Pediatric clozapine intoxication

Development and validation of a risk prediction nomogram for disposition of acute clozapine intoxicated patients to intensive care unit

BACKGROUND

Clozapine is an atypical antipsychotic drug used for the treatment of refractory schizophrenia. It is reported as the most toxic in its class. Using serum clozapine level as a severity indicator is doubtful and unfeasible, particularly in low resourced countries.

METHODS

This is an extended two-phase retrospective study that utilized medical records of patients diagnosed with acute clozapine intoxication and admitted to Tanta University Poison Control Center, Egypt during the past 6 years. Two hundred and eight medical records were used to establish and validate a nomogram for predicting the need for intensive care unit (ICU) admission in acute clozapine intoxicated patients.

RESULTS

A reliable simple bedside nomogram was developed and proved its significant ability to predict the need for ICU admission, with an area under the curve (AUC) of 83.9% and 80.8% accuracy. It encompassed the age of admitted patients (AUC = 64.8%, p = .003), respiratory rate (AUC = 74.7%, p < .001), O₂ saturation (AUC = 71.7%, p < .001), and random blood glucose level upon admission (AUC = 70.5%, p < .001). External validation of the proposed nomogram showed a high AUC (99.2%) with an overall accuracy of 96.2%.

CONCLUSION

There is a need to develop a reliable objective tool predicting the severity and need for ICU admission in acute clozapine intoxication. The proposed nomogram is a substantially valuable tool to estimate ICU admission probabilities among patients with acute clozapine intoxication and will help clinical toxicologists make rapid decisions for ICU admission, especially in countries with low resources.

Clozapine Toxicity in Two Young Siblings Due to a Pharmacy Dispensing Error: a Pediatric Case Report

INTRODUCTION

Clozapine is an atypical antipsychotic used to treat refractory schizophrenia; in both therapeutic use and overdose, it can cause significant toxicity. We report two young siblings who developed altered mental status after ingesting clozapine due to a pharmacy dispensing error.

CASE REPORT

A 5-year-old girl and her 19-month-old sister presented to the emergency department (ED) with altered mental status after they took their first dose of what was believed to be cimetidine, prescribed to treat molluscum contagiosum. Both children were discharged after a brief period of observation in the ED. Two days later, when the older child continued to be symptomatic, their mother used a web-based pill identifier and discovered that the pills dispensed by the pharmacy were 200 mg clozapine tablets, not the cimetidine that had been prescribed. Ingestion was confirmed with an elevated serum clozapine concentration in the older child of 17 mcg/L at 85 hours post-ingestion (adult therapeutic range: 350-600 mcg/L). Both children had complete resolution of their symptoms 4 days following the ingestion with supportive care alone.

DISCUSSION

We report two cases of pediatric clozapine toxicity due to a pharmacy dispensing error. The error was due, in part, to similarly named medications being stored adjacent to each other on a shelf. Dispensing errors are not rare occurrences and their root causes are multi-factorial. This case demonstrates the importance of reducing such errors, particularly for medications with potential for severe toxicity.

Clozapine Intoxication Mimicking Acute Stroke

Clozapine is an atypical antipsychotic drug prescribed for treatment-resistant schizophrenia. The risk of adverse hematologic, cardiovascular, and neurologic effects has tempered its use, and reports of overdoses remain rare. We report a case of accidental acute clozapine intoxication in a clozapine-naïve patient, who presented with symptoms mimicking acute stroke and later developed status epilepticus. Clozapine intoxication is a rare presentation in the emergency department with potential for iatrogenic harm if not correctly identified.

Accidental clozapine intoxication in a toddler: clinical and pharmacokinetic lessons learnt

WHAT IS KNOWN AND OBJECTIVE

Clozapine, a second generation antipsychotic which is relatively safe in overdose, has been used as an effective treatment alternative to traditional antipsychotics. The therapeutic use in children remains controversial. However, in accordance with the increasing prescription in adults, the accidental ingestion in childhood becomes more frequent. We report the youngest case of accidental clozapine ingestion.

