Severe digoxin intoxication in a child treated by infusion of digoxin-specific Fab-antibody-fragments

Frequency, etiology and several sociodemographic characteristics of acute poisoning in children treated in the intensive care unit

AIM

The aim of this work has been to present the frequency, etiology and several other socio-demographic characteristics of acute poisoning in children. THE TREATED PATIENTS AND METHODS OF WORK: The treated patients were children of all age groups hospitalized in the Pediatric Clinic of Prishtina during year 2009. The study was done retrospectively. The diagnosis was done on the basis of heteroanamnesis and in several cases on the basis of the anamnesis data of a child, routine laboratory tests and toxicologic analysis.

RESULTS

66 (9.4%) poisoned children were treated in the Intensive Care Unit. The biggest number of patients, 37 (56.06%) of them, were male, and out of that number 36 (54.55%) cases were coming from rural areas. The biggest number of them 49 (74.98%) were over 2-6 years old. The poisoning was mostly caused through the digestive tract (ingestion), it happened with 55 cases (83.33%), 56 cases (84,80%) suffered from severe poisoning, whereas 59 cases (89,50%) suffered from accidental poisoning. Regarding the type of the substances that caused poisoning, the most frequent were drugs in 34 (51.50%) cases and pesticides in 20 (30.30%) cases. Among drugs, the most dominant were those belonging to a group of benzodiazepines (10 cases) and metoclopramide (4 cases). Among pesticides the most dominant one that caused poisoning was malation (5 cases), then paration and cipermetrina appeared in 3 cases each. The biggest number of cases, 64 (96.96%) of them, were treated, whereas 2 cases (3.40%) passed away.

CONCLUSION

The practice proved that that our people are not well informed about the poisoning in general, therefore it is necessary that they be educated by the use of all media, written and electronic, as well as other methods of medical education.

The use of digoxin-specific Fab fragments for severe digitalis intoxication in children

BACKGROUND

Because life-threatening digitalis intoxication is unusual in children, treatment with digoxin-specific-antibody Fab fragments (Fab) has rarely been reported. We describe the efficacy of Fab in the treatment of children with severe digitalis intoxication.

METHODS

Twenty-nine children with intoxication due to digoxin (28) or digitoxin (1) received Fab at 21 participating hospitals between 1974 and 1986. Data were gathered about the patients' medical illnesses, doses and serum concentrations of digitalis, responses to Fab therapy, and outcomes.

RESULTS

In the infants and young children with acute digoxin intoxication, the digoxin doses ranged from 0.30 to 0.96 mg per kilogram of body weight; two adolescents had severe intoxication after doses of only 0.20 and 0.26 mg per kilogram. The serum digoxin concentrations ranged from 3.0 to greater than 100 ng per milliliter (mean, 13.8). Atrioventricular block (present in 22 patients [76 percent]) was the most common sign of toxicity. All the patients in this series had severe disturbances of cardiac rhythm, hyperkalemia (mean serum potassium concentration, 5.4 mmol per liter), or both. In 27 patients (93 percent), digitalis toxicity resolved after the administration of Fab. Of the 19 patients for whom data were available on the timing of the response to Fab, 15 responded within 180 minutes. Three patients required retreatment with Fab. Seven died of complications unrelated to the administration of Fab.

CONCLUSIONS

We recommend that Fab be used in the treatment of digitalis poisoning in infants and young children who have ingested greater than or equal to 0.3 mg of digoxin per kilogram, who have underlying heart disease, or who have a serum digoxin concentration of greater than or equal to 6.4 nmol per liter (greater than or equal to 5.0 ng per milliliter) in the elimination phase; and who also have a life-threatening arrhythmia, hemodynamic instability, hyperkalemia, or rapidly progressive toxicity. Adolescents, who are more sensitive to the toxic effects of digoxin than younger children, may require treatment with Fab after ingesting lower doses.

Age-related differences in digoxin toxicity and its treatment

Digoxin toxicity remains a common medical problem for both adults and children. In addition to a vastly improved understanding of the mechanisms for digoxin action on the heart, there are now data which clearly demonstrate that there are potentially important developmental differences in both the pharmacodynamics and pharmacokinetics of digoxin which have a direct impact on its efficacy and toxicity profile. The developmental pharmacokinetics of the drug have been extensively studied such that profiles for age-dependent differences in the apparent volume of distribution, plasma and renal clearance and elimination half-life now exist. It is these data which have also produced the current age-specific dosing guidelines for the therapeutic administration of digoxin in various paediatric subpopulations. Despite this new knowledge, both accidental and iatrogenic digoxin toxicity still occurs in paediatric patients, with potentially life-threatening arrhythmias being produced when steady-state serum digoxin concentrations exceed 5.1 nmol/L. Consequently, the clinician may be faced with the decision to use antidotal therapy with digoxin-specific Fab fragments (d-Fab). This article reviews the developmental basis for digoxin disposition and its pharmacological and toxic effects. Additionally, the treatment of acute digoxin toxicity in children is reviewed, especially as pertains to the therapeutic use of d-Fab.

