Updated: Nov 6, 2008
Digitalis is a cardiac glycoside with many important therapeutic considerations. Although these concerns are predominant in the adult population, acute digitalis poisoning in the pediatric population is well described in the literature. Despite improved pharmacologic knowledge, digitalis poisoning continues to be a serious problem in infants and children because of its wide availability and narrow therapeutic index. The availability of digoxin-specific fragment antigen binding (Fab) antibody fragments has considerably improved the outlook of patients with severe forms of digitalis poisoning.
Digoxin is the most widely used cardiac glycoside and the only digitalis preparation in common therapeutic use in the United States. In 1980, digoxin was the eighth most widely prescribed drug in the United States; many recent surveys list it among the top 10 drugs prescribed in office practice. Digitalislike compounds are also found in certain plants such as the common oleander, foxglove, yew berry, dogbane, lily of the valley, and red squill, as well as in certain toad species. Herbal exposure usually occurs through the ingestion of plants or the inhalation of smoke from burning plants. Cardiac glycoside toxicity accounts for 2.6% of reported cases of toxicity due to plant ingestion.
Digitalis inhibits the active transport of sodium and potassium across cell membranes by binding to a specific site on the extracytoplasmic surface of the alpha subunit of the sodium-activated and potassium-activated adenosine triphosphatase (NaK ATPase) pump; this binding is a reversible process. The net result is an increase in the intracellular sodium and calcium concentrations and a decrease in the intracellular potassium concentration. Digitalis increases phase 4 of the action potential in most myocardial tissue, leading to a reduction of conduction velocity with increased automaticity and ectopic activity. Improved inotropy is due to an increased concentration of cytosolic calcium ions during systole. Digitalis also has a negative chronotropic action, which is partly a vagal effect and partly a direct effect on the sinoatrial (SA) node.
The therapeutic daily dose of digoxin ranges from about 0.005 mg/kg in premature infants to as much as 0.75 mg in adults. The absorption of digoxin tablets is 70-80%; its bioavailability is 95%. The kidney excretes 60-80% of the digoxin dose unchanged. The onset of action by oral (PO) administration occurs in 30-120 minutes; the onset of action with intravenous (IV) administration occurs in 5-30 minutes. The peak effect with PO dosing is 2-6 hours, and that with IV dosing is 5-30 hours. Only 1% of the total amount of digoxin in the body is in the serum; of that amount, approximately 25% is protein bound.
The volume of distribution is 6-10 L/kg in adults, 10 L/kg in neonates, and as much as 16 L/kg in infants and toddlers. At therapeutic levels, the elimination half-life is 36 hours with renal excretion. In acute digoxin intoxication in toddlers and children, the average plasma half-life is 11 hours. With acute intoxication, plasma concentrations extrapolated to time zero is lower in toddlers than in infants and older children because of their increased volume of distribution and clearance.
The lethal dose of digoxin is considered to be 20-50 times the maintenance dose taken at once. In healthy adults, a does of less than 5 mg seldom causes severe toxicity, but a does of more than 10 mg is almost always fatal. In the pediatric population, the ingestion of more than 4 mg or 0.3 mg/kg portends serious toxicity.
The prevalence of digitalis toxicity in the pediatric population are difficult to establish. As many as 15% of hospitalized adults are receiving digoxin therapy, and the prevalence of digoxin toxicity is as high as 30%. In 1985, the American Association of Poison Control Centers (AAPCC) National Data Collection System (Toxic Exposure Surveillance System) reported 1015 cases of cardiac glycoside overdose, of which 584 involved children younger than 6 years, and 56 involved children aged 6-17 years.1 Of all adult and pediatric patients, 842 cases (83%) were nonintentional.
Overall mortality rates vary among different pediatric studies; rates of 10-24% were reported before the introduction of digoxin-specific Fab antibody fragments. The overall mortality rate and rate of response to Fab therapy in children are similar to those in adults. The mortality rate as a direct result of cardiac toxicity is 3-21%.
The incidence of digitalis poisoning is higher in males than in females; males also have a higher mortality rate.
Manifestations of digitalis toxicity vary depending on age; populations at the extremes of age are most susceptible. For instance, ventricular ectopy is most prevalent in older patients; conduction defects and supraventricular ectopic rhythms are most prevalent in younger patients.
Most cases of cardiac glycoside toxicity related to plant ingestion occur in children younger than 6 years. Of the 1015 cases of cardiac glycoside overdose reported by the AAPCC in 1985, 584 involved children younger than 6 years, and 56 involved children aged 6-17 years.1 In 80% of reported cases of digitalis toxicity in toddlers, children had found and ingested their grandparents' medications.
