Abstract
Aims
Activated charcoal is now being recommended for patients who have ingested potentially toxic amounts of a poison, where the ingested substance adsorbs to charcoal. Combination therapy with gastric lavage and activated charcoal is widely used, although clinical studies to date have not provided evidence of additional efficacy compared with the use of activated charcoal alone. There are also doubts regarding the efficacy of activated charcoal, when administered more than 1 h after the overdose. The aim of this study was to examine if there was a difference in the effect of the two interventions 1 h post ingestion, and to determine if activated charcoal was effective in reducing the systemic absorption of a drug, when administered 2 h post ingestion.
Methods
We performed a four-limbed randomized cross-over study in 12 volunteers, who 1 h after a standard meal ingested paracetamol 50 mg kg−1 in 125 mg tablets to mimic real-life, where several factors, such as food, interfere with gastric emptying and thus treatment. The interventions were activated charcoal after 1 h, combination therapy of gastric lavage followed by activated charcoal after 1 h, or activated charcoal after 2 h. Serum paracetamol concentrations were determined by h.p.l.c. Percentage reductions in the area under the curve (AUC) were used to estimate the efficacy of each intervention (paired observations).
Results
There was a significant (P < 0.005) reduction in the paracetamol AUC with activated charcoal at 1 h (median reduction 66%, 95% confidence intervals 49, 76) compared with controls, and a significant (P < 0.01) reduction for gastric lavage followed by activated charcoal at 1 h (median reduction 48.2%, 95% confidence interval 32.4, 63.7) compared with controls. There was no significant difference between the two interventions (95% confidence interval for the difference −3.8, 34.0). Furthermore, we found a significant (P < 0.01) reduction in the paracetamol AUC when activated charcoal was administered 2 h after tablet ingestion when compared with controls (median 22.7%, 95% confidence intervals 13.6–34.4).
Conclusions
These results suggest that combination treatment may be no better than activated charcoal alone in patients presenting early after large overdoses. The effect of activated charcoal given 2 h post ingestion is substantially less than at 1 h, emphasizing the importance of early intervention.
Keywords: absorption reduction, activated charcoal, adsorption, gastric decontamination, gastric lavage, intoxication, paracetamol, poisoning
Introduction
Activated charcoal is a method of gastric decontamination that is now being recommended for patients who have ingested potentially toxic amounts of poison up to 1 h previously [1]. The effect of charcoal administered more than 1 h after overdose in a clinical setting appears to be uncertain [1, 2]. Clinical studies on poisoned patients have failed to show that outcome is improved in patients receiving a combination of gastric lavage followed by activated charcoal, when compared with patients treated with activated charcoal alone [3, 4]. Only one study has to date shown a slightly better clinical outcome for a small subset of patients who received the combination treatment, but small sample size and retrospective stratification limit the conclusions that can be drawn [5]. Based on these results, combined with a small number of experimental studies, gastric lavage is still recommended for patients with large potentially life-threatening overdoses, if they present within 1 h of ingestion [6]. Therefore, it is unclear if lavage should be followed by activated charcoal or charcoal should be used alone.
To our knowledge, only one study has determined the efficacy of lavage combined with charcoal in comparison with charcoal alone in preventing drug absorption in a controlled setting. Three different drugs in therapeutic doses were used [7]. No difference was found between combination treatment vs activated charcoal alone.
The purpose of our study was to evaluate whether there is a measurable difference in absorption between activated charcoal alone and a combination of lavage followed by activated charcoal, in patients presenting within 1 h of ingesting several grams of a drug. As the amount and type of drug ingested, and the time of ingestion are often very difficult to determine in a clinical setting, a study design using healthy subjects was chosen in order to provide a more controlled situation. We also wanted to investigate whether activated charcoal administered more than one hour after drug ingestion would affect systemic absorption. Since many factors influence the rate of gastric emptying and adsorption to activated charcoal in real life including alcohol and food [7–10]. our subjects were given a standardized semisolid breakfast meal 1 h before tablet ingestion.
