Some popular antidepressant drugs can cause internal bleeding similar to that triggered by aspirin and related painkillers, researchers said on Monday.

The anti-depressants involved are Prozac-type Selective Serotonin Reuptake Inhibitors, or SSRIs, the report from the Northwestern University Medical School said.

A review of the medical records of 549 patients admitted to hospitals for acute gastrointestinal bleeding found that ongoing use of such antidepressants caused a risk of bleeding similar to that caused by the regular use of non-steroidal anti-inflammatory drugs, or NSAIDs, such as aspirin, ibuprofen and naproxen.

“While more research needs to be conducted ... physicians must closely monitor for this serious adverse event, especially in patients who are taking both SSRIs and NSAIDs,” said Dr. Michael Jones, the report’s chief author.

“This is a potent example of the need for doctors to be particularly conscious about potential side effects when prescribing multiple medications for their patients,” he added.

The study was released in Chicago during an annual meeting of gastrointestinal experts. It was sponsored by TAP Pharmaceuticals, a U.S. joint venture of Japan’s Takeda Pharmaceutical Co. Ltd. and Abbott Laboratories Inc. The company makes Prevacid, a heartburn drug.

Eli Lilly and Co., which makes Prozac, said the possibility of bleeding was already listed as a potential side effect of the drug and users were cautioned about it in information provided with the product. Monday’s study named no specific brands.

Gastrointestinal bleeding from NSAIDs has been blamed for 16,000 deaths a year in the United States, and that problem helped spur the development of COX-2 drugs, which were designed to be a safer replacement.

But the COX-2 drugs were found to raise the risk of heart attacks and strokes. Two - Pfizer Inc.‘s Bextra and Merck & Co.‘s Vioxx - have been pulled from the market.

The U.S. Food and Drug Administration also asked Pfizer to include a strong “black box” warning for its COX-2 Celebrex.