WEDNESDAY, Sept. 24, 2014 (HealthDay News) -- People who use painkillers called nonsteroidal anti-inflammatory drugs (NSAIDs) -- which include aspirin, naproxen (Aleve) and ibuprofen (Advil, Motrin) -- may be at increased risk for potentially deadly blood clots, a new study suggests.
But the study only showed an association between use of the painkillers and higher clotting risk; it did not prove cause-and-effect.
The researchers analyzed the results of six studies involving more than 21,000 cases of a type of blood clot called a venous thromboembolism (VTE).
These clots include deep vein thrombosis (a clot in the leg) and pulmonary embolism (a clot in the lungs).
Reporting online Sept. 24 in Rheumatology, the analysis found that people who used NSAIDs had an 80 percent higher risk for venous clots.
"Our results show a statistically significant increased VTE risk among NSAID users. Why NSAIDs may increase the risk of VTE is unclear," study lead author Patompong Ungprasert, of Bassett Medical Center in Cooperstown, N.Y., said in a journal news release.
"Physicians should be aware of this association and NSAIDs should be prescribed with caution, especially in patients already at a higher risk of VTE," the researcher added.
Ungprasert noted that all types of NSAIDs were evaluated as one group, but not all types of NSAIDs may boost the risk of VTE.
Two experts said the findings are in keeping with prior research.
"It is not entirely surprising that NSAIDs are again implicated in causing clot-related illness," said Dr. Steven Carsons, chief of the division of rheumatology, allergy and immunology at Winthrop-University Hospital in Mineola, N.Y.
He pointed to the case of Vioxx, a powerful NSAID painkiller that was withdrawn from the market in 2004, after studies found a higher risk of heart attack and stroke in users.
The new study "makes a compelling case for further study and clinical surveillance for venous clotting events in those patients taking NSAIDs," Carsons said. However, he stressed that the study could not pinpoint which types of NSAIDs might pose the greatest risk, or which type of patients might be most vulnerable.
According to Carsons, "aspirin, the 'original' NSAID, has sufficient anti-clotting properties to be effective for prevention of VTEs, and most studies show that naproxen (Aleve) -- a common prescribed and over-the-counter NSAID -- carries no additional clotting risk."
Dr. Suzanne Steinbaum is a preventive cardiologist at Lenox Hill Hospital in New York City. She said that "without discerning which NSAIDS are more safe than others, this study shows the potential increase in VTE. It is important that both physicians and patients understand this risk, especially for those people who are already at risk for VTE."
The American Academy of Family Physicians has more about deep vein thrombosis.