Methods
The study protocol was approved by the local Ethics committee, The National Registry Board and the local hospital board. Approval from the Danish Medicines Agency was not necessary since activated charcoal is classified as being a medical utensil, while paracetamol was only being used as a marker. The subjects were under direct medical observation for the first 7 h after drug ingestion. The study was carried out at Bispebjerg University Hospital in Copenhagen. Twelve healthy adult volunteers participated in the study (Table 1), seven women and five men, mean age 28.6 years (range 22–39), and mean weight 71.8 kg (range 55–104). They had no history of hepatic, gastrointestinal or renal disease, no history of alcohol or drug abuse, and except for oral contraceptives in one female, no current use of medications. Written informed consent was obtained from each participant prior to enrolment in the study.
Table 1.
Individual characteristics of the subjects.
| Subject | Sex (M/F) | Age (years) | Weight (kg) |
|---|---|---|---|
| 1 | M | 39 | 78 |
| 2 | F | 22 | 65 |
| 3 | M | 28 | 75 |
| 4 | F | 34 | 60 |
| 5 | F | 23 | 63 |
| 6 | F | 26 | 65 |
| 7 | M | 33 | 81 |
| 8 | F | 30 | 55 |
| 9 | F | 22 | 60 |
| 10 | M | 26 | 104 |
| 11 | M | 29 | 86 |
| 12 | F | 31 | 70 |
Study design
A randomized crossover design was used, in latin square design, consisting of 4 study days separated by at least 1 week. Subjects were randomized at the time of inclusion. Definite dropouts were replaced by a stand-in, in which case the preceding sessions were rejected and subsequently repeated in the original sequence by the stand-in. There was only one dropout. On all study days, the subjects were given a standardized semisolid breakfast meal, and 1 h after completion of the meal, they received paracetamol. One of the study days served as the control arm, with no intervention being given (study day A). On the other study days, gastric decontamination was performed as either activated charcoal at 1 h after paracetamol ingestion (study day B), gastric lavage followed by activated charcoal at 1 h post ingestion (study day C) or activated charcoal at 2 h post ingestion (study day D). Paracetamol was chosen as the model-drug and given in nontoxic doses of 50 mg kg−1[11] in the form of standard paediatric tablets (8 mm in diameter), each consisting of 125 mg paracetamol (Pamol®, Nycomed, Denmark). The number of tablets given to each participant during each session ranged from 22 to 42.
Study day
All subjects arrived between 08.00 and 09.00 h following an overnight fast. A standardized semisolid breakfast meal weighing 325 g and containing 2265 kJ (540 kcal) made up of 15% protein, 30% fat, 55% carbohydrates was given, It did not contain any caffeine. One hour after the meal was finished, each subject was given paracetamol tablets with approximately 150 ml water. A light snack and water were served a minimum of 3 h after the intervention. Volunteers were ambulatory until the time of the intervention, after which they remained mostly supine.
Gastric decontamination
Activated charcoal consisted of Carbomix® (surface area 2.000 m2/g, Norit Cosmara, B.V., Amersfoort, the Netherlands) as a standard liquid preparation (50 g dose−1, 400 ml). The activated charcoal was a powdered aqueous preparation without sorbitol or other laxatives.
Gastric lavage consisted of a precautious aspiration, using only small amounts of tap water at ambient temperature, when the tube was suspected of being blocked [6]. An orogastric tube of 30 English gauge in circumference was placed, with two holes at the end, more than large enough to admit the undissolved tablets. Gastric lavage was performed by an anaesthetist and an intensive care nurse, both with experience in aspirating patients. The subjects were in a sitting position and gastric content was aspirated and saved for visual inspection. All subjects drank the activated charcoal solution immediately after the tube was removed.
Paracetamol assay
Blood samples were collected via an indwelling Teflon catheter inserted into a forearm vein. 5 ml blood samples were taken at 0, 15, 30, 45, 60, 90, 120, 180, 240, 300, 360 and 420 min approximately. Plain glass tubes were used, the samples were centrifuged and serum was frozen until analysis. Paracetamol concentrations were determined using high-performance liquid chromatography (h.p.l.c.). The quantification limit was 0.8 mg l−1. The coefficients of variation for repeated measurements were 2.9–7.5% [12].