Results of multicenter studies of digoxin-specific antibody fragments in managing digitalis intoxication in the pediatric population

Digitalis toxicity continues to be a problem for pediatric patients undergoing therapy with cardiac glycosides for heart failure or arrhythmias, as well as in accidental ingestions. In this article the previous use of digoxin-specific antibody Fab fragments to treat digitalis overdose or intoxication in children is reviewed. The case reports cited in the medical literature and the 57 pediatric cases gathered as a result of the multicenter clinical trial and postmarketing surveillance study reported here indicate that digoxin-specific antibody Fab fragments are effective in ameliorating signs of digitalis poisoning in children. Not only can Fab fragments rapidly eradicate potentially life-threatening arrhythmias and conduction defects, but they are also effective in treating hyperkalemia and other noncardiac manifestations of digitalis toxicity. In the small samples of patients studied to date, complications have been minimal and no allergic reactions to digoxin-specific Fab fragments have been observed. Recommendations for the management of digitalis intoxication in children are outlined.

Pharmacokinetics and efficacy of digoxin specific Fab fragments in a child following massive digoxin overdose

The use of digoxin-specific Fab fragments (d-Fab) to treat life-threatening digitalis intoxication has been widely substantiated in adults. This reports a case of a 2-year-old girl who ingested 90-92, 0.25 mg tablets of digoxin and within four hours, developed vomiting, lethargy, tachycardia and AV block (Mobitz type I and II). These symptoms were associated with total and free serum digoxin concentrations of 17.1 and 12.4 ng/ml, respectively. Following GI decontamination, a total dFab dose of 1280 mg (32 vials) was given with resolution of electrocardiographic abnormalities within 40 minutes and a concomitant reduction in the free serum digoxin concentration to 0.11 ng/ml. Repeated blood sampling over 19 days revealed an apparent elimination half-life (t1/2) of 134.9 and 129.9 hr for total and free digoxin, respectively. The long t1/2 for digoxin corresponded to a low apparent renal clearance of total digoxin which ranged from 0.56 to 0.82 ml/minute over four separate collection intervals. The free serum digoxin concentration never exceeded 3% of the total concentration and the patient did not develop a recurrence of toxic symptoms or any adverse effects (e.g. fever) attributable to dFab. Administration of an equimolar dFab dose to children following acute, massive digoxin intoxication represents safe, effective treatment which produces a prompt, sustained reversal of toxic effects. Digoxin specific Fab fragments should be promptly administered to any infant or child with significant, life-threatening symptoms following acute digoxin intoxication.

Delayed elimination of digoxin antidotum determined by radioimmunoassay

An observation of a treatment with digitalis antibodies (Fab-fragments) in a young child is presented. The elimination of this antidotum proved to be much slower than normally expected. In the patient's history, the disappearance of the Fab-fragments out of the blood lasted 142 days with a half-life of 15.6 days, whereas an elimination with a T1/2 of 28 hours is accepted. Probably there has been intracellular penetration of the antibodies into the liver, caused by concomitant diseases (Hepatitis A and B infections). An "in vitro" experiment is reported. It demonstrates the equimolar binding of the Fab-fragments for digoxin and shows that the elimination of the Fab-fragments can be established by a routine radioimmunoassay of digoxin, in an indirect way.

Antibodies and digitalis: the modern revolution in the use of an ancient drug

Although digitalis glycosides have been widely used in clinical medicine since the classic description by William Withering in 1785, it was not until the advent of a specific immunoassay that their clinical pharmacology could be examined intensively under a wide variety of circumstances. The insights gained into the relations among dosage, plasma concentration, bioavailability, distribution, metabolism, excretion and interactions with other drugs and the manifestations of toxicity certainly have reduced the frequency of adverse reactions to this highly toxic but useful group of drugs. More recently, antibodies have also been utilized as specific antidotes for digitalis toxicity, with dramatic life-saving effect.

Digoxin specific antibody (Fab) fragments in 34 cases of severe digitalis intoxication

34 patients aged between 2 and 80 years were treated with digoxin specific antibody (Fab) fragments for severe digitalis poisoning. In 27 cases, the glycoside was taken with suicidal intent; in 3 cases accidentally and 4 were iatrogenic. The following criteria were considered to be indications for use of Fab fragments: the appearance of life-threatening arrhythmias such as high-grade atrioventricular conduction disorders (grade 2 and 3 A-V block), multifocal ectopic beats, ventricular tachycardia, and relapsing ventricular fibrillation. Serum digoxin concentrations were between 3.4 and 29ng/ml before the start of treatment. Between 240 and 800mg of Fab were administered; the majority of patients received 480mg. Regression of arrhythmias was seen between 0.5 and 8 hours after Fab infusion. There was a rapid fall in the free digoxin in the serum to concentrations that were no longer measurable and a marked rise in bound digoxin with a simultaneous increase of excretion of bound digoxin in the urine. Fab therapy is considered to be a major advance in the treatment of severe, previously fatal, glycoside poisoning. No notable side effects or allergic reactions were observed.