Acetaminophen toxicity in children: diagnostic confirmation using a specific antigenic biomarker

Chronic acetaminophen (APAP) toxicity poses a difficult diagnostic challenge to the clinician. Signs and symptoms are nonspecific and no currently available laboratory study can confirm APAP as the causative agent of hepatic injury. In this study an antigenic biomarker for APAP toxicity was used to confirm the diagnosis of APAP-induced hepatic failure in two children with chronic APAP toxicity. APAP that has been metabolized to N-acetyl-benzoquinone imine (NAPQI) reacts with cellular proteins to form 3-(cystein-S-yl)-APAP protein adducts (3-Cys-A). Serum from both patients was submitted for quantitation of 3-Cys-A by a competitive inhibition enzyme-linked immunosorbent assay (ELISA). Concentrations of 3-Cys-A in the two patients were 1.97 and 2.77 nmol/mg protein, which are similar to concentrations found in adults with hepatic injury secondary to an overdose of APAP. Individuals with no exposure to APAP have no detectable 3-Cys-A in serum. It was concluded that 3-Cys-A is a useful marker of APAP intoxication after long-term ingestion of APAP when total dose and time course of ingestion are uncertain, and may prove to be a useful clinical and investigative tool in the study of APAP intoxication.

Treating paracetamol overdose by charcoal haemoperfusion and long-hours high-flux dialysis

After serious paracetamol overdose, charcoal haemoperfusion was used to remove paracetamol from the circulation, aiming to reduce the severity of subsequent hepatic damage. Daily long-hours high-flux dialysis was given to patients with grade III-IV hepatic encephalopathy, and also to those at risk of developing encephalopathy. We reviewed patients treated in this manner who had not received N-acetylcysteine within the first 15 h after overdose. From January 1983 to January 1993, 73 patients with serious paracetamol overdose were seen, of whom 51 received charcoal haemoperfusion and/or high-flux dialysis. Patients who were admitted within the first 42 h after overdose and who received haemoperfusion and/or dialysis had significantly lower peak levels of prothrombin time, bilirubin and creatinine than those who were admitted after 42 h. Mortality was also lower amongst patients admitted before 42 h, at 2/18 (11%) vs. 15/33 (45%), p < 0.05.

Measurement of aspirin and paracetamol metabolites

Clinical laboratories are frequently asked to measure the concentration of drugs in blood and urine. Of the many thousands of drugs prescribed, however, the measurement of only a relatively small number provides useful clinical information. There are three main reasons for measuring drugs: to test patient compliance, to ensure that dosage is high enough to have therapeutic effect but sufficiently low to avoid toxicity and, finally, to identify drugs taken during deliberate or accidental overdose. This article is concerned with the last of these.

Paracetamol overdose: pathophysiology and nursing management

Paracetamol overdose now represents one third of all self-poisoning cases. In contrast to other drugs, the use of paracetamol as a self-poisoning agent is increasing. As very large doses of the drug cause severe liver injury, which can result in fulminant hepatic failure when left untreated, it is essential that nurses have a complete understanding of the mechanisms of normal paracetamol metabolism, effects of overdosage and treatment strategies to guide the nursing management of clients. This review therefore critically examines the pathophysiology and nursing management of clients with acute paracetamol overdosage.

The use of ondansetron in the treatment of nausea and vomiting associated with acetaminophen poisoning

BACKGROUND

Nausea and vomiting associated with poisoning can complicate treatment and in some cases delay potential antidote administration. Side effect such as lowering the seizure threshold may at times discourage the use of traditional phenothiazine and butyrophenone antiemetics.