Pharmacokinetics
The area under the serum drug concentration-time curve after the administration of paracetamol was calculated using the Winnonlin® software. A one-compartment model, first order kinetics with lag time, gave the optimal fit. The total area under the curve from 0 to ∞ (AUC(0,∞)) was calculated.
Statistical analysis
Results were expressed as median with ranges, and as the results were not normally distributed, nonparametric statistics were used for statistical analysis. A descriptive statistics program as part of the Winnonlin® software was used to calculate the nonparametric values. The Friedman test was employed, combined with the Wilcoxon test for post hoc comparisons. P values of <0.05 were considered to be statistically significant, and all results were adjusted by the Bonferroni method for multiple comparisons. 95% confidence intervals for major endpoints (e.g. absorption reductions, Cmax and C4 h concentrations) were calculated according to guidelines published by the British Medical Journal [13].
The number of subjects used was estimated on the basis of a desire to have a study with a power of 80% in order to detect a difference of at least 20% in the paracetamol AUC between all study days, at a significance level of 5%. Spearman's rank correlation method was used to estimate if any correlation existed between the absolute paracetamol dose and the reductions in paracetamol AUC after activated charcoal at 1 h.
Results
Basic pharmacokinetics for paracetamol were found to be in concordance with known values for the drug (Table 2). The t½ was unchanged for all interventions. No adverse reactions were noted.
Table 2.
Pharmacokinetic parameters for paracetamol.
| Control | Charcoal at 1 h | Lavage and charcoal at 1 h | Charcoal at 2 h | |
|---|---|---|---|---|
| tmax (h) | 1.7 (0.4–2.3) | 1.3 (0.7–3.1) | 0.9 (0.5–1.6) | 1.5 (0.7–2.3) |
| Cmax (mg l−1) | 41.8 (30.1–90.5) | 12.38 (7.2–58.7)* | 27.4 (4.1–62.2)* | 40.3 (11.8–56.1) |
| AUC(0,∞) (mg l−1 h) | 189.8 (119.1–235.4) | 52.9 (19.7–135.8)* | 88.1 (19.2–170.4)* | 151.7 (53.8–116.2)* |
| t½ (h) | 2.2 (1.1–3.3) | 1.7 (1.1–2.4) | 1.7 (1.3–2.0) | 1.8 (0.9–2.1) |
Data are given as median (range) for all 12 subjects.
Significantly different (minimum P < 0.05) from controls. ‘Control’ indicates day of ingestion of paracetamol without subsequent intervention.
Ingestion of activated charcoal 1 h after paracetamol ingestion
Activated charcoal administered 1 h after paracetamol intake significantly reduced the AUC(0,∞) of paracetamol compared with controls (P < 0.005), the median reduction being 66% (95% confidence intervals 49, 76.3). The Cmax was reduced by a median 61.8% (95% confidence intervals 29.8, 73.99; P < 0.01) (Figure 1).
Figure 1.
Median paracetamol concentrations (mg l−1) over time (min) for all subjects. Study day A (^) = control, e.g. paracetamol ingestion without intervention. Study day B (•) = activated charcoal administered 1 h after paracetamol ingestion. Study day C (▪) = gastric lavage followed by activated charcoal 1 h post ingestion. Study day D (□) = activated charcoal administered 2 h post ingestion.
The median concentration at 4 h was 23.2 mg l−1 (range 17.0–32.4) for the control arm without intervention and 6.3 mg l−1 (range 2.1–17.0) in the arm given activated charcoal 1 h after paracetamol ingestion. The median reduction in concentration at 4 h post ingestion was 67% (95% confidence intervals 54.0, 76.4) compared with the control arm.
