Gabapentin for clozapine-related seizures

Do Psychotropic Drugs Cause Epileptic Seizures? A Review of the Available Evidence

Psychiatric comorbidities in patients with epilepsy are common. A bidirectional relationship has been well described where not only patients with epilepsy have a higher prevalence of psychiatric comorbidities but also patients with primary psychiatric disorders are at an increased risk of developing seizures. The aim of this review is to highlight the complex relationship between epilepsy and common psychiatric disorders and to answer the question whether psychotropic medications are proconvulsant by reviewing the preclinical and clinical literature. The evidence shows that the majority of psychotropic medications are not proconvulsant when used in therapeutic doses with the exception of a subset of medications, mainly bupropion IR and certain antipsychotic drugs such as clozapine. An effective treatment of psychiatric comorbidities in patients with epilepsy must consider not only the potential therapeutic effect of the drug, but also its potential iatrogenic effects on the seizure disorder.

Clozapine-induced seizure

There are very few reports which suggest an association between antipsychotic clozapine low dose and seizure. We report a case in which intial titration of low dose clozapine developed seizure. A 42-year-old female who did not have any history of seizure and had normal blood parameters and normal computed tomography brain at the baseline developed seizure while on clozapine 300 mg/day. Reduction of the dose of clozapine to 250 mg/day led to the return to baseline, with having another episode of seizure on again increasing the dose of clozapine, requiring tablet haloperidol 10 mg/day as an add-on therapy for normalization of behavioral problems. Later, clozapine was maintained on 250 mg/day, with no recurrence of seizure episodes. To conclude, this case report suggests that clozapine can rarely lead to seizure during the initial phase of titration of treatment.

Low-dose Clozapine-induced Seizure: A Case Report

Seizures are believed to be a dose-dependent side effect of clozapine. In this case report, we describe a patient who had tonic-clonic seizures after using a low dose clozapine who did not have any seizure risk. The 29-year-old male patient had been followed-up with a diagnosis of schizophrenia for about 5 years. When using clozapine 200 mg/day he had a tonic-clonic seizure with bilateral diffuse epileptic activity in electroencephalography (EEG). In the literature, there are a few case reports about low-dose clozapine-induced seizure. Seizures were observed in our case with a low dose of clozapine (200 mg/day) making this case remarkable. EEG monitoring at regular intervals and examination of plasma levels of clozapine could be useful in preventing the development of seizures.

Seizure associated with clozapine: incidence, etiology, and management

Seizures are a known adverse effect of clozapine therapy. The literature varies on incidence rates of seizures, secondary to varying time frames in which each seizure occurred. Tonic-clonic seizures comprise the majority of seizures experienced secondary to clozapine use, but it is imperative to recognize the potential variety of seizure presentation. The exact etiology of clozapine-induced seizure is unknown. Conflicting reports regarding total oral dose, serum concentration, dose titration, and concomitant medications make it difficult to identify a single cause contributing to seizure risk. Following seizure occurrence, it may be in the best interests of the patient to continue clozapine treatment. In this clinical situation, the use of an antiepileptic drug (AED) for seizure prophylaxis may be required. The AED of choice appears to be valproate, but several successful case reports also support the use of lamotrigine, gabapentin and topiramate. Well-designed clinical trials regarding clozapine seizure prophylaxis are lacking. Given clozapine's strong evidence for efficacy in the treatment of schizophrenia and schizoaffective disorder, every attempt to manage side effects, including seizure, should be implemented to allow for therapeutic continuation.

Use of anticonvulsants as prophylaxis for seizures in patients on clozapine

OBJECTIVE

The aim of this study is to conduct a critical review of the literature regarding the use of anticonvulsants in the prophylaxis of clozapine-induced seizures, to examine the relationship of the latter with clozapine daily dose, serum concentration and other factors than dosage that effect clozapine blood concentration, and to make recommendations for the management of clozapine-induced seizures.

METHOD

A systematic review of English-language MEDLINE articles was undertaken.

CONCLUSIONS

Clozapine-induced seizures may occur at any dose; the risk increases with dose and goes up to 4% at ≥ 600 mg/day. Some authors have advocated that patients on that dose regimen have anticonvulsant added as a primary prophylactic measure. The author discusses the pitfalls of this recommendation and highlights that seizures are better predicted from serum concentration (1300 ng/ml) rather than dose alone, and that serum concentration is strongly influenced by sex, age, smoking habit, drug-drug interactions and variations in the 1A2, 2D6 and 3A4 genotypes. Anticonvulsants are not recommended as a primary prophylaxis for clozapine-induced seizures. When deemed necessary as secondary prophylaxis, the clinician's choice should consider drug-drug interactions that may increase/decrease clozapine serum concentration and lead to more side effects, including neutropenia/agranulocytosis and seizures, or compromise therapeutic response. Recommendations for primary and secondary prophylaxis of clozapine related-seizures are provided.