CASE SUMMARY

A 13-month-old girl presented with acute respiratory insufficiency and coma of unknown origin. The medical history, laboratory and radiological assessment did not link to aetiology until an almost spontaneous arousal after 22 h pointed towards intoxication. The initial standard drug screening using immunoassay had been negative. Hence, liquid chromatography mass spectrometry/mass spectrometry (LC-MS/MS) was performed, and clozapine was detected with a serum concentration of 736 ng/mL.

WHAT IS NEW AND CONCLUSION

This case illustrates the diagnostic and forensic pitfalls in a coma of unknown origin due to the limits of toxicological screening immunoassays. LC-MS/MS analysis by an established method showed clozapine metabolites (norclozapine and clozapine-N-oxide) are detectable for longer period, especially in urine, when compared with clozapine. The clinical course is presented in unique correlation with plasma and urine concentrations of clozapine and its metabolites. The elimination pattern of clozapine in toddlers is similar to adults, and the toxic dose was found to be lower when compared with school-age children and adults.

Development of a method of clozapine dosage by selective electrode to the iodides

Clozapine (Leponex(®)), the main neuroleptic indicated in the treatment of resistant schizophrenia, requires therapeutic monitoring because of its side effects and the individual variability in metabolism. In addition, several cases of intoxication by this drug were described in the literature. In this work, we studied the indirect dosage of clozapine by selective electrode to the iodides for the optimization of an analytical protocol allowing therapeutic monitoring and the diagnosis of intoxication and/or overdose. Our results showed that the developed method is linear between 0.05 and 12.5 µg/mL (r = 0.980), with a limit of detection of 0.645.10(-3) µg/mL. It presents good precision (coefficient of variation less than 4%) and accuracy (coefficient less than 10%) for all the studied concentrations. With a domain of linearity covering a wide margin of concentrations, this method can be applicable to the dosage of clozapine in tablets and in different biological matrices, such as plasma, urines, and postmortem samples.

Antipsychotic poisoning in young children: a systematic review

The aim of this review was to determine the spectrum and severity of effects of unintentional antipsychotic poisoning in children. A computerised literature search of MEDLINE (1966 to February 2005) and EMBASE (1980 to February 2005) was undertaken. The Internet was searched using URL: www.google.com. The proceedings of the North American Congress of Clinical Toxicology (NACCT) and the European Association of Poisons Centres and Clinical Toxicologists (EAPCCT) were hand searched. All cases of unintentional antipsychotic (all classes) poisoning in children aged 0-6 years were included. The data extracted included the age, weight, antipsychotic, dose, clinical effects, treatment and outcomes. The toxic dose was estimated as the lowest dose causing objective adverse effects.Sixty-eight reports were identified. Few contained all of the required information. Most of the case series included multiple antipsychotics with limited information on individual drugs or all ages with limited paediatric information. For most antipsychotics the ingestion of one tablet caused symptoms that were sometimes severe and usually lasted from 1 to 3 days. Extrapyramidal symptoms (EPS) were often delayed for up to 12-24 hours. Chlorpromazine caused CNS depression, hypotension and miosis; EPS and cardiac effects were rare, and the toxic dose was estimated to be 15 mg/kg. Haloperidol caused drowsiness (rarely coma) and over one-half of patients had neuromuscular effects (mainly EPS), with a toxic dose estimated at 0.15 mg/kg. Thioridazine caused CNS depression and potentially cardiac effects, with a toxic dose of 1.4 mg/kg. Atypical antipsychotics caused significant CNS depression (except risperidone); EPS were less common. Toxic doses were clozapine 2.5 mg/kg, olanzapine 0.5 mg/kg and aripiprazole 3 mg/kg. EPS responded to anticholinergic drug treatment. In summary, unintentional antipsychotic ingestion in children can cause severe effects that last 1-3 days, often with one tablet. Children potentially ingesting a toxic dose or who are symptomatic should be considered for assessment in hospital. Most cases resolve with good supportive care. Toxic doses are only estimates that are based on limited data and should be used with caution until prospective studies are undertaken.