Most cases of pediatric digitalis poisoning are unintentional ingestions; thus, a good social history with emphasis on available medications and the extent of home childproofing is necessary.
Patients can have an asymptomatic period of several minutes to several hours after the oral administration of a single toxic dose. Clinical signs may be subtle or obvious, depending on the severity of toxicity. Acute toxicity is rarely subtle, and chronic toxicity may be difficult to diagnose. CNS changes, most notably nausea, vomiting, and drowsiness are the most common extracardiac manifestations. Visual changes usually affect patients with chronic toxicity.
Emphasis should be placed on the vital signs and the neurologic and cardiovascular findings.
| Atrioventricular Block, Second Degree | Sepsis |
| Gastroenteritis | Sinus Node Dysfunction |
| Hypoglycemia | Toxicity, Calcium Channel Blocker |
| Meningitis, Aseptic | Toxicity, Organophosphates |
| Meningitis, Bacterial |
Cardiotoxic plant ingestion
Class I-A cardiac drug toxicity
Clonidine toxicity
Laboratory studies in patients with digitalis toxicity are as follows:
General supportive care of digitalis toxicity includes hydration with intravenous (IV) fluids, oxygenation and support of ventilatory function, and correction of electrolyte imbalances.
Most authors recommend potassium supplementation if potassium levels are less than 4 mmol/L. Forced diuresis is not recommended because it has not been shown to increase renal excretion and can worsen electrolyte abnormalities. Dialysis has been shown to produce only small-added clearances.
Digoxin-specific fragment antigen binding (Fab) antibody fragments are extremely effective in the treatment of severe acute digitalis toxicity.
Since the introduction of purified digoxin-specific Fab antibody fragments in 1976, the outcome in severe acute digitalis poisoning has been drastically improved. Other supportive medications include phenytoin or lidocaine for arrhythmias, atropine, and magnesium.
This agent is used in the management of poisoning, overdoses, prevention of toxic effects, and metabolic disorders in which toxic substances accrue. In cases of digitalis toxicity, specific antidigoxin antibodies are used to treat hemodynamically unstable or life-threatening arrhythmias and hyperkalemia.
50,000-Da molecule derived from IgG fragment of sheep antidigoxin antibodies. This relatively pure Fab product is safe and extremely effective. Indications for use include life-threatening arrhythmias (eg, severe bradyarrhythmia, second- or third-degree heart block, ventricular tachycardia or fibrillation), initial potassium level >5 mmol/L, digoxin serum levels >10 ng/mL at 6-8 h after ingestion, digoxin serum levels >15 ng/mL in acute ingestion, and ingestion >10 mg in healthy adults or >4 mg in children.
Binds free digoxin in vascular and interstitial space and decreases free plasma digoxin levels by binding intracellular digoxin from its binding sites in heart and interstitial and intravascular spaces. Raises intravascular levels of inactive antibody-bound digoxin to very high levels, which decrease over several days as it is excreted renally. Response typically observed within 20-30 min; elimination half-life of drug-antibody complex is about 16 h.
Affinity for digitoxin is 10 times less than for digoxin. In recent case series including pediatric patients, 90-93% response rate within minutes or hours, with complete resolution within 180 min in as many as 79% of patients. Mean time to initial response was 19 min; complete resolution of symptoms in 88 min. Each vial contains 40 mg Fab and binds 0.6 mg of digoxin.
If amount ingested or infused known: Number of vials = (mg ingested) X 0.8/0.6
If serum digoxin level known: Number of vials = [serum level (ng/mL) X 5.6 X body weight (kg)/1000]/0.6
Empiric dosing: 10-20 vials in acute ingestion, 2-6 vials in chronic ingestion; mix each vial with 4 mL 0.9% NaCl and administer through 0.22 µm membrane filter; administer IV over 30 min; can administer as IV bolus if unstable; may need additional dose
Administer as in adults
Empiric dose: 5-20 vials in acute ingestion; for chronic ingestion, use 1/4 to 1/2 the number of vials
None reported
Documented hypersensitivity; renal or cardiac failure
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Observe for hypokalemia and congestive heart failure in patients with digoxin dependency; transient hypoglycemia 13 h after administration reported in a neonate; only mild acute hypersensitivity reactions (eg, rash, flushing, facial swelling) reported; infants and children may experience a febrile reaction
These agents alter the electrophysiologic mechanisms responsible for arrhythmia. These are used as an alternative to digoxin immune Fab.
Anticholinergic agent used to increase heart rate by means of vagolytic effects, increasing cardiac output.
