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Aspirin Reduces Antidepressant Effectiveness

April 26, 2011

A recent US study suggests that aspirin and other anti-inflammatory drugs, including ibuprofen and naproxen, may reduce the effectiveness of the most widely used anti-depressant medications — selective serotonin reuptake inhibitors (SSRIs), reports AFP.

The finding, published this week in the online issue of the Proceedings of the National Academy of Sciences, may explain why many depressed patients taking SSRIs do not respond to antidepressant treatment.

Scientists at the Fisher Center for Alzheimer’s Disease Research at The Rockefeller University in New York City found that about one-third of people affected by major depressive disorders are resistant to anti-depressant drugs, which include big brand names such as Prozac, Paxil and Zoloft.

Researchers examined SSRIs when taken in combination with non-steroidal anti-inflammatory drugs (NSAIDs).

In the study, researchers treated mice with anti-depressants in both the presence and absence of NSAIDs. They then examined how the mice behaved in tasks that are sensitive to antidepressant treatment. The behavioral responses to antidepressants were inhibited by anti-inflammatory and analgesic treatments.

The researchers then confirmed these effects in humans, using data collected from the largest US study on anti-depressant use in humans — the STAR*D study of 4,000 adults over a seven year period. They found that depressed individuals who reported use of NSAIDs were much less likely to have their symptoms relieved by anti-depressants than depressed patients who did not use NSAIDs.

In the absence of use of NSAIDs, 54 percent of patients responded to anti-depressant use, whereas only about 40 percent responded to anti-depressant use while using NSAIDs.

“The mechanism underlying these effects is not yet clear. Nevertheless, our results may have profound implications for patients, given the very high treatment resistance rates for depressed individuals taking SSRIs,” said Jennifer Warner-Schmidt, a research associate at Paul Greengard’s Laboratory of Molecular and Cellular Neuroscience at Rockefeller University.

“Many elderly individuals suffering from depression also have arthritic or related diseases and as a consequence are taking both antidepressant and anti-inflammatory medications. Our results suggest that physicians should carefully balance the advantages and disadvantages of continuing anti-inflammatory therapy in patients being treated with antidepressant medications,” said Greengard, director of the Fisher Center for Alzheimer’s Disease Research at Rockefeller, and co-author of the study.

Depression in the elderly is also a risk factor for developing Alzheimer’s disease and researchers have suggested that treating depression in the elderly might reduce the risk of developing the disease.

It is known that depression is often found in patients with Alzheimer’s, but the implications of this discovery reach far beyond the 5.4 million Americans living with the disease. Clinical depression is one of the most commonly treated medical conditions, affecting nearly 19 million American adults — roughly 10 percent of the population. But some experts say that number is low, since depression often goes undiagnosed or untreated.

Over the past decade, antidepressants have become the most commonly prescribed drugs in the US, and are prescribed more than drugs to treat high blood pressure, cholesterol, asthma, or headaches, according to figures from the Centers for Disease Control and Prevention (CDC).

SSRIs ease the symptoms of depression by blocking the re-absorption of serotonin in the brain, which helps brain cells send and receive chemical messages and boosts your mood. These drugs help to correct chemical imbalances common in patients with depression. But according to Greengard and colleagues, that might be exactly why they become ineffective when used with NSAIDs.

Many patients end up switching anti-depressants due to a lack of effectiveness at some point during their treatment. This finding underscores one possible mechanism for medication failure, and it could help doctors to better counsel patients when it comes to considering secondary side effects of SSRIs.

Previous studies have suggested that NSAIDs may actually boost the potency of two other less-common types of anti-depressants, known as tricyclic or noradrenergic anti-depressants.

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