By: Steve Siwy for Knee1.comDrug company Pfizer Inc. said in a Dec. 17th press release that one of its studies has shown an increased risk of heart attack for patients taking Celebrex (Pfizer’s trademarked name for celecoxib), which like the recently-recalled Vioxx, is part of a class of painkillers known as cox-2 inhibitors. Merck recalled Vioxx when its own studies showed that the medication caused an increased risk of heart attack and stroke after 18 months of use.
The study that found the higher heart-attack risk was one of two long-term trials being conducted with the National Cancer Institute to investigate whether Celebrex might have cancer-prevention applications. In that study, called the Adenoma Prevention with Celecoxib (APC) trial, which gave participants daily 400mg to 800mg doses of Celebrex, those taking the drug showed 2.5 times the likelihood of having a major “cardiovascular event” than those taking the placebo, Pfizer said. In the other study, the Prevention of Spontaneuous Adenomatopus Polyps (Pre SAP) trial, which gave patients 400mg doses only, no increased risk was found. When the National Cancer Institute discovered the high heart-attack numbers in the APC trail, they suspended the study.
The implications for the future of Celebrex are unclear at this early stage, though Pfizer says it has no plans to recall the medication, citing the high doses in the APC study (the recommended dose of Celebrex for treating arthritis is 100mg to 400mg), and numerous previous studies it has done which have not shown any heart risks, including the other study in the trials. Coming as it does on the heels of the Vioxx recall, however, some doctors and their patients prefer to err on the side of caution. Dr. Richard Hayes, for instance, who practices cardiology at New York University, said in a Reuters article, “This raises my concern about Celebrex and all the cox-2 inhibitors, so I will no longer be prescribing any of them.”
The Food and Drug Administration, according to statement also released on Dec. 17th, said that it had asked Pfizer to withdraw consumer advertising for Celebrex in light of what it called “new and conflicting scientific data,” and to change the information that the company provides to doctors to reflect FDA recommendations that doctors seek alternatives to Celebrex for their patients whenever possible. Pfizer, says the FDA, has agreed to both requests. Bextra, another cox-2 inhibitor made by Pfizer, had already been slated to receive a warning label, after another study had shown it to be risky for patients who had undergone coronary bypass surgery.
Nonsteroidal anti-inflammatory drugs (NSAIDs), the class to which cox-2 inhibitors belong, work by blocking cyclooxygenaxe, known as cox. The kind of cyclooxygenase known as cox-1 protects the stomach, which is why NSAIDs tend to cause gastrointestinal problems as they block both kinds of cox. Cox-2 inhibitors, by blocking less of the cox-1 type of cyclooxygenase, tend to cause fewer stomach problems in patients than traditional over-the-counter NSAIDs like ibuprofen or acetaminophen. However, the inhibition of cyclooxygenase also reduces prostaglandin levels in the body. Prostaglandin is a kind of lipid vital to the process of causing pain and inflammation, and also, in the case of this particular prostaglandin, to protecting the cardiovascular system from a different, damaging type of prostaglandin. This, according to some studies, is the mechanism by which cox-2 inhibitors can make the cardiovascular system more vulnerable to malfunction.