0.5-1 mg IV; can repeat q3-5min; not to exceed cumulative dose of 3 mg
0.02 mg/kg IV; minimum dose 0.1 mg; can repeat q3-5min; not to exceed cumulative dose of 1 mg
Coadministration with other anticholinergics have additive effects; may increase pharmacologic effects of atenolol and digoxin; may decrease antipsychotic effects of phenothiazines; tricyclic antidepressants with anticholinergic activity may increase effects
Documented hypersensitivity; narrow-angle glaucoma; tachycardia; thyrotoxicosis; obstructive disease of GI tract; obstructive uropathy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Avoid in Down syndrome and/or children with brain damage to prevent hyperreactive response; avoid in coronary heart disease, tachycardia, congestive heart failure, cardiac arrhythmias, and hypertension; caution in peritonitis, ulcerative colitis, hepatic disease, and hiatal hernia with reflux esophagitis; in prostatic hypertrophy, prostatism can cause dysuria (may require catheterization)
Depresses spontaneous depolarization in ventricular tissues.
15-20 mg/kg IV infusion, rate <50 mg/min
Administer as in adults
Amiodarone, benzodiazepines, chloramphenicol, cimetidine, fluconazole, isoniazid, metronidazole, miconazole, phenylbutazone, succinimides, sulfonamides, omeprazole, phenacemide, disulfiram, ethanol (acute ingestion), trimethoprim, and valproic acid may increase toxicity; concurrent barbiturates, diazoxide, ethanol (chronic ingestion), rifampin, antacids, charcoal, carbamazepine, theophylline, and sucralfate may decrease effects; may decrease effects of acetaminophen, corticosteroids, dicumarol, disopyramide, doxycycline, estrogens, haloperidol, amiodarone, carbamazepine, cardiac glycosides, quinidine, theophylline, methadone, metyrapone, mexiletine, oral contraceptives, and valproic acid
Documented hypersensitivity; SA block, second- or third-degree AV block, sinus bradycardia, or Adams-Stokes syndrome
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Discontinue if rash appears (do not resume use if rash is exfoliative, bullous, or purpuric); rapid IV infusion may cause death from cardiac arrest marked by QRS widening; caution in acute intermittent porphyria and diabetes mellitus (may elevate blood sugar levels; discontinue if hepatic dysfunction occurs
Class IB antiarrhythmic that increases electrical stimulation threshold of ventricle, suppressing automaticity of conduction through the tissue.
Loading dose: 1-1.5 mg/kg IV; can repeat in 5 min; not to exceed a cumulative dose of 3 mg/kg/dose
Maintenance: 1-4 mg/min IV continuous infusion
Loading dose: 1-1.5 mg/kg IV; can repeat in 5 min; not to exceed a cumulative dose of 3 mg/kg
Maintenance: 20-50 mcg/kg/min IV continuous infusion
Coadministration with cimetidine or beta-blockers increases toxicity; coadministration with procainamide and tocainide may result in additive cardiodepressant action; may increase effects of succinylcholine
Documented hypersensitivity to amide-type local anesthetics; Adams-Stokes syndrome and Wolff-Parkinson-White syndrome; severe SA, AV, or intraventricular block if artificial pacemaker not in place
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Use a solution without preservatives; caution in heart failure, hepatic disease, hypoxia, hypovolemia or shock, respiratory-depression, and bradycardia; may increase risk of CNS and cardiac adverse effects; high plasma concentrations can cause seizures, heart block, and AV conduction abnormalities
Litovitz TL, Normann SA, Veltri JC. 1985 Annual Report of the American Association of Poison Control Centers National Data Collection System. Am J Emerg Med. Sep 1986;4(5):427-58. [Medline].
Smith TW, Butler VP Jr, Haber E, et al. Treatment of life-threatening digitalis intoxication with digoxin- specific Fab antibody fragments: experience in 26 cases. N Engl J Med. Nov 25 1982;307(22):1357-62. [Medline].
Woolf AD, Wenger T, Smith TW, Lovejoy FH Jr. The use of digoxin-specific Fab fragments for severe digitalis intoxication in children. N Engl J Med. Jun 25 1992;326(26):1739-44. [Medline].
Zucker AR, Lacina SJ, DasGupta DS, et al. Fab fragments of digoxin-specific antibodies used to reverse ventricular fibrillation induced by digoxin ingestion in a child. Pediatrics. Sep 1982;70(3):468-71. [Medline].
Antman EM, Wenger TL, Butler VP Jr, et al. Treatment of 150 cases of life-threatening digitalis intoxication with digoxin-specific Fab antibody fragments. Final report of a multicenter study. Circulation. Jun 1990;81(6):1744-52. [Medline].
