An Irish case of pulmonary emboli secondary to clozapine therapy

Clozapine-Related Thromboembolic Events

Clozapine is an atypical antipsychotic used for treatment-resistant schizophrenia. Venous thromboembolism (VTE) is a rare side effect of clozapine which can be fatal. This article summarizes current evidence regarding the risk of VTE associated with the use of clozapine. We performed a PubMed (MeSH) and Google Scholar search for the last two decades. Studies or case reports performed in humans were included in the review, of which 42 case reports of patients taking clozapine at VTE onset were included in the analysis of this review. According to the articles reviewed, the mean age was 42.9 years, with more males (71.43%) than females (28.57%). The average clozapine dose was 285.62 mg/day. VTE onset occurred within the first six months in 71.8% of the cases. Overall, 70.37% of the patients had comorbidities, and 87.5% had risk factors for VTE. In total, 68.57% were prescribed other medications at VTE onset, and 60% were being treated with another antipsychotic concomitantly. Finally, 32.5% of the patients died, while 67.5% survived. In 60% of the cases, clozapine was discontinued after VTE. In our literature review, we observed that among clozapine users, VTE occurred at a wide dose range, and most of the events occurred within the first six months. As many patients who are prescribed clozapine have risk factors for VTE, the risk should be considered at the time of prescribing. Further research should be conducted to elucidate the risk of VTE in clozapine users and the benefits of thromboprophylaxis.

Clozapine associated pulmonary embolism: systematic review

Background: Clozapine is a second-generation antipsychotic used in refractory schizophrenia. Clozapine can lead to pulmonary embolism (PE) by various mechanisms including immobility, weight gain and increased platelet aggregation.

Objectives: We performed a systematic review on published cases of PE associated with clozapine.

Methods: Comprehensive search of Medline, Embase and Cochrane library was done for relevant articles from inception until June 2017

Results: Total of 34 cases from 24 articles were included in the analysis. The mean age was 43.2 years with male predominance (63.6%). The mean dosage of clozapine was 281.4 mg daily. Duration of intake ranged from few days to many years. Nearly half of patients (47.82%) had no other co-morbidities for PE other than clozapine. For those reporting treatment, anticoagulation was chosen in 80%, thrombolysis in 10% and inferior vena cava filter placement in 5%. Mortality was 36.36% with three dying on presentation and an additional 9 dying during the follow-up period. Of the 18 patients in which follow-up data of clozapine were available, the drug was discontinued in 14 patients.

Conclusion: PE can occur at doses lower than usual dose of clozapine (300 mg daily). It is important to consider this association especially in patients with no other risk factors for PE.

Risk of venous thromboembolism due to antipsychotic drug therapy

An increasing number of reports suggest a link between venous thromboembolism (VTE) and the use of antipsychotics. To better understand this association the available body of evidence has been critically scrutinised. Relevant articles were identified in the databases Scopus and PubMed. Several observational studies using different methodologies show an increased risk of VTE in psychiatric patients. This elevated risk seems to be related to the use of antipsychotic medication and in particular to the use of clozapine and low-potency first-generation drugs. Many studies investigating the association have, however, methodological limitations. The biological mechanisms involved in the pathogenesis of this possible adverse reaction are largely unknown but several hypotheses have been suggested such as drug-induced sedation, obesity, increased levels of antiphospholipid antibodies, enhanced platelet aggregation, hyperhomocysteinemia and hyperprolactinemia. The association may also be related to underlying risk factors present in psychotic patients. Physicians need to be aware of this possible adverse drug reaction. Although supporting evidence has not been published they should consider discontinuing or switching the antipsychotic treatment in patients experiencing VTE. In addition, although data is lacking, the threshold for considering prophylactic antithrombotic treatment should be low when risk situations for VTE arise, such as immobilisation, surgery and so on.