Large Population-Based Study Confirms Increased Risk of VTE With Antipsychotics

The validity of the findings is strengthened by the large sample size and the low potential for exposure and outcome misclassification because of the detailed source of data and adjustment for a large number of confounders, according to Dr. Rosa Liperoti and Dr. Giovanni Gambassi.

It’s been demonstrated that “patients with schizophrenia have an increased risk of venous thromboembolism (VTE), and this might be associated with the use of antipsychotics, especially low-potency drugs such as chlorpromazine and thioridazine. So far, however, the possibility that the underlying psychiatric disorders themselves – and not the antipsychotics – are associated with VTE has never been excluded. This could occur, for example, by the increased concentrations of adrenaline seen during psychotic excitation increasing blood coagulation,” they noted.

In this study, in almost all cases the reason for prescription of antipsychotics could not be ascertained. Most of the antipsychotics used were conventional agents, with prochlorperazine – probably given for nausea and vomiting – accounting for almost 80% of all prescriptions, they wrote. “These findings indicate that VTE is directly linked to the use of an antipsychotic, and that the risk of VTE increases early after starting the drug.”

The implications are potentially far reaching. “Despite their association with serious risks and few data to support their efficacy, antipsychotics are widely used, and in 2008 they became the top selling drug class in the United States. Despite efforts to improve non–drug based interventions, antipsychotics are often used, especially for the treatment of agitation in people with dementia,” they wrote.

The findings suggest that physicians “need to be able to identify the best candidates for antipsychotic treatment, such as those people with the lowest vascular risk profile who may respond to short-term and low-dose treatment with antipsychotics because of individual pharmacogenetic characteristics, and those who may be more susceptible to developing side effects as a result of individual vascular risk factors possibly interacting with antipsychotics.”

Dr. Rosa Liperoti is a specialist in geriatrics and Dr. Giovanni Gambassi is a professor of geriatrics at Universit? Cattolica del Sacro Cuore in Rome. Both Dr. Liperoti and Dr. Gambassi reported that they have no relevant financial relationships. These comments were taken from a commentary that accompanied the study (BMJ 2010 Sept. 21[doi: 10.1136/bmj.c4216]).