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HAMILTON, Ontario, Nov. 1 - Taking high doses of Advil or Motrin (ibuprofen) even for a few days can significantly increase the risk of gastrointestinal bleeding, researchers reported today.

After three days of treatment with 800 mg of ibuprofen three times a day, healthy men had evidence of significant blood loss compared with men randomized to placebo (P<0.001).

The volume of fecal blood loss was 3.64 mL greater in the ibuprofen group, Richard Hunt, M.D., of McMaster University here and colleagues reported in the November issue of Clinical Gastroenterology and Hepatology.

Dr. Hunt said the finding is somewhat surprising because ibuprofen is generally considered the safest of the non-steroidal anti-inflammatory drugs (NSAIDs) in terms of bleeding risk.

The authors conducted a post-hoc analysis of two small, single- center, randomized studies, with 68 participants. They defined fecal blood loss as significant when it was more than 2 mL daily. Fecal blood loss was measured by radioactive analysis of chromium-51 labeled red cells in stools during baseline and throughout the study for four weeks of treatment. At baseline fecal blood loss averaged 0.36 mL for all participants.

During the study, volunteers randomized to ibuprofen had an average fecal blood loss of more than 2 mL, with a daily mean loss of 2.55 mL versus 0.7 mL in the placebo arm (P<0.001).

Twenty-six of 31 participants randomized to ibuprofen had between one and seven episodes of microbleeding with fecal blood loss of more than 3 mL. Nine men in the ibuprofen arm had a maximum fecal blood loss of more than 10 mL and in two men the fecal blood loss volume reached 73 mL and 66 mL respectively.

Dr. Hunt noted that the study dose was significantly higher than the approved over-the-counter dose of ibuprofen, which is 1,200 mg daily. But he said that people who regularly use ibuprofen often use it to treat chronic pain, such as arthritis pain. Such patients "often increase the recommended dose of their painkillers."

The authors concluded that "the potential for a serious GI complication should still be considered when ibuprofen is recommended for self-medication."

In an editorial that accompanied the paper, Denis M. McCarthy, M.D., Ph.D, of the University of New Mexico pointed out that although the authors didn't investigate the development of anemia, "it is reasonable to assume that blood loss that continues at this rate in long term NSAID users could lead to significant anemia at least in some patients."