The only type of selective cyclo–oxygenase-2 (COX–2) inhibitor currently approved for sale in the United States is celecoxib (Celebrex). Despite the potential benefits of using this drug for certain conditions, such as arthritis, serious side effects may occur. Sometimes side effects can happen without any warning, although warning symptoms often occur. A physician should be notified if a patient experiences any of the following:

• Fainting
• Trouble breathing or swallowing
• Rapid heartbeat (tachycardia)
• Swelling of the face, fingers, feet or lower legs
• Intense abdominal pain or nausea
• Black stools
• Vomiting of blood or substance similar in appearance to coffee grounds
• Unusual weight gain
• Rash, hives, blisters or itchiness
• Fever
• Mouth sores
• Drowsiness or fatigue
• Back pain
• Jaundice
• Painful urination (dysuria)

Because celecoxib has been available for only a short time, long-term side effects have only recently begun to be documented and understood.  A physician can assess a patient’s individual risk for certain complications.

In 2004, the COX–2 inhibitor rofecoxib (Vioxx) was voluntarily withdrawn from the market by its manufacturer after studies linked the drug to high blood pressure and increased risk of heart attack and stroke. The U.S. Food and Drug Administration (FDA) found that people who regularly took standard doses of the drug had a 50 percent higher chance of heart attack or sudden cardiac death than patients taking celecoxib.

Another COX–2 inhibitor, valdecoxib (Bextra), was voluntarily withdrawn for sale in the United States by its manufacturer in 2005 because of evidence that the drug may be associated with an increased risk for heart attack, stroke and serious skin reactions. Research is investigating whether the benefits of the drug outweigh these potential risks in some instances, such as treatment and prevention of cancer.

Other COX–2 inhibitors and some traditional nonsteroidal anti–inflammatory drugs (NSAIDs) may also pose similar risks for serious skin reactions. However, the risk of valdecoxib causing these effects appears to be much greater in comparison to the traditional drugs.  

Research has also linked the use of celecoxib and other COX–2 inhibitors to additional serious side effects, including:

• Stomach ache, diarrhea and headache. These are the most common side effects reported by people who take COX–2 inhibitors.
  
  
• Gastrointestinal problems. COX–2 inhibitors in rare cases can cause bleeding in the stomach or intestines. The risk increases if alcohol is consumed daily or in excess. In rare cases, blockage or perforation of the intestines may occur.
  
  
• Kidney or liver problems. Patients taking COX–2 inhibitors rarely experience problems with the kidney or liver. Blood may be monitored routinely by a physician to check for signs of kidney or liver damage in patients who commonly use these drugs.
  
  
• Aseptic meningitis. In rare instances, rofecoxib can cause this nonbacterial form of meningitis. Aseptic meningitis requires hospitalization, but is typically not life threatening in individuals with normal immune systems. Individuals with autoimmune diseases (e.g., lupus) have a higher risk of contracting aseptic meningitis when taking rofecoxib.
  
  
• Anaphylaxis. This is a rare but very serious allergic reaction that may occur in people allergic to aspirin, other NSAIDs or certain antibiotics (e.g., sulfonamides).