Severe clonidine overdose in children requiring critical care

Overdose of drugs for attention-deficit hyperactivity disorder: clinical presentation, mechanisms of toxicity, and management

The prevalence of attention-deficit hyperactivity disorder (ADHD) in the USA is estimated at approximately 4-9% in children and 4% in adults. It is estimated that prescriptions for ADHD medications are written for more than 2.7 million children per year. In 2010, US poison centers reported 17,000 human exposures to ADHD medications, with 80% occurring in children <19 years old and 20% in adults. The drugs used for the treatment of ADHD are diverse but can be roughly separated into two groups: the stimulants such as amphetamine, methylphenidate, and modafinil; and the non-stimulants such as atomoxetine, guanfacine, and clonidine. This review focuses on mechanisms of toxicity after overdose with ADHD medications, clinical effects from overdose, and management. Amphetamine, dextroamphetamine, and methylphenidate act as substrates for the cellular monoamine transporter, especially the dopamine transporter (DAT) and less so the norepinephrine (NET) and serotonin transporter. The mechanism of toxicity is primarily related to excessive extracellular dopamine, norepinephrine, and serotonin. The primary clinical syndrome involves prominent neurological and cardiovascular effects, but secondary complications can involve renal, muscle, pulmonary, and gastrointestinal (GI) effects. In overdose, the patient may present with mydriasis, tremor, agitation, hyperreflexia, combative behavior, confusion, hallucinations, delirium, anxiety, paranoia, movement disorders, and seizures. The management of amphetamine, dextroamphetamine, and methylphenidate overdose is largely supportive, with a focus on interruption of the sympathomimetic syndrome with judicious use of benzodiazepines. In cases where agitation, delirium, and movement disorders are unresponsive to benzodiazepines, second-line therapies include antipsychotics such as ziprasidone or haloperidol, central alpha-adrenoreceptor agonists such as dexmedetomidine, or propofol. Modafinil is not US FDA approved for treatment of ADHD; however, it has been shown to improve ADHD signs and symptoms and has been used as an off-label pharmaceutical for this diagnosis in both adults and children. The mechanism of action of modafinil is complex and not fully understood. It is known to cause an increase in extracellular concentrations of dopamine, norepinephrine, and serotonin in the neocortex. Overdose with modafinil is generally of moderate severity, with reported ingestions of doses up to 8 g. The most common neurological effects include increased anxiety, agitation, headache, dizziness, insomnia, tremors, and dystonia. The management of modafinil overdose is largely supportive, with a focus on sedation, and control of dyskinesias and blood pressure. Atomoxetine is a selective presynaptic norepinephrine transporter inhibitor. The clinical presentation after overdose with atomoxetine has generally been mild. The primary effects have been drowsiness, agitation, hyperactivity, GI upset, tremor, hyperreflexia, tachycardia hypertension, and seizure. The management of atomoxetine overdose is largely supportive, with a focus on sedation, and control of dyskinesias and seizures. Clonidine is a synthetic imidazole derivative with both central and peripheral alpha-adrenergic agonist actions. The primary clinical syndrome involves prominent neurological and cardiovascular effects, with the most commonly reported features of depressed sensorium, bradycardia, and hypotension. While clonidine is an anti-hypertensive medication, a paradoxical hypertension may occur early with overdose. The clinical syndrome after overdose of guanfacine may be mixed depending on central or peripheral alpha-adrenoreceptor effects. Initial clinical effects may be drowsiness, lethargy, dry mouth, and diaphoresis. Cardiovascular effects may depend on time post-ingestion and may present as hypotension or hypertension. The management of guanfacine overdose is largely supportive, with a focus on support of blood pressure. Overdose with ADHD medications can produce major morbidity, with many cases requiring intensive care medicine and prolonged hospital stays. However, fatalities are rare with appropriate care.

Toxic clonidine ingestion in children

OBJECTIVES

We performed a prospective case series to seek dosage or clinical parameters to better identify patients who need direct medical evaluation.

STUDY DESIGN

All clonidine ingestions in children younger than 12 years of age reported to 6 poison centers were followed for a minimum of 24 hours. Exclusion criterion was polydrug ingestion.

RESULTS

The study included 113 patients, of whom 63 were male. Mean age was 3.8 years (+/-2.4 SD). Clinical effects were common, but severe adverse effects occurred in <10% of patients. The dose ingested was reported for 90 patients (80%); 61 (68%) children ingested <0.3 mg and none had coma, respiratory depression, or hypotension. The lowest dose ingested by history with coma and respiratory depression was 0.3 mg (0.015 mg/kg). Prior clonidine therapy did not affect outcome. Onset of full clinical effects in all cases was complete within 4 hours of ingestion.

