A new study suggests the combination of some blood thinners and some antidepressants might not be such a good idea for cardiac patients.

The study says heart attack patients who are taking blood thinners plus selective serotonin reuptake inhibitors (SSRIs) for depression appear to be at higher risk of experiencing bleeds.

Blood thinners are generally prescribed to patients who have had heart attacks to reduce the likelihood of another attack; depression is quite common after a heart attack and patients with the mood disorder are most often prescribed an SSRI. (According to some estimates, up to 20 per cent of patients with cardiovascular disease experience depression.)

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But SSRIs, carry a risk of bleeding for users and combining them with other blood thinners like Aspirin or the drug clopidogrel raises the risk significantly.

The study, led by Christopher Labos of McGill University in Montreal, was published Monday in the Canadian Medical Association Journal.

The researchers looked at the records of more than 27,000 patients aged 50 and over between 1997 and 2007, and found taking an SSRI and Aspirin increased risk of a bleed by 42 per cent. And taking an SSRI with combined blood thinning therapy – Aspirin plus clopidogrel – pushed the risk up to 57 per cent.

The type of bleeding events the study refers to are things like bleeding stomach ulcers, a hemorrhagic stroke or other bleeds that required hospitalization or occurred during treatment in a medical institution.

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The authors say doctors should exercise caution when prescribing these two types of drugs for cardiac patients, and should weigh the benefits of SSRIs for depression in these patients against the increased risk of bleeding.

"Ultimately clinicians must weigh the benefits of SSRI therapy against the risks of bleeding in patients with major depression following acute myocardial infarction (a heart attack)," the researchers write in their study.

The Canadian Press