Cerebroventricular clozapine would be a viable treatment modality for clozapine-dependent schizophrenia patients with neutropenia

The atypical antipsychotic clozapine is very effective for treatment of schizophrenia, but it causes agranulocytosis requiring drug cessation in up to 2% of cases. There has been some success rechallenging with clozapine at a later date or giving granulocyte colony stimulating factor or lithium while continuing clozapine. However, there are still some patients for whom these strategies do not work yet who cannot be controlled on other medications. This paper proposes that for such individuals, cerebroventricular administration of clozapine via Ommaya catheters could allow continued use of clozapine therapy. Direct infusion into cerebrospinal fluid means far smaller amounts of drug would be needed for efficacy, and clozapine concentrates in the central nervous system where it would not be exposed to bone marrow stem cells to cause agranulocytosis. This treatment paradigm would also provide a means for court-ordered clozapine therapy and a possible delivery system for future therapeutics based on trophic factors such as brain-derived neurotrophic factor.

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).

Use of lamotrigine in a patient with a clozapine-related seizure

Seizures can be a serious adverse effect of clozapine, often a last-resort antipsychotic with unique efficacy for some patients. Several anticonvulsants have been reported to be useful in preventing further clozapine-induced seizures and permitting continued treatment with this medication. The authors describe the first reported successful use of lamotrigine for this purpose.

Clozapine: Current perspective

The author conducted a review of studies that compared the efficacy, tolerability and indication for the use of clozapine in current perspectives for the treatment of resistant schizophrenia/ partial responders.

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.

Somatic augmentation strategies in clozapine resistance--what facts?

BACKGROUND

Polypharmacy without evidence-based support is sometimes needed for patients treated with 40% to 70% clozapine who are clozapine nonresponders. Several somatic augmentation strategies are proposed in the scientific literature, with different levels of evidence for safety and efficacy.

OBJECTIVES

The purpose of the present study is to review the available literature on the efficacy and safety of clozapine augmentation with somatic agents other than antipsychotics. The following classes of agents are considered: (1) mood stabilizers, (2) antidepressants, (3) electroconvulsive therapy and repetitive transcranial magnetic stimulation, (4) glutamatergic agents, (5)fatty acids supplements, and (6) benzodiazepines.

RESULTS

Case controls and small-size clinical trials largely dominate the literature, limiting the power to draw conclusions concerning safety issues and the meaning of negative studies. Moreover, variable definitions of clozapine resistance, heterogeneous outcome measures, and short duration of treatment trials are additional limitations.

CONCLUSION

Generally, adjunctive strategies for clozapine-resistant patients remain based on scarce evidence of efficacy and significant safety concerns. Low-frequency repetitive transcranial magnetic stimulation, fatty acids supplements, and mirtazapine showed good tolerability and some efficacy, but the results need replication.

Interactions between Antiepileptic and Antipsychotic Drugs

Antiepileptic and antipsychotic drugs are often prescribed together. Interactions between the drugs may affect both efficacy and toxicity. This is a review of human clinical data on the interactions between the antiepileptic drugs carbamazepine, valproic acid (sodium valproate), vigabatrin, lamotrigine, gabapentin, topiramate, tiagabine, oxcarbazepine, levetiracetam, pregabalin, felbamate, zonisamide, phenobarbital and phenytoin with the antipsychotic drugs risperidone, olanzapine, quetiapine, clozapine, amisulpride, sulpiride, ziprasidone, aripiprazole, haloperidol and chlorpromazine; the limited information on interactions between antiepileptic drugs and zuclopenthixol, periciazine, fluphenazine, flupenthixol and pimozide is also presented. Many of the interactions depend on the induction or inhibition of the cytochrome P450 isoenzymes, but other important mechanisms involve the uridine diphosphate glucuronosyltransferase isoenzymes and protein binding. There is some evidence for the following effects. Carbamazepine decreases the plasma concentrations of both risperidone and its active metabolite. It also decreases concentrations of olanzapine, clozapine, ziprasidone, haloperidol, zuclopenthixol, flupenthixol and probably chlorpromazine and fluphenazine. Quetiapine increases the ratio of carbamazepine epoxide to carbamazepine and this may lead to toxicity. The data on valproic acid are conflicting; it may either increase or decrease clozapine concentrations, and it appears to decrease aripiprazole concentrations. Chlorpromazine possibly increases valproic acid concentrations. Lamotrigine possibly increases clozapine concentrations. Phenobarbital decreases clozapine, haloperidol and chlorpromazine concentrations. Phenytoin decreases quetiapine, clozapine, haloperidol and possibly chlorpromazine concentrations. There are major gaps in the data. In many cases there are no published clinical data on interactions that would be predicted on theoretical grounds.