosa

While clinicians have raised concerns about giving multiple doses of a cathartic as a part of therapy for acute poisoning, fears of excessive magnesium absorption or fluid or electrolyte imbalances have been largely unrealized. We present the case of a 19-year-old woman with anorexia nervosa and long-term laxative abuse who, despite a normal baseline serum magnesium concentration, developed hypermagnesemia during treatment with multiple doses of activated charcoal-magnesium citrate for acute salicylate intoxication. The peak serum magnesium concentration, after two doses of magnesium citrate, reached 9.8 mg/dL (4.0 mmol/L). It fell to normal levels when sorbitol was substituted as a cathartic and after the patient had been hemodialyzed for symptoms of salicylate toxicity that continued despite conventional therapy. While disordered magnesium metabolism in one patient with a severe underlying medical condition should not interdict the use of repetitive doses of magnesium citrate as a cathartic, patients requiring such therapy should have serum magnesium concentrations measured serially to monitor for signs of magnesium loading.

Gastrointestinal transit times of a charcoal/sorbitol slurry in overdose patients

Gut decontamination with a slurry of activated charcoal and sorbitol is one of the methods presently available to decrease total body burden of ingested drug. This one year retrospective audit of patients presenting with a history of recent toxic ingestion was designed to determine the time to stool of a charcoal/sorbitol slurry (CSS) when used for differing ingestants. A total of 69 patients received a CSS. 50.7% took less than 6 hours for their first charcoal stool, while 26.1% had emesis of the CSS within 30 minutes of administration. Ingestion of drugs which may increase gastrointestinal transit time (i.e. opioids, cyclic antidepressants) correlated with prolonged time to stool despite treatment with the CSS. Though a prospective, controlled study needs to be performed, variation in dosage of the CSS may be appropriate in select patient groups to offset the effects of the ingestant on bowel motility.

The management of acute poisoning due to beta-adrenoceptor antagonists

Although many cases of beta-adrenoceptor antagonist (beta-blocker) poisoning are uneventful, a proportion develop serious and sometimes fatal cardiovascular system depression with severe hypotension. As beta-adrenergic tone is not essential for cardiovascular function in health, there is no physiological reason why total beta-adrenoceptor blockade should have serious consequences in the resting individual. The toxic actions of beta-blockers appear to be related to properties such as membrane depressant activity and possibly due to actions on beta-adrenoceptors distinct from those in the cardiovascular system. Most reports of serious adverse effects following overdosage concern beta-blockers with significant membrane depressant activity, and in particular propranolol and oxprenolol, with which progressive heart block and bradycardia are features. Sotalol toxicity, with its unique electrophysiological action, is a special case. Animal experiments confirm that beta-blockers with membrane depressant activity are more toxic than the newer more selective ones, such as atenolol and nadolol. However, experimental models also reveal that artificial ventilation markedly reduces the toxicity of all beta-blockers tested, suggesting a respiratory depressant action with very high doses. Treatment of serious overdosage in man should include maintenance of adequate ventilation. High dose intravenous glucagon is recommended, because its inotropic action depends on direct stimulation of adenylate cyclase. beta-Agonists such as isoprenaline (isoproterenol) or prenalterol may be effective, but the nature of agonist-competitive antagonist interactions may necessitate the use of unrealistically large doses to overcome very high tissue beta-blocker concentrations.

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)

Evaluation of the effects of multiple-dose activated charcoal on the absorption of orally administered salicylate in a simulated toxic ingestion model

The effects of multiple-dose activated charcoal administration on the absorption of orally administered salicylate were evaluated in a simulated overdose model. Thirteen adult volunteers were each given 24 81-mg aspirin tablets during a control phase, and during three randomized treatment periods the volunteers received 50 g activated charcoal for one, two, or three doses (separated by four hours). The control phase and treatment periods were separated by a one-week interval. Urine was collected for 48 hours to determine percent total salicylate excretion. Ten subjects completed all four phases of the study. Mean +/- SD percent recovery of salicylate from urine was: control, 91.0 +/- 6.12; one-dose charcoal, 68.3 +/- 12.46; two-dose charcoal, 65.9 +/- 13.48; and three-dose charcoal, 49.2 +/- 12.48. Each charcoal treatment significantly lowered the absorption of aspirin as compared with the control (P less than .01). There was no significant difference between one-dose and two-dose charcoal regimens. There was a statistically significant decrease in salicylate absorption with the three-dose charcoal regimen as compared to one-dose and two-dose regimens (P less than .01). We conclude that activated charcoal is effective in inhibiting absorption of orally administered salicylate, in a small-dose aspirin ingestion model, with a three-dose multiple charcoal regimen being superior to either single-dose or two-dose regimens.

Curing experimental Bryophyllum tubiflorum poisoning of cattle with activated carbon, electrolyte replacement solution and antiarrhythmic drugs

A slurry of activated carbon (activated charcoal) in electrolyte replacement solution given by stomach tube and antiarrhythmic drugs given parenterally cured 9 of 11 calves dosed 7 to 24 h previously with a lethal amount (20g/kg) of Bryophyllum tubiflorum flower heads. Two of another 4 calves treated 26 to 36 h after dosing with flowers survived. B. tubiflorum toxins are bufadienolides (cardiac glycosides). Activated carbon was effective at a single dose of 5 g/kg. Calves were rehydrated with oral electrolyte replacement solution at 150 ml/kg in divided doses over 24 h. Tachycardia was treated with intravenous lignocaine (200 mg doses) or propranolol (5 mg doses) and atrioventricular block with atropine (0.5 mg/kg).

Role of extracorporeal drug removal in acute theophylline poisoning. A review

Theophylline, with its narrow therapeutic margin, is a common cause of iatrogenic and deliberate overdose. Most cases of self-poisoning are with sustained release preparations, with peak concentrations occurring up to 12 or more hours after overdose. Toxic symptoms are often seen at concentrations above 15 mg/L. Theophylline is metabolised within the cytochrome P-450 system, with an average total body clearance of 50 to 60 ml/min. Clearance is, however, affected by many factors such as other drugs or disease, and in overdose zero order kinetics may result in prolonged half-lives. Toxicity is characterised by agitation, tremor, nausea, vomiting, abdominal pains, seizures, and tachyarrhythmias. Hypokalaemia and metabolic acidosis are more profound in acute toxicity, and hypercalcaemia is usually present. Seizures occur at lower concentrations after chronic over-medication than after acute overdose. Gastric lavage should be performed in all patients presenting early, and an oral multiple dose charcoal regimen started with 50 to 100g charcoal, repeating with 50g doses and checking theophylline concentrations at 2- to 4-hour intervals. Multiple dose charcoal can be expected to double the clearance of theophylline, being as effective as a haemodialysis. Of the invasive techniques available, charcoal haemoperfusion is the most effective, increasing clearance 4- to 6-fold. Supportive care is particularly important. The aggressive supplementation of potassium, treatment of emesis with droperidol and ranitidine, and treatment of tachyarrhythmias and hypotension (possibly with propranolol), together with oral multiple dose charcoal may obviate the need for haemoperfusion. Seizures suggest increased morbidity and mortality. Charcoal haemoperfusion should be considered if plasma concentrations are greater than 100 mg/L in an acute intoxication or greater than 60 mg/L in a chronic intoxication. The decision to haemoperfuse should not be based on plasma concentrations alone, but an overall evaluation of the patient's laboratory and clinical status.