Gastric lavage followed by activated charcoal 1 h after paracetamol ingestion
Combination therapy 1 h after tablet ingestion significantly reduced the AUC(0,∞) of paracetamol (P < 0.01) compared with the controls, the median reduction being 48.2% (confidence intervals 32.4, 63.7). The Cmax was reduced by a median of 32.9% (95% confidence intervals 10.8, 55.8; P < 0.02) (Figure 1). The median concentration at 4 h for this group was 9.5 mg l−1 (range 2.1–18.3), the median reduction in concentration compared with the control arm being 61.2% (95% confidence interval 41.2, 71.6).
Activated charcoal 2 h after paracetamol ingestion
Activated charcoal administered 2 h after paracetamol ingestion significantly (P < 0.01) reduced the AUC(0,∞) compared with controls, the median reduction being 22.7% (95% confidence intervals 13.6–34.4). The Cmax was reduced by a median of 9.7% (95% confidence interval −8.2, 31.8; NS) (Figure 1). The median concentrations at 4 h for this group was 16.7 mg l−1 (range 7.6–27), the median reduction in concentration compared with the control arm being 27.0% (95% confidence intervals 20.2, 38.3).
There was no statistically significant difference between the two interventions given 1 h post ingestion, although a trend was seen towards generally lower AUC values for the activated charcoal group only, with a median reduction in absorption of 14.8% in both arms compared with control values (95% confidence intervals −3.8, 34.0).
There was a statistically significant difference in the paracetamol AUC (P < 0.05) when activated charcoal was given after 1 h and 2 h, the effect of activated charcoal 2 h post ingestion being less than 40% (median 38.1% difference in absorption reduction) of that of activated charcoal after 1 h (95% confidence interval 16.0, 60.0) (Figure 2). At 4 h, the concentrations in the groups receiving charcoal at 1 h and 2 h showed the same pattern with a median reduction in absorption of 55.8% (95% confidence interval 32.4, 67.4) in favour of intervening 1 h post ingestion.
Figure 2.
Effect of activated charcoal administered 1 h after ingestion of paracetamol (study day B), of gastric lavage followed by activated charcoal 1 h post ingestion (study day C), and the effect of activated charcoal at 2 h post ingestion (study day D) vs control (study day A; paracetamol intake with no intervention), as measured by AUC (mg l−1 min) for paracetamol (median, 25% and 75% quartiles, and ranges). All interventions were significantly different from the control group (P < 0.05).
Discussion
The design of this study was intended to mimic real-life intoxications where patients have ingested a large number of tablets, the quantity of the drug reaching gram doses. A multiple cross-over latin square study design using healthy volunteers was chosen in order to control the amount and type of drug ingested and the time of ingestion. In real life, patients rarely present having ingested the drug or drugs on an empty stomach or after an overnight fast. We therefore included ingestion of a semisolid meal 1 h before the drug administration in our design. This design, where paracetamol is given in a supratherapeutic dose after a meal has been used once before, where the effect of activated charcoal at 1, 2 and 4 h, was studied [2]. The results of this study showed a significant reduction of 43% in the AUC(0,∞) when activated charcoal was given at 1 h, but no significant effect on AUC(0,∞) after that time. In contrast, there was a significant effect using the AUC between 4 and 9 h, when charcoal was administered at 1 and 2 h, showing a reduction in absorption of 56 and 22%, respectively. As the effect of a single dose of activated charcoal is mainly on the drug absorption, we felt that it would be more correct to use the AUC(0,∞). The fact that our study shows a better effect at 1 h, and a significant (although less of an) effect at 2 h post ingestion may be due to several factors. The caloric content of the standard meal used in our study might be higher than that used by Yeates & Thomas, which is not specified in their article [2]. It has previously been shown that a high caloric content slows the rate of gastric emptying [9], thus slowing drug absorption from the small intestine and increasing the exposure to activated charcoal. It has also been shown that delayed gastric emptying slows the absorption of paracetamol [14]. In our study, we used 125 mg paracetamol tablets in order to reach the number of tablets usually seen in overdose situations. It is unclear as to whether this contributed to the different results found in our study.
