Risk of Blood Clots Linked to Seroquel, Other Atypical Antipsychotics: Study

The use of newer atypical antipsychotic medications, such as Seroquel, Thorazine and Risperdal, has been associated with an overall increase in the risk of blood clots, according to British researchers.  

A new study published in the British Medical Journal looks at the rate of blood clots in people who are taking various antipsychotic drugs. The findings indicate that people who use any antipsychotics are at greater risk for venous thromboembolism, or blood clots, but the highest risk was associated with people who take atypical antipsychotics.

The researchers looked at clinical records of 115,000 people in the U.K. and found a 32% increased risk of blood clots among those that had been prescribed antipsychotics in the last two years. The risk increased to 56% for people who had been using the drugs as recently as the last three months, and patients who had been newly prescribed antipsychotics in the last three months were 97% more likely to suffer blood clots than people not taking the drugs.

The results of the study indicate that atypical antipsychotics, as a class, were more closely associated with blood clot risks than conventional antipsychotics. The findings also indicate that patients taking two or more different antipsychotics were at even more risk, with double the chance of suffering a blood clot than someone taking none of the drugs.

Side effects of Seroquel were associated with the highest risk, with users suffering blood clots at a nearly 3-to-1 ratio over people not taking any antipsychotics.

Seroquel (quetiapine fumarate) is an atypical-antipsychotic that is a top selling drug for AstraZeneca, generating nearly $5 billion a year in sales. Originally approved by the FDA in 1997 for the treatment of schizophrenia, it has been frequently prescribed off-label for uses that were not approved as safe and effective at the time, such as anxiety, obsessive dementia, compulsive disorders and autism.

AstraZeneca had faced about 22,500 Seroquel lawsuits from plaintiffs who claimed the drug caused diabetes and weight gain. However, the company has reached Seroquel settlements in the majority of those cases.

An editorial posted in connection with the study noted that the reason patients had been prescribed the atypical antipsychotics could not be determined in 99% of the cases. With one drug, prochlorperazine, scientists estimated that 80% of the prescriptions were for off-label uses, such as nausea and vomiting.