Delayed toxidromes.

Some toxins do not result in clinical manifestations until several hours after exposure. This article reviews those agents that may cause delayed-onset toxicity. They are organized into four classes: specific pharmaceuticals, biologicals, pharmaceutical dosage forms, and chemicals. There are five basic mechanisms for delayed toxicity: delayed absorption, distribution factors, metabolic factors, cellular and organ capacity effects, and unknown. Scientific evidence for delayed-onset of effects varies considerably among the individual toxins.

Arrhythmias after astemizole overdose.

Astemizole, a relatively new H1 blocker, has been reported to cause ventricular arrhythmias in the poisoned patient. We present two cases of astemizole poisoning, one with asystole followed by ventricular fibrillation occurring 11 hours after ingestion treated with defibrillation and one with an isolated finding of a prolonged corrected QT interval. Electrocardiogram monitoring to detect conduction defects can identify patients at risk of developing life-threatening arrhythmias.

Does the histamine skin prick test identify patients at risk for toxicity after the ingestion of astemizole?

Astemizole is a widely prescribed nonsedating antihistamine that suppresses wheal and flare reactions from histamine prick testing. We report a two-year-old girl with a serum concentration-proven overdose of astemizole who nonetheless exhibited a significant wheal and flare reaction after histamine skin prick testing for at least 22 hours after the ingestion. These findings suggest that histamine skin prick testing should not be used as a screening test to evaluate whether an ingestion of astemizole has occurred.

Special considerations in the poisoned pediatric patient.

The incidence of serious pediatric morbidity and mortality has fortunately declined over the past two decades due to better prevention efforts, the development of regionalized poison information programs, and advances in the emergency management and critical care of poisoned patients. Still, children continue to explore and often ingest many substances they discover in their world. Some of these children will become patients who present to the emergency department, requiring a coordinated approach to the seriously or even critically ill poisoned child by physicians who can access specialized resources to manage a vast spectrum of potential toxins. This article summarized one such approach, emphasizing initial attention to life support priorities, followed by a detailed evaluation process using readily available clinical and laboratory data. Management strategies including decontamination, urgent antidotal therapy, initiation of excretion enhancement, and optimal supportive care were reviewed. Several specific intoxications were illustrated briefly in an attempt to facilitate pattern recognition of characteristic pediatric exposures.

Torsade de pointes associated with Astemizole overdose treated with magnesium sulfate.

Astemizole (Hismanal-Janssen, New Brunswick, NJ) is a nonsedating antihistamine that has the advantage of a once-daily dosage schedule. This article reports the case of a 14-year-old female who intentionally ingested 270 mg of Astemizole and developed torsade de pointes, a form of polymorphic ventricular tachycardia that is associated with prolongation of the QTc interval. She was successfully treated with magnesium sulfate infusion and had an uneventful recovery over a period of 36 hours. This case illustrates that Astemizole overdose is not benign and should be considered in the differential diagnosis of ventricular tachyarrhythmias. Use of high-dose Astemizole may not be advisable for patients who are at risk for prolongation of the QTc interval.

Prolonged QT interval and torsade de pointes following astemizole overdose.

A 26 year-old woman was admitted to the hospital two hours after astemizole overdose. Electrocardiograph showed a prolonged QT interval. Torsade de pointes occurred 13 h after ingestion. Plasma levels of astemizole plus hydroxylated metabolites showed an apparent plasma half-life of 17 h. The possible occurrence of torsade de pointes in astemizole overdose, and the long elimination time of astemizole and hydroxylated metabolites, makes it necessary to maintain ECG monitoring until QT interval has returned to normal.

Cardiotoxic effects of astemizole overdose in children.

Astemizole, a nonsedating antihistamine, caused a prolonged corrected QT interval, ventricular dysrhythmias, and atrioventricular heart block after overdose in five children. Cardiotoxic effects lasted an average of 2 1/2 days. Children poisoned with astemizole need emergent medical evaluation, a 12-lead electrocardiogram with calculation of the corrected QT interval, and continuous cardiac monitoring for 24 hours.

Astemizole-induced cardiac conduction disturbances in a child.

The newly available antihistamine astemizole (Hismanal) has been previously associated with hemodynamically significant cardiac tachydysrhythmias. We describe a 3-year-old girl who developed multiple different cardiac dysrhythmias after an astemizole overdose. No hemodynamic compromise occurred, and the electrocardiogram returned to normal without use of antiarrhythmic agents within 7 hours.

Astemizole-induced ventricular arrhythmias: an unexpected cause of convulsions.

Antihistamines are commonly used drugs. The more recent additions to the formulary are less sedative, but have been implicated as a cause of ventricular arrhythmias. We report a case in which a deliberate overdose of astemizole was associated with Mobitz type two heart block and prolongation of the QT interval, causing the so-called torsade-de-pointes ventricular tachycardia.