METHODS

We performed a prospective, single arm, observational study examining the effectiveness of the 5HT3 receptor antagonist ondansetron in the management if nausea and vomiting associated with acetaminophen poisoning. Patients with a history or laboratory evidence of acetaminophen poisoning were eligible for inclusion in the study. Exclusion criteria included age less than 18 or greater than 65, use of other antiemetic therapy within the previous 12 hours, history of preexisting hepatic or hematologic disease, pregnancy, or significant ingestion of other substances. Upon meeting entry criteria, patients were administered 8 mg of intravenous ondansetron. Nausea was graded on a 100 mm scale with number of emetic episodes recorded before and after treatment.

RESULTS

Six patients were entered in the study. All patients had nausea and at least one emetic episode prior to ondansetron and prior to administration of N-acetylcysteine. All patients reported relief of nausea after ondansetron. The degree of nausea decreased by an average of 52% at 30 min and 88% at 60 min following ondansetron administration. No significant vital sign changes were recorded in any patient, and there were no complications related to therapy. Three patients were administered N-acetylcysteine, and all tolerated this therapy without vomiting after ondansetron.

CONCLUSIONS

Ondansetron appears to be a potentially useful adjunct in the management of nausea and vomiting associated with acetaminophen poisoning.

Hemolysis after acetaminophen overdose in a patient with glucose-6-phosphate dehydrogenase deficiency

CASE REPORT

A sixteen year-old-male with a history of glucose-6-phosphate dehydrogenase deficiency ingested an unknown amount of acetaminophen and presented to an emergency department 7.5 h later. He was afebrile. His serum acetaminophen level was 184 micrograms/mL, and his urine toxicologic screen was otherwise negative. Vomiting led to enrollment in a experimental protocol of intravenous N-acetylcysteine. He developed no evidence of subsequent chemical hepatitis but did develop a significant Coomb's negative hemolytic anemia. Hemoglobin on presentation was 14 g/dL and reached a nadir of 9.4 g/dL on admission day 4.

CONCLUSION

Patients with glucose-6-phosphate dehydrogenase deficiency who overdose with acetaminophen should be monitored for the possible development of subsequent drug-induced hemolysis.

Paracetamol self-poisoning. Characteristics, prevention and harm reduction

BACKGROUND

Paracetamol is now the most common drug used for self-poisoning in the UK and is associated with potentially fatal liver damage. Patients admitted to hospital because of paracetamol overdoses were studied in order to determine their characteristics and factors which might have deterred them from taking paracetamol or reduced the dangers of the overdose.

METHOD

Eighty patients were studied in hospital using a structured interview schedule, measures of depression and suicidal intent, information collected through the Oxford Monitoring System for Attempted Suicide, and the results of liver function tests.

RESULTS

Acute liver dysfunction (25 patients) was associated with consumption of more than 25 tablets (odds ration 4.46, 95% CI 1.31 to 17.41, P = 0.014). The proportionate use of tablets from blister packs (60%) and loose preparations (46%; 5 patients using both types) reflected their general availability. More of those who took tablets from a loose preparation consumed 25 or more tablets (69%) than those who used a blister-pack preparation (40%; odds ratio = 3.0, 95% CI 1.12 to 9.95, P = 0.028). Only 20 patients thought that any type of warning label would have deterred them from taking a paracetamol overdose.

CONCLUSIONS

Establishing a maximum number of tablets (e.g. 25) that can be available in individual preparations is likely to reduce the dangers of paracetamol self-poisoning. The potential effects of other measures are uncertain.

Management of acetaminophen toxicity

Acetaminophen poisoning is a significant medical problem in the United States and is frequently managed by family physicians. The primary clinical effect of acetaminophen poisoning is hepatotoxicity that occurs after ingestion of large single doses of acetaminophen or after ingestion of smaller doses in patients with hepatic metabolism that is altered by drugs or concurrent medical conditions. Hepatocellular damage is probably caused by accumulation of the toxic intermediate metabolite N-acetyl-p-benzoquinoneimine when hepatic glutathione stores are depleted. Treatment of acetaminophen poisoning consists of preventing gastrointestinal absorption of the drug, use of the antidote N-acetylcysteine and supportive care.