Suspected clozapine poisoning in the UK/Eire, 1992–2003

OBJECTIVE

Toxicological analyses are often performed to investigate suspected poisoning, but the interpretation of results may not be straightforward. We studied suspected poisoning cases 1992-2003 where blood clozapine and N-desmethylclozapine (norclozapine) were measured in order to assess the relationship of these parameters to outcome.

METHODS

Samples were referred from clinicians, pathologists/coroners, or via the Clozaril Patient Monitoring Service (CPMS, Novartis). Information was gathered from clinical, post-mortem, or coroners' reports.

RESULTS

There were seven fatal [five male, two female; median (range) age 28 (24-41) year] and five non-fatal [four male, one female; median age 35 (26-41) year] clozapine overdoses. The median post-mortem blood clozapine and norclozapine concentrations were 8.2 (3.7-12) and 1.9 (1.4-2.4)mg/L, respectively [median clozapine:norclozapine ratio 4.4 (2.9-5.1)]. The median plasma clozapine and norclozapine concentrations (first or only sample) were 3.9 (1.7-7.0) and 0.40 (0.30-0.70)mg/L, respectively [median clozapine:norclozapine ratio 7.6 (5.3-18)] in the remainder. These overdoses were in patients who were poorly or non-adherent to clozapine, or who had taken tablets prescribed for someone else. In 54 further people who died whilst receiving clozapine [38 male, 16 female; median age 41 (22-70) year], the median post-mortem blood clozapine and norclozapine concentrations were 1.9 (0-7.7, n = 43) and 1.4 (0-6.0, n = 39)mg/L, respectively [median clozapine:norclozapine ratio 1.5 (0.4-7.6, n = 38)]. The median post-mortem increase in blood clozapine and norclozapine as compared to the most recent ante-mortem measurement was 489 (98-5,350)% and 371 (139-831)%, respectively [median sample time before death 14 (0-30, n = 21) days].

CONCLUSION

Clozapine poisoning cannot be diagnosed on the basis of blood clozapine and norclozapine concentrations alone. The analysis of ante-mortem blood specimens collected originally for white cell count monitoring and the blood clozapine:norclozapine ratio may provide additional interpretative information.

Overdoses and ingestions of second-generation antipsychotics in children and adolescents

OBJECTIVE

We reviewed the available published data on intentional or unintentional secondgeneration antipsychotic overdoses in children and adolescents. The prescribing of secondgeneration antipsychotics has continued to increase over the past decade for children, adolescents, and adults. The authors reviewed the existing literature to determine the circumstances, presenting problems, treatment, and outcomes of youths who were exposed to nontherapeutic doses of these medications.

METHODS

A systematic English-language Medline search of all reports (1989-2005) and a review of the bibliographies of all articles obtained was done to identify papers reporting an overdose or ingestion of a second-generation antipsychotic. Data were reviewed on clozapine, risperidone, olanzapine, ziprasidone, quetiapine, and aripiprazole. The annual reports of the American Association of Poison Control Centers National Data Collection System were reviewed from 1990 to 2003, the most recent report currently available. All fatalities in children and youths under 18 years of age were included.

RESULTS

The literature review identified 40 reports that included 63 patients, ranging in age from 1 day to 17 years of age. The clinical presentations included drowsiness, lethargy, agitation, irritability, combativeness, and tachycardia. There were 11 fatalities in the cases reviewed, 1 from clozapine overdose, 3 from risperidone overdose, 2 from olanzapine overdose, and 5 from quetiapine overdose. All other cases reported no significant sequelae and resolved without any reported clinical consequences. Duration of overdose symptoms ranged from 24 hours to 7 days. One case of clozapine intoxication showed resolution of symptoms in 6 hours and, in another case of olanzapine overdose, symptoms resolved in 13 days. The most frequently employed treatments included intubation, gastric lavage, activated charcoal, intravenous fluids, artificial respiration, and restraints or sedatives.

CONCLUSIONS

There is a need for future case reports to include serum medication level, weight of patient, coingestants, the health of the patient at baseline, relevant laboratory and toxicology studies and a standardized scale to rate the level of consciousness, such as the Glasgow Coma Scale. The existing pharmacovigilance data reports indicate these medications are relatively safe when taken in overdose, particularly when coingestants are not involved.