Paracetamol was chosen as a marker drug as it could be given in gram doses without reaching toxic levels. It has been shown to adsorb to charcoal, although charcoal has a higher adsorption capacity for most other drugs, at least in vitro [15]. In our study, the basic pharmacokinetics of paracetamol were in concordance with known values for the drug [16–18]. The gastric lavage was performed according to the position statement from the NAPCCT and EAPCCT [6], with only small amounts of water being used to dilute the stomach contents. As recently shown by Lapatto and coworkers [7], the combination of gastric lavage followed by charcoal was no more effective than charcoal alone, even though the volunteers were given the drugs in therapeutic doses and the intervention was 30 min after drug ingestion. Several clinical studies in overdose patients have reached a similar conclusion [3, 4] with the exception of one [5], where small samples sizes and retrospective stratification limit the conclusions that can be drawn. Gastric lavage on its own was not included in the study design, as the resulting reduction in the absorption of different drugs has been shown to be variable and less than when using activated charcoal [19–22]. Furthermore, its use as single agent for toxicologic gastrointestinal decontamination is no longer widely recommended [6].
We found that both types of interventions 1 h after tablet ingestion had a significant effect. There was no significant difference between the effect of activated charcoal alone or the combination of gastric lavage followed by activated charcoal, although a trend was found towards lower AUCs for activated charcoal alone. This may reflect the fact that the administration of activated charcoal after gastric lavage was delayed because of the time required for the lavage procedure. This procedure took approximately 10 min in all subjects, but most of the subjects also had their gag reflex activated, and the ensuing gastrointestinal movements may also have propelled their stomach contents into the small intestine.
The comparatively smaller reduction in absorption caused by activated charcoal administered 2 h after ingestion was expected, since even after a meal, paracetamol is fairly rapidly absorbed from the small intestine. It is not known whether the 20% reduction will be clinically significant, but several situations may slow gastric emptying, including coingestion of alcohol [11] and drugs that slow the rate of gastric emptying, thus increasing the effect of charcoal. The results from this experimental study suggest that the combination of activated charcoal and gastric lavage may be omitted from most cases of drug overdoses, as long as the drug ingested is adsorbed to activated charcoal.
Given that paracetamol is only moderately adsorbed to activated charcoal compared with other substances [15], the results from this study may be extrapolated to similar situations involving other drugs. It has to be remembered however, that we were using a simulated situation with volunteers, which will never completely resemble a clinical scenario where the patient has taken a large overdose.
A remaining issue is whether the dose of activated charcoal was large enough to adsorb the large gram doses of drugs ingested. The exact dose of activated charcoal needed has never been fully established, although a charcoal : drug ratio of 10 : 1 or a standard dose of 50 or 100 g to an adult is generally recommended. In this study, 50 g of charcoal and approximately 4 g of paracetamol were administered to our subjects in the presence of food in the stomach. The heavier subjects in our study who had larger absolute doses of paracetamol did not have a higher AUC, indicating that at least with paracetamol doses in the range of 2.75–5.2 g, a standard dose of 50 g of activated charcoal seems to be enough. Except for NSAIDs and antibiotics, few other drugs are taken in such high mass doses in overdose situations. In vitro studies in our laboratory simulating the gastric pH and contents have suggested an adsorptive capacity of charcoal for paracetamol at a much more favourable ratio than used clinically [12]. This may help in alleviating concern that the charcoal dose given will not be large enough to adsorb a substantial overdose.
In conclusion, the results of this experimental study suggest that combination treatment comprising gastric lavage followed by activated charcoal may be replaced by charcoal alone, even in patients presenting with larger overdoses who arrive within 1 h of drug ingestion. Even though there was an effect of activated charcoal more than 1 h post ingestion, the rapid decline in the reduction in absorption between the 1 h and 2 h interventions emphasizes the importance of fast decontamination procedures.
Acknowledgments
The study was performed with financial support from the Danish Research Councils. We want to thank our volunteers for their dedication to the project and their patience with the gastric tube. We thank Hanne R. Christensen for continued support and guidance.
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