Researchers at Beth Israel Deaconess Medical Center, in Boston, and the Massachusetts Institute of Technology in Cambridge, have found that critically ill patients were more likely to die if they were taking the most commonly prescribed antidepressants when they were admitted to the intensive care unit (ICU).
The researchers conducted a retrospective study using the electronic medical records of 10,568 patients to look at in-hospital mortality and mortality a year after being admitted to the ICU.
"We found that mortality was higher overall for patients taking antidepressants prior to admission to the ICU and remained significantly higher a year later," said Katherine. M. Berg, MD, one of the physicians involved in the study. "We also found that certain subgroups of patients, particularly patients admitted for cardiac problems, appeared to be at even greater risk."
The study results will be presented at the ATS 2012 International Conference in San Francisco.
Of the 10,568 patient records studied, 1,876 patients were taking either a selective serotonin reuptake inhibitor (SSRI) or a serotonin and norepinephrine reuptake inhibitor (SNRI) prior to admission to an ICU. They were compared to patients admitted to an ICU who were not on one of these medications. After adjusting for age, gender, ICD-9 diagnosis, disease severity and co-morbidities, the researchers found that patients on SSRI/SNRI's prior to admission to the ICU were 73 percent more likely to die in the hospital (p<0.001), and that the increase in risk persisted at one year.
Among patient groups, risk was highest among patients with acute coronary syndrome and those who had undergone cardiac surgery. For both of these patient groups, the risk of dying in the hospital was more than double if they were taking one of these antidepressants prior to admission (OR 2.41; p<.0020 and 2.08; p<0.001, respectively).
Not all patient groups demonstrated that patients on SSRI/SNRI's were more likely to die. There was, for example, no increase in mortality among patients admitted with sepsis.
Both classes of antidepressants, which work by increasing the levels of neurotransmitters in the brain, are generally thought to have fewer side effects than previous generations of antidepressants. Recent studies, however, have found that SSRIs may increase a patient's risk of bleeding, dizziness, falls and stroke.
"Major depression is a common disorder affecting more than 16 percent of adults in the United States, and SSRI's are the most commonly prescribed medication class for this disease," added Dr. Berg. "The benefits of SSRI's for the treatment of depression are well documented. Due to the practical limitations of clinical trials, however, the long-term risks are unknown."
The researchers acknowledged that this study shows an association, but that the preadmission SSRI/SNRI use may not have been the cause of the increased mortality. The authors attempted to control for other factors that could lead to increased mortality, but were unable to control for some potentially important ones such as smoking and depression itself.
The authors stressed that these results require validation by similar studies utilizing other ICU databases. They stated, however, that this information highlights the need for alternative ways to monitor for potential adverse effects of medications, and the role that large clinical databases may play in this line of investigation.