Are 1 or 2 dangerous? Clozapine and olanzapine exposure in toddlers

Clozapine (Clozaril) and olanzapine (Zyprexa) are two relatively new atypical antipsychotics that are structurally and pharmacologically related. There are currently no therapeutic indications for these pharmaceuticals in infants and toddlers.Presumably, as the usage of these medications in adults increases, the frequency of unintentional pediatric ingestions will increase. In 2001 the annual report of the American Association of Poison Control Centers Toxic Exposure Surveillance System included a separate subcategory for atypical antipsychotics under the heading of sedatives/hypnotics/antipsychotics. The toxidrome resulting from these drugs is predominately central nervous system depression and anticholinergic effects. Although the desirable lack of extrapyramidal symptoms in adults results in their greatest clinical utility, several reports of toxic ingestions in small children are noteworthy for having extrapyramidal manifestations. We review here the available reported clinical experience with toxic doses of these medications that in small children may amount to as little as a single tablet. Although such doses may be lethal, supportive care and gastrointestinal decontamination in this population will generally lead to a good outcome.

Munchausen syndrome by proxy (MSBP): an extreme form of child abuse with a special forensic challenge

Munchausen syndrome by proxy (MSBP) is a special form of child abuse in which an adult repeatedly produces symptoms of illness in a person under his/her care. In most cases the perpetrators are mothers who repeatedly and in different ways produce or feign symptoms of illness in their children in order to obtain medical treatment for them. MSBP is thus a special form of child abuse that is also of importance in the field of forensic medicine and a particular challenge to the medicolegal expert. We report two cases of poisoning with different substances (clozapine and clonidine) detected by toxicological investigations at our Department of Legal Medicine. The relevance of the problem for the medicolegal expert and the importance of an interdisciplinary co-operation are pointed out.

Effect of post-mortem changes on peripheral and central whole blood and tissue clozapine and norclozapine concentrations in the domestic pig (Sus scrofa)

Interpretation of the results of psychoactive or other drug measurements in post-mortem blood specimens may not be straightforward, in part because analyte concentrations in blood may change after death. There is also the issue of comparability of plasma (or serum) results to those obtained in whole blood. To investigate these problems with respect to clozapine, this drug (10mg/kg daily) was given orally to two pigs. Blood was collected 3h post-dose on day 7, the animals were sacrificed, and blood taken from central and peripheral veins for up to 48 h after death. Tissue samples were also collected immediately after death and at 48 h. Ante-mortem whole blood clozapine/N-desmethylclozapine (norclozapine) concentrations were 0.86/1.07 and 1.11/1.15 mg/l in pigs 1 and 2, respectively. Blood clozapine and norclozapine concentrations generally increased after death (central vein: clozapine up to 300%, norclozapine up to 460%; peripheral vein: clozapine up to 155%, norclozapine up to 185%). Initial blood and kidney clozapine and norclozapine concentrations were comparable in both animals, but were some two-fold higher in heart, liver and striated muscle in pig 2. In both animals, the heart and striated muscle clozapine and norclozapine concentrations had increased some two- to three-fold at 48 h, whilst the liver and kidney concentrations were essentially unchanged. The reason for the increase in heart and striated muscle concentrations at 48 h is unclear, but could be simple variation in sample site. The plasma:whole blood distribution of clozapine and norclozapine was studied in vitro. In human blood (one volunteer donor, haematocrit 0.50) the plots of plasma versus whole blood concentration were linear for both analytes across the range 0.1-1.5mg/l, although clozapine favoured plasma (plasma:whole blood ratio=1.12), whereas norclozapine favoured whole blood (ratio 0.68). In pig blood, the plots of plasma versus whole blood were non-linear in both cases, although clozapine favoured plasma to a greater extent than norclozapine. This may be due to lower plasma clozapine and norclozapine protein binding capacity in the pig as compared to man.