CONCLUSIONS

We recommend direct medical evaluation for (1) all children 4 years of age and younger with unintentional clonidine ingestion of >or=0.1 mg, (2) ingestion of >0.2 mg in children 5 to 8 years of age, and (3) ingestion of >or=0.4 mg in children older than 8 years of age. Observation for 4 hours may be sufficient to detect patients who will develop severe effects.

Deadly pediatric poisons: nine common agents that kill at low doses

More than 97% of pediatric exposures reported to the AAPCC in 2001 had either no effect or mild clinical effects. Despite the large number of exposures, only 26 of the 1074 reported fatalities occurred in children younger than age 6. These findings reflect the fact that, in contrast to adolescent or adult ingestions, pediatric ingestions are unintentional events secondary to development of exploration behaviors and the tendency to place objects in the mouth. Ingested substances typically are nontoxic or ingested in such small quantities that toxicity would not be expected. As a result, it commonly is believed that ingestion of one or two tablets by a toddler is a benign act and not expected to produce any consequential toxicity. Select agents have the potential to produce profound toxicity and death, however, despite the ingestion of only one or two tablets or sips. Although proven antidotes are a valuable resource, their value is diminished if risk after ingestion is not adequately appreciated and assessed. Future research into low-dose, high-risk exposures should be directed toward further clarification of risk, improvements in overall management strategies,and, perhaps most importantly, prevention of toxic exposure through parental education and appropriate safety legislation.

Clonidine toxicity revisited

The incidence of clonidine overdose is increasing, yet there is a paucity of new information regarding treatment options for clonidine toxicity. Reported treatment approaches vary widely, demonstrating the lack of science on which current treatment is based. Available research needs to be reassessed. Neurotransmitters, receptors, endogenous opioids, and baseline sympathetic tone determine the clinical response to clonidine as well as the potential response to drug therapy following clonidine overdose. This article reviews aspects of clonidine toxicity that need to be further investigated. Multicenter research trials will be required to evaluate new treatment options.

Clonidine overdose in childhood: implications of increased prescribing

OBJECTIVE

To highlight the increase in the number of cases of clonidine overdose admitted to a specialist paediatric hospital, with particular reference to the clinical features, clinical course and circumstances surrounding the incident.

METHODS

Cases of clonidine overdose were identified by review of the emergency department attendance register, the intensive care unit database and inpatient statistics collection. Case notes were reviewed to determine the clinical features, history and clinical course in each case.

RESULTS

Fifteen patients experienced 16 overdoses during the period 1990-97 inclusive. Only one case occurred before 1994. Depressed level of consciousness and bradycardia were the most common clinical manifestations, and were observed in 75 and 88% of cases respectively. There were no fatalities. Five patients received naloxone. Other treatment modalities included gastrointestinal decontamination, atropine, ventilation and inotropic support. Fourteen cases occurred in association with medication prescribed for attention-deficit hyperactivity disorder (ADHD).

CONCLUSION

Clonidine overdose is a potentially serious condition, often requiring intensive care management. Our experience suggests that it is a growing problem, related in part to its increased use in the treatment of ADHD. Preventive strategies, including raising the level of awareness of risks, changes to packaging and appropriate selection of patients for treatment, need consideration if further overdoses are to be prevented.

Clonidine poisoning in Jefferson County, Alabama

STUDY OBJECTIVE

To describe the epidemiology of clonidine-related hospitalization in children, to evaluate the efficacy of naloxone, and to review the clinical effects of clonidine toxicity.

METHODS

This was a retrospective analysis in an urban teaching pediatric emergency department with an annual census of 55,000 involving 80 children younger than 6 years who were admitted for clonidine ingestion during a 6-year period.

RESULTS

Clonidine commonly belonged to the patient's grand-mother (54%). Black children were twice as likely to be hospitalized for clonidine ingestion than white children compared with children hospitalized for any injury. Average time to onset of symptoms was 35 minutes. Decreased level of consciousness was the most common presenting symptom (96%). Mean ED vital signs were systolic blood pressure, 102 mm Hg; pulse, 98; respirations, 25 (six patients intubated); and temperature, 36.6 degrees C, Naloxone was administered to 49% of patients, 84% of whom demonstrated no response.

CONCLUSION

Clonidine ingestion is endemic in our area. Serious clinical effects mandate that all children with clonidine ingestion be triaged to a health care facility. Naloxone as an antidote for clonidine remains controversial.

Clonidine patch toxicity

Five published case reports of clonidine patch toxicity in pediatric patients bring to light the importance of educating the public regarding appropriate use and disposal of transdermal drug-delivery systems. With the increasing use of clonidine transdermal delivery systems it is important that clonidine patch toxicity be considered in pediatric patients presenting with symptoms of depressed consciousness, miosis, hypoventilation, hypotension, bradycardia, hypothermia, cardiac dysrhythmias, hypotonia, or convulsions. Appropriate early supportive management is essential to avoid serious morbidity or mortality in the pediatric patient, and is reviewed herein.