Certain types of antidepressants may not work as well in people who take non-steroidal anti-inflammatory drugs (NSAIDs), suggests a new study published online in the Proceedings of the National Academy of Sciences.

"This is certainly something that clinicians and individuals should be keeping in mind," Dr. Jennifer Warner-Schmidt, the study's lead author from The Rockefeller University in New York City, told Reuters Health.

Dr. Warner-Schmidt and her colleagues found that mice treated with the selective serotonin reuptake inhibitor (SSRI) Celexa (citalopram) and an NSAID had lower levels of the antidepressant in their blood than those that were only given Celexa.

Mice that were given a painkiller and antidepressant also did worse on tests measuring their stress and depression than those who just took the antidepressant.

The effect wasn't limited to rodents. The same researchers analyzed data from a previous study done on about 1,500 people treated with Celexa for 12 weeks. Those participants also reported on their use of NSAIDs during antidepressant treatment.

After those 12 weeks, 55% of patients who never took an NSAID during the study period were no longer depressed, compared to 45% of participants who said they took an NSAID at least once.

The researchers couldn't separate people who took an NSAID only once or twice during the 12 weeks from those who used them regularly.

Dr. Warner-Schmidt and her colleagues also didn't find that NSAIDs interfered with other, non-SSRI antidepressants.

Dr. Solomon Snyder, a neuroscientist at Johns Hopkins Medical School in Baltimore who will have a commentary coming out when the study appears in print, said in an email that the findings show that "if someone is receiving SSRIs, he/she should avoid NSAIDs."

However, he told Reuters Health, "Such a recommendation may well be controversial and cause difficulties for patients with arthritis and other conditions which benefit from NSAIDs."

The authors said that based on the data they used, it was impossible to prove that NSAIDs stop SSRIs from working. It's possible, for example, that people who have underlying conditions that require drugs such as aspirin and ibuprofen have more trouble recovering from depression.

However, Dr. Warner-Schmidt said, "The animal studies suggest there's a direct interaction between these two drugs."

Dr. Michael Thase, a psychiatrist from the University of Pennsylvania School of Medicine who was involved in the original research on humans cited by the authors, told Reuters Health that the new analysis is "intriguing," but that his data don't definitively support the animal studies.

However, Dr. Thase said, "Given how commonly the NSAIDs are used, this finding certainly needs to be followed up."

Dr. Warner-Schmidt added that it wasn't clear how the interaction between NSAIDs and SSRIs might be happening, and that future studies will need look more closely at that question.

Proc Natl Acad Sci USA 2011. Abstract

Genevra Pittman • Reuters Health Information © 2011