Clozapine intoxication in a dog

Intoxication with clozapine in a dog, suspected from history and clinical signs at presentation, was confirmed by demonstration of decreasing serum levels of this drug. Clozapine is a tricyclic dibenzodiazepine used for treatment of human schizophrenia, and clinical signs of intoxication in humans include tachycardia, seizures, muscle fasciculations, agitation, and sialorrhea. This dog showed ptyalism, hyperthermia, tachycardia, and was easily excited by tactile or auditory stimulation. The calculated peak concentration of clozapine in this dog was approximately 6,000 ng/mL, and the elimination half-life (t(1/2)) was 5 hours. Charcoal administration and supportive care led to a successful outcome in this patient.

The pharmacology and toxicology of atypical antipsychotic agents

Recently, atypical antipsychotic agents have largely replaced traditional agents as first-line drugs for the treatment of schizophrenia. It is likely that atypical agents will soon account for the majority of poisonings from antipsychotic agents that present to health care facilities in the US. This article reviews the pharmacodynamics, pharmacokinetics, and toxicology of atypical antipsychotic drugs, chiefly clozapine, risperidone, olanzapine, and quetiapine. A descriptive summary of the human overdose experience with these agents is provided. Adverse effect and drug interaction data are reviewed. Based on the available pharmacodynamic, pharmacokinetic, and human overdose data, recommendations on management are provided.

Loss of consciousness from acute quetiapine overdosage

BACKGROUND

Quetiapine (Seroquel) is a new atypical antipsychotic agent developed for the treatment of schizophrenia. This dibenzothiazepine derivative possesses high affinity for 5-HT2 receptors with lower affinity for D1 and D2 dopamine receptors. In comparison to other antipsychotic agents, quetiapine has less antimuscarinic and alpha1 antagonist receptor activity. Overdose reports outside of clinical trials are limited. We report an intentional overdose of quetiapine by a schizophrenic.

CASE REPORT

A 26-year-old female presented to the emergency department following an alleged ingestion of greater than 10,000 mg of quetiapine. At 1 1/2 hours postingestion, the patient was awake, ambulatory, and responded to verbal stimuli. At 2 1/2 hours postingestion, the patient experienced a decreased level of consciousness and responded only to deep pain. Physical findings included sinus tachycardia, pupils 3-4 mm and sluggish, and BP 135/70. Within 16 hours, the patient became awake and alert and was subsequently extubated. Serum electrolytes and blood count were unremarkable. The electrocardiogram at 18 hours postingestion showed a sinus tachycardia, which lasted for approximately 40 hours postingestion. A follow-up electrocardiogram at 42 hours postingestion was normal.

CONCLUSION

This ingestion resulted in the loss of consciousness with need for airway protection and persistent tachycardia. Major overdoses of quetiapine warrant close observation in an intensive care setting.

The use of psychotropic medication in preschoolers: indications, safety, and efficacy

OBJECTIVE

To review the indications, safety and efficacy of psychotropic medications used in preschoolers.

METHODS

Proprietary prescription-use databases indicate that practitioners are prescribing psychotropic medications for preschool patients at an increasing rate. A Medline search was conducted using drug exposure for children below the age of 6 years to identify efficacy and safety reports of these agents in the preschool age-group.

RESULTS

The search yielded 22 reports that mention exposure to medications, including maternal exposure, accidental overdose, and adverse events in preschool children. Safety issues highlight the age-specific vulnerabilities of this age-group, including hepatotoxicity from valproic acid, among others. In addition, the prominence of adverse-event responses in this age group may be related to polypharmacy not seen in school-age children or adolescents. Less than a dozen controlled efficacy studies of psychotropic agents were identified for children in the preschool age-group. These are limited by the small numbers of subjects in the reports. Only 2 disorders described in the Diagnostic and Statistical Manual of Mental Disorder (DSM-IV), attention-deficit hyperactivity disorder (ADHD) and autistic disorder, are mentioned. The Food and Drug Administration (FDA) approved psychotropic medications for preschoolers but limited their use to medical purposes, not psychiatric, with the exception of use for ADHD.

CONCLUSION

Because data about psychotropic drug safety and efficacy in adults have not been extended to children, new psychopharmacological research is required before clinicians can use these agents to treat psychiatric disorders in the preschool age-group.