Three-year experience with ziprasidone exposures

Overdose of atypical antipsychotics: clinical presentation, mechanisms of toxicity and management

Historically, treatment for schizophrenia focused on sedation. The advent of the typical antipsychotics resulted in treatment aimed specifically at the underlying disease, but these agents were associated with numerous adverse effects, and were not particularly effective at treatment of the negative symptoms of schizophrenia. As a result, numerous atypical agents have been developed over the past 2 decades, including several agents within the past 5 years. Overdose of antipsychotics remains quite common in Western society. In 2010, poison control centres in the US received nearly 43,000 calls related to atypical antipsychotics alone. Due to underreporting, the true incidence of overdose with atypical antipsychotics is likely much greater. Following overdose of an atypical antipsychotic, the clinical effects observed, such as CNS depression, tachycardia and orthostasis are largely predictable based on the unique receptor binding profile of the agent. This article, which focuses on the atypical antipsychotics commonly used in the treatment of schizophrenia, discusses the features commonly encountered in overdose. Specifically, agents that result in QT prolongation and the corresponding potential for torsades de pointes, as well as unique features encountered with the various medications are discussed. The diagnosis of this overdose is largely based on history. Routine use of drug screens is unlikely to be beneficial. The primary goal of management is aggressive supportive care. Patients with significant CNS depression with associated loss of airway reflexes and respiratory failure need advanced airway management. Hypotension should be treated first with intravenous fluids, with the use of direct acting vasopressors reserved for persistent hypotension. Benzodiazepines should be used for seizures, with barbiturates used for refractory seizures. Intravenous magnesium can be administered for patients with a corrected QT interval exceeding 500 milliseconds.

Digital Holter measurement of QT prolongation in ziprasidone overdose

OBJECTIVE

QT prolongation is an important complication in drug overdose, particularly with some antidepressants and antipsychotics. There are problems with the accurate measurement of the QT interval and determining for what QT interval patients should be monitored, because of the risk of torsades des pointes (TdP). We report a case of ziprasidone overdose with QT prolongation, demonstrating different methods of measuring the QT interval.

CASE REPORT

A 47-year-old female presented after taking 1.2 g of ziprasidone and 250 mg of diazepam. She was taking propranolol and venlafaxine therapeutically. She developed bradycardia and QT prolongation (540 msec). She was transferred to a telemetry bed and observed for 48 h until her QT interval returned to normal (460 msec). QT intervals were extracted from (1) 12-lead digital Holter recordings (gold standard); (2) automated measurements on standard electrocardiograms (ECGs); and (3) manual measurements on standard ECGs, and compared on a QT versus time plot. An abnormal QT was determined based on the QT nomogram. Manual QT measurements showed a clear temporal association between ziprasidone overdose and a long QT, consistent with accurate QT measurements using continuous 12-lead Holter recordings with automatic QT measurements. However, standard automated measurements did not indicate an abnormal QT.

CONCLUSIONS

Manual measurement of the QT interval appeared to be similar to the more accurate measurement of the QT by automated digital Holter recordings and better than standard automated measurements. Manual QT measurements would be more appropriate in clinical assessment of patients.

Respiratory failure following isolated ziprasidone ingestion in a toddler

Ziprasidone is an atypical antipsychotic approved for the treatment of schizophrenia and bipolar mania in adults and is used off label in children and adolescents. Despite increasing use of ziprasidone in both adult and pediatric populations, there remains a paucity of reports describing unintentional pediatric exposures. The following report describes a patient with isolated ziprasidone ingestion who required intubation secondary to respiratory failure. A 15-month-old previously healthy boy presented to the emergency department shortly after his father found him with approximately five partially dissolved 80-mg ziprasidone tablets in his mouth. The child was flaccid and lethargic with no eye opening, withdrawing from pain only. Two hours after arrival, he developed worsening CNS depression with inability to protect his airway and underwent endotracheal intubation. A serum ziprasidone level was 330 ng/mL by LC/MS. The patient was extubated approximately 14 h later and was discharged from the hospital shortly thereafter in good health without neurological sequelae. Isolated pediatric ingestion of ziprasidone resulting in the need for significant medical intervention has not been previously reported. We report a case of respiratory failure requiring intubation following accidental ziprasidone ingestion with confirmatory serum levels.

A systematic review of cardiovascular effects after atypical antipsychotic medication overdose

As the use of atypical antipsychotic medications (AAPMs) increases, the number of overdoses continues to grow. Cardiovascular toxicity was common with older psychiatric medications but seems uncommon with AAPM. We conducted a systematic literature review to describe the cardiovascular effects reported after overdose of 5 common AAPM: aripiprazole, olanzapine, quetiapine, risperidone, and ziprasidone. We included case reports and case series describing overdose of these 5 medications identified in a search of MEDLINE, EMBASE, and abstracts from major toxicology meetings. We found 13 pediatric cases (age, <7 years), 22 adolescent cases (age, 7-16 years), and 185 adult cases. No pediatric case described a ventricular dysrhythmia or a cardiovascular death. In the adolescent and adult cases, we found numerous reports of prolonged corrected QT interval and hypotension, but there were only 3 cases of ventricular dysrhythmia and 3 deaths that may have been due to direct cardiovascular toxicity. The results from case series reports were similar to the single case report data. Our review suggests that overdose of AAPM is unlikely to cause significant cardiovascular toxicity.

Pattern of ziprasidone exposures reported to Texas poison centers, 2001-2005

Information on potentially adverse exposures to the atypical antipsychotic drug ziprasidone is limited. This study described the pattern of exposures involving only ziprasidone (isolated exposures) reported to Texas poison control centers during 2001-2005. The mean dose was 666 mg. The patient age distribution was <or=5 years (11%), 6-19 years (30%), and >or=20 years (60%). The exposures were intentional in 53% of the cases. Seventy-five percent of the exposures were managed at health care facilities. The final medical outcome was classified as no effect for 39% of the cases and minor effects for 40% of the cases. Adverse clinical effects were listed for 53% of the patients; the most frequently reported being neurological (42%), cardiovascular (13%), and gastrointestinal (5%). The most frequently listed treatment was decontamination by charcoal (34%) or cathartic (28%). Potentially adverse ziprasidone exposures reported to poison control centers are likely to involve management at a health care facility and involve some sort of adverse clinical effect. With proper treatment, the outcomes of such exposures are generally favorable.