Patients who take a popular form of antidepressants are at risk of abnormal bleeding, according to a new study. The drugs, known as selective serotonin reuptake inhibitors, or SSRIs, interfere with clotting and can provoke bleeding in the stomach, the vagina and even the brain, researchers found.
The research, published in this week's edition of the Archives of Internal Medicine, noted that, ironically, the better the drugs work, the greater the risk of bleeding.
SSRIs include fluoxetine (sold under the brand name Prozac) and paroxetine (Paxil). They work by stimulating production of the brain chemical serotonin, which is believed to regulate depression and anxiety. But serotonin also helps regulate blood clotting.
"We found a significant association between [the] degree of serotonin-reuptake inhibition by antidepressants, and risk of hospital admission for abnormal bleeding," said Welmoed Meijer, a pharmacoepidemiologist at the Utrecht Institute for Pharmaceutical Sciences in the Netherlands.
The study was conducted on a group of 64,000 antidepressant users between 1992 and 2000. Individuals were classified according to the degree (high, intermediate, or low) of serotonin-reuptake inhibition of the antidepressants they were taking.
Among study participants, there were 196 cases of abnormal bleeding -- including abnormal uterus bleeding and gastrointestinal bleeding.
"We found a significant association between degree of serotonin reuptake inhibition by antidepressants and risk of hospital admission for abnormal bleeding," the researchers wrote.
Dr. Meijer said that while very few patients actually experienced the side effects, it is significant that patients who took SSRIs were three times more likely to suffer from bleeding than those who took other kinds of antidepressants.
He said bleeding incidents were far more severe in people taking non-steroidal anti-inflammatory drugs, which range from over-the-counter products such as acetylsalicylic acid (Aspirin), ibuprofen (Advil, Motrin) prescription drugs such as rofecoxib (Vioxx) and celecoxib (Celebrex), because those commonly used drugs also affect clotting.
Dr. Meijer said the study almost certainly underestimated bleeding because it looked only at hospital admissions. The practical information physicians and consumers should retain, he said, is that SSRIs may not be appropriate for some people, particularly those who have blood disorders such as hemophilia or anemia, those who have ulcers, and women who suffer from heavy menstrual bleeding.
SSRIs have been in the news of late because of reports that use of the antidepressants may actually increase the risk of suicide, particularly among children and adolescents.
Health Canada has warned that pregnant women should avoid taking a broad range of antidepressants, including SSRIs. It also cautioned that children and adolescents taking SSRIs should be monitored, particularly for suicidal thoughts.
According to IMS Canada, a company that tracks prescription-drug trends, there were 15.7 million prescriptions last year for SSRIs. Sales topped $990-million in 2003. Paxil alone has sales of more than $280-million a year.
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