Myoclonic epileptic seizures during clozapine treatment: a report of three cases

Electric Shock Sensation and Recurrent Falls as a Side Effect of Clozapine Therapy: A Case Report

Clozapine is an atypical antipsychotic that acts by blocking mainly dopamine 4 receptors. It is usually prescribed for treatment-resistant schizophrenia as well as treatment-resistant bipolar disorder. Clozapine has a wide profile of side effects that result from blocking different receptors all over the body. A 42-year-old Middle Eastern female is known to have suffered from schizoaffective disorder for many years and had frequent relapses despite compliance with treatment. She was commenced on Clozapine; the patient started complaining of an electric shock sensation throughout her body that resulted in recurrent falls with bilateral leg fractures. She was started on sodium valproate to exclude the possibility of seizure activity but the electric shock sensation did not subside. The decision was made to switch her to aripiprazole and gradually taper down and stop Clozapine which improved her symptoms. Careful monitoring of patients who receive Clozapine is recommended especially during the tapering phase due to the risky adverse events it can bring about. It is essential to understand the side effects in order to tackle them as soon as they arise.

Clozapine-induced myoclonus: a case report and review of the literature

We describe the case of a young man with treatment-resistant schizophrenia, who developed myoclonus during clozapine titration. This subsequently led to a full tonic-clonic seizure. Clozapine treatment can result in a range of seizure-like activity, the most well-known being tonic-clonic seizures. This case highlights the importance of recognizing and treating clozapine-induced myoclonus, as it can herald the onset of a full seizure, even at low serum clozapine levels. We highlight the variety of ways myoclonus can present clinically and suggest treatment options.

Clozapine-related EEG changes and seizures: dose and plasma-level relationships

Clozapine is a widely used atypical antipsychotic with a unique effectiveness in treatment-resistant schizophrenia. An important adverse effect is seizures, which have been observed at all stages of clozapine treatment. Valproate has traditionally been considered the drug of choice for the prophylaxis of clozapine seizures, however it may not be the most suitable choice for all patients. There is disagreement as to the best point to prescribe valproate or a suitable antiepileptic: as seizure prophylaxis at a certain clozapine dose or level, or only as remedial treatment. In this review, we examine the relevant literature with an aim to evaluate the following relationships: clozapine dose and electroencephalogram (EEG) abnormalities, plasma levels and EEG abnormalities, dose and occurrence of seizures and plasma levels and occurrence of seizures. Weighted linear regression models were fitted to investigate these relationships. There was a strong relationship between clozapine dose and plasma level and occurrence of clozapine-induced EEG abnormalities. However, a statistically significant relationship between dose and occurrence of seizures was not found. A relationship between clozapine plasma level and occurrence of seizures was not established because of the scarcity of useful data although our review found three case reports which suggested that there is a very substantial risk of seizures with clozapine plasma levels exceeding 1300 μg/l. Seizures are more common during the initiation phase of clozapine treatment, suggesting a slow titration to target plasma levels is desirable. An antiepileptic drug should be considered when the clozapine plasma level exceeds 500 μg/l, if the EEG shows clear epileptiform discharges, if seizures, myoclonic jerks or speech difficulties occur and when there is concurrent use of epileptogenic medication. The antiepileptics of choice for the treatment and prophylaxis of clozapine-induced seizures are valproate (particularly where there is mood disturbance) and lamotrigine (where there is resistance to clozapine).

Clozapine-induced seizures: recognition and treatment

OBJECTIVES

To inform clinicians about the types of seizures that can be induced by clozapine and to provide recommendations for treatment.

METHODS

We identified articles on clozapine-induced seizures from a MEDLINE search of the English-language literature from 1978 to July 2006. The frequency of each type of seizure and the dosages of clozapine associated with seizures were compiled. In addition to this review, we report a new case illustrating the challenge of diagnosing subtle seizure activity.

RESULTS

The tonic-clonic variety is the most frequently described clozapine-induced seizure. Myoclonic and atonic seizures together constitute about one-quarter of the reported seizures. The mean dosage of clozapine associated with seizures is not high (less than 600 mg daily).

CONCLUSIONS

It may be difficult for clinicians to recognize subtle types of clozapine-induced seizures, such as myoclonic, atonic, or partial seizures. Clinicians should not place excessive reliance on the plasma level of clozapine or electroencephalogram findings to predict the occurrence of seizures. When a first seizure occurs, it is recommended that the dosage of clozapine be reduced or an alternative antipsychotic agent be employed. If a second seizure occurs, an anticonvulsant drug should be started. Special attention should be paid when commencing or discontinuing concurrent medication that may affect the plasma level of clozapine.

A review of clozapine safety

Clozapine is a distinctive antipsychotic agent, having a unique clinical profile and an idiosyncratic safety profile. More so than with other agents, the weighting of its adverse event profile is critical, in order to counterbalance its clear clinical advantages. The safety issues with clozapine are in a number of areas, some of which are considered medical emergencies and potentially life-threatening. These include haematological (neutropenia and agranulocytosis), CNS (seizures), cardiovascular (myocarditis and cardiomyopathy), metabolic (diabetes), gastrointestinal and neuromuscular. Understanding the safety profile of clozapine allows an informed use of the agent that can maximise its clear clinical benefit and minimise the known risks.

Clozapine therapy in patients with neurologic illness

OBJECTIVE

This review will analyze the use of clozapine in patients with neurologic illness.

METHODS

A review of the literature was performed. Attention is focused particularly on patients with seizure disorder, head injury, mental retardation, Parkinson's disease, Huntington's disease, tardive dyskinesia, and selected other neurological disorders.

RESULTS

This review discusses clinical difficulties/issues associated with clozapine therapy in patients with a variety of neurological disorders.

CONCLUSION

Although clozapine therapy should be reserved for those patients who are refractory to conventional psychotropic medications, when used appropriately it may offer a safe and effective way of improving quality of life for patients with behavioral symptoms and neurologic illness.

Spectrum of EEG abnormalities during clozapine treatment

Clozapine is a novel antipsychotic agent effective in treating refractory schizophrenia. Clozapine produces fewer extrapyramidal effects than other neuroleptics, although agranulocytosis and seizures are significant adverse effects. To characterize the spectrum of clozapine-related electroencephalographic abnormalities, we identified 10 patients who had electroencephalograms (EEGs) performed before and during clozapine treatment. These 10 patients represented a subset of individuals participating in an investigational trial. During clozapine treatment, five developed myoclonus and one experienced a generalized tonic-clonic seizure. Records were retrospectively reviewed by an electroencephalographer blinded to the patient's history and medications. All patients had normal EEGs before clozapine treatment. While receiving clozapine (250-900 mg daily), all patients developed background slowing in the theta and often delta ranges. Additionally, 7 patients exhibited bilateral spike, polyspike and slow wave discharges, one with a photoparoxysmal response. Follow-up EEGs performed in 4 of these 7 patients after a decrease in clozapine dosage and/or addition in valproic acid showed diminished epileptiform activity.