Pharmacokinetics of extended relief vs regular release Tylenol in simulated human overdose

BACKGROUND

The purpose of this trial was to compare the pharmacokinetics of the two available acetaminophen dosage forms in simulated human overdose.

METHODS

Ten healthy volunteers received acetaminophen, 75 mg/kg orally, either as the regular release or extended relief formulation in a random, crossover fashion. Blood samples were analyzed using a TDx assay and a best fit correlation of data points was determined by PCNONLIN.

RESULTS

The area under the curves for extended relief acetaminophen and regular release acetaminophen were 426 mg h/L and 432 mg h/L, respectively (p = 0.768). The mean half times for extended relief acetaminophen and regular release acetaminophen were 4.02 h and 2.56 h, respectively (p < 0.001). The mean maximum serum acetaminophen concentrations were 62.6 mg/L (414.4 mmol/L:) and 94.3 mg/L (624.3 mmol/L) for extended relief acetaminophen and regular release acetaminophen, respectively (p < 0.001) and the mean time to maximum serum acetaminophen concentrations were 0.87 h and 0.75 h for extended relief acetaminophen and regular release acetaminophen, respectively (p = 0.508).

CONCLUSIONS

Although the formulations appear to have equal bioavailability, their half-lives and peak concentrations were significantly different. Further study is required to determine whether these differences affect the assessment and management of poisoned patients.

Media influence on parasuicide. A study of the effects of a television drama portrayal of paracetamol self-poisoning

BACKGROUND

Paracetamol self-poisoning, which carries a significant risk of fatal liver damage, is increasing in the UK, especially among adolescents. There is concern that media portrayal of suicidal behaviour may influence its occurrence. We have investigated the effects of two broadcasts of a television drama showing a teenage girl's overdose of paracetamol.

METHOD

Data from the Oxford Monitoring System for Attempted Suicide were used to examine changes in the number of overdoses and the use of paracetamol in the three week period before and after both broadcasts. An analysis of log-linear models was carried out, using additional data from two previous years, in order to control for the effects of gender, age group, time period, season, year and drug. A questionnaire was used to ascertain whether the programme had influenced patients' decisions to take an overdose or their choice of drug.

RESULTS

An increase in paracetamol overdoses occurred following the first broadcast, but when data from the two previous years were examined and the log-linear analysis was used there was no evidence of significant effects attributable to the broadcasts. The questionnaire study revealed that very few people had seen either episode, and only two claimed that it had influenced them (one in terms of getting help).

CONCLUSIONS

It is important to use sound methodology to avoid interpreting chance fluctuations as a media effect. The potential positive benefits of such programmes should also be investigated.

A 7-year experience of severe acetaminophen-induced hepatotoxicity (1987-1993)

BACKGROUND & AIMS

Five hundred sixty patients admitted between January 1, 1987, and December 31, 1993, with severe acetaminophen-induced hepatotoxicity were studied. The aim of this study was to identify why severe acetaminophen-induced hepatotoxicity still occurs and to determine how known risk factors and advances in management have affected the pattern of illness and outcome.

METHODS

This was a retrospective study of the etiologic factors and the clinical course of all acetaminophen-related admissions.

RESULTS

The number of admissions increased from 58 in 1987 to 123 in 1993. During the corresponding period, overall survival improved from just < 50% to 78%. The percentage of admissions treated with N-acetylcysteine increased from 40% in 1987 to 83% in 1993. The frequency with which grade III or IV encephalopathy developed decreased from 62% in 1987 to 40% in 1993, and the percentage of these patients who developed cerebral edema decreased from 61% to 45% during the same period. There was an increase in both the number of patients transplanted and the survival of those managed medically.

CONCLUSIONS

Severe acetaminophen-induced hepatotoxicity remains a serious condition, but the increasing use of N-acetylcysteine, advances in medical management, and the increasing availability of transplantation have resulted in a significant improvement in survival rates.