Beller GA, Smith TW, Abelmann WH, et al. Digitalis intoxication. A prospective clinical study with serum level correlations. N Engl J Med. May 6 1971;284(18):989-97. [Medline].
Bismuth C, Gaultier M, Conso F, Efthymiou ML. Hyperkalemia in acute digitalis poisoning: prognostic significance and therapeutic implications. Clin Toxicol. 1973;6(2):153-62. [Medline].
Ekins BR, Watanabe AS. Acute digoxin poisonings: review of therapy. Am J Hosp Pharm. Mar 1978;35(3):268-77. [Medline].
Fazio A. Fab fragments in the treatment of digoxin overdose: pediatric considerations. South Med J. Dec 1987;80(12):1553-6. [Medline].
Hastreiter AR, van der Horst RL, Chow-Tung E. Digitalis toxicity in infants and children. Pediatr Cardiol. Apr-Jun 1984;5(2):131-48. [Medline].
Husby P, Farstad M, Brock-Utne JG, et al. Immediate control of life-threatening digoxin intoxication in a child by use of digoxin-specific antibody fragments (Fab). Paediatr Anaesth. Jul 2003;13(6):541-9. [Medline].
Kaufman J, Leikin J, Kendzierski D, Polin K. Use of digoxin Fab immune fragments in a seven-day-old infant. Pediatr Emerg Care. Jun 1990;6(2):118-21. [Medline].
Lewander WJ, Gaudreault P, Einhorn A, et al. Acute pediatric digoxin ingestion. A ten-year experience. Am J Dis Child. Aug 1986;140(8):770-3. [Medline].
Ordog GJ, Benaron S, Bhasin V, et al. Serum digoxin levels and mortality in 5,100 patients. Ann Emerg Med. Jan 1987;16(1):32-9. [Medline].
Rutledge J. Digitalis toxicity in infants and plasma digoxin levels. Pediatr Cardiol. 1985;6(1):51-2. [Medline].
Shumaik GM, Wu AW, Ping AC. Oleander poisoning: treatment with digoxin-specific Fab antibody fragments. Ann Emerg Med. Jul 1988;17(7):732-5. [Medline].
Aarnoudse AL, Dieleman JP, Stricker BH. Age- and gender-specific incidence of hospitalisation for digoxin intoxication. Drug Saf. 2007;30(5):431-6. [Medline].
digitalis toxicity, digitalis poisoning, acute digitalis poisoning, digoxin, digoxin poisoning, digoxin intoxication, cardiac glycosides, cardiac glycoside toxicity, Digitalis purpurea, headache, seizures, diarrhea, chromatopsia, xanthopsia, amblyopia, scotomata, decreased visual acuity, hyperkalemia, hypokalemia, hypomagnesemia, hypercalcemia, quinidine, procainamide, amiodarone, calcium channel blockers, beta-blockers, diuretics, hypothyroidism
Kenneth T Kwon, MD, Director of Pediatric Emergency Medicine, Associate Clinical Professor, Department of Emergency Medicine, University of California at Irvine Medical Center
Kenneth T Kwon, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.
William T Zempsky, MD, Associate Director, Assistant Professor, Department of Pediatrics, Division of Pediatric Emergency Medicine, University of Connecticut and Connecticut Children's Medical Center
William T Zempsky, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.
Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation
Jeffrey R Tucker, MD, Assistant Professor, Department of Pediatrics, Division of Emergency Medicine, University of Connecticut and Connecticut Children's Medical Center
Jeffrey R Tucker, MD is a member of the following medical societies: American Academy of Clinical Toxicology, American Academy of Pediatrics, and Massachusetts Medical Society
Disclosure: Merck Salary Employment
Paul D Petry, DO, FACOP, FAAP, Consulting Staff, Freeman Pediatric Care, Freeman Health System
Paul D Petry, DO, FACOP, FAAP is a member of the following medical societies: American Academy of Osteopathy, American Academy of Pediatrics, American College of Osteopathic Pediatricians, and American Osteopathic Association
Disclosure: Nothing to disclose.
Timothy E Corden, MD, Associate Professor of Pediatrics, Co-Director, Policy Core, Injury Research Center, Medical College of Wisconsin; Associate Director, PICU, Children's Hospital of Wisconsin
Timothy E Corden, MD is a member of the following medical societies: American Academy of Pediatrics, Phi Beta Kappa, Society of Critical Care Medicine, and Wisconsin Medical Society
Disclosure: Nothing to disclose.
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