Antipsychotics slightly raise risk for blood clots

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Antipsychotics or medications that are used to treat psychiatric illnesses such as schizophrenia and bipolar disorder are reported to raise the risk of dangerous blood clots.

The study that established this link compared their use in over 25,000 people with blood clots in their legs or lungs and in almost 90,000 people who did not have clots. Results showed that there was a 32% increase in risk of a blood clot in people currently using antipsychotics. However, the overall risk of having a blood clot was still very small, even among people taking antipsychotics. Overall, people in the study had about a 0.1% chance of having a blood clot each year. Those taking newer “atypical” antipsychotics had 73% more chance of developing a clot, compared with a 28% increase for other types of antipsychotic.

The study was conducted by researchers from Nottinghamshire County Teaching Primary Care Trust led by Professor Julia Hippisley-Cox and was published in the peer-reviewed British Medical Journal. The researchers used data from the UK QResearch primary care database, which holds anonymous medical records on over 11 million people who registered at one of 525 GP practices in the UK over the past 16 years. Adults aged 16 to 100 years old who were registered with participating practices between 1996 and 2007 were included.

The researchers identified people who were recorded as having a first blood clot (venous thromboembolism) between 1996 and 2007 (the cases). There were four controls for each of these cases that matched in age, sex and other parameters but did not have blood clots. They then compared past use of antipsychotics between cases and controls. In total 25,532 eligible cases were identified and 89,491 matched controls selected from the database. Cases had either a deep vein thrombosis (15,975 people) or a blood clot in their lungs (pulmonary embolism, 9,557 people). Other factors like obesity, smoking etc. were also taken into account.

Writing in the BMJ, Professor Giovanni Gambassi and Dr Rosa Liperoti, from the Centro di Medicina dell'Invecchiamento in Rome said it was important for doctors to identify those patients at highest risk of side-effects. Dr Sharlin Ahmed, from the Stroke Association pointed out that there have been studies that revealed a higher stroke risk among patients taking antipsychotics. “Although the overall risk of a stroke is low, the results of this study remind us that antipsychotics are powerful drugs and should be prescribed carefully, with regular follow-ups,” she said.

GPC prescribing lead Dr Bill Beeby added, “The study was retrospective and finished three years ago and the results need to be verified so it won't promote massive change…But it should raise our index of suspicion in patients with deep vein thrombosis or pulmonary embolism. We need to look at our use of antipsychotics full stop. Part of the problem is their increased use for non-psychosis. As a result of extending the range of patients we are extending the risks of side effects…I don't think most GPs initiate these treatments but they are increasingly initiated in secondary care - for good clinical reasons - and tend to fall back into general practice.”

Experts however warn that people taking antipsychotics should not be concerned by this news and should not stop using their medication. Any concerns raised by this news can be discussed with a doctor.

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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