COX-2 inhibitors are a subclass of nonsteroidal antiinflammatory drugs (NSAIDs). NSAIDs work by reducing the production of prostaglandins, chemicals that promote inflammation, pain, and fever. Prostaglandins also protect the lining of the stomach and intestines from the damaging effects of acid, promote blood clotting by activating platelets, and also affect kidney function.
The enzymes that produce prostaglandins are called cyclooxygenase (COX). There are two types of COX enzymes, COX-1 and COX-2. Both enzymes produce prostaglandins that promote inflammation, pain, and fever; however, only COX-1 produces prostaglandins that activate platelets and protect the stomach and intestinal lining.
NSAIDs block the COX enzymes and reduce production of prostaglandins. Therefore, inflammation, pain, and fever are reduced by all COX inhibitors. Since the prostaglandins that protect the stomach and promote blood clotting also are reduced, NSAIDs can cause ulcers in the stomach and intestines, and increase the risk of bleeding. Unlike older NSAIDs that block both COX-1 and COX-2, the newer COX-2 inhibitors only block the COX-2 enzyme. Since COX-2 inhibitors do not block COX-1 (which primarily produces prostaglandins that protect the stomach and promote blood clotting) they do not cause ulcers or increase the risk of bleeding as much as the older NSAIDs. Nevertheless, COX-2 inhibitors are as effective as the older NSAIDs for treating inflammation, pain and fever.
For what conditions are COX-2 inhibitors used?
COX-2 inhibitors are used for treating conditions that cause inflammation, mild to moderate pain, and fever. Examples include:
- sports injuries,
- rheumatoid arthritis,
- colorectal polyps, and
- menstrual cramps.
Unlike aspirin, also an NSAID, they are not effective for preventingstrokes and heart attacks in individuals at high risk for such events.
Are there any differences among the different types of COX-2 inhibitors?
Celecoxib is the only COX-2 inhibitor currently available in the United States. Rofecoxib (Vioxx) and valdecoxib (Bextra) are no longer available because they increased the risk of heart attacks and strokes with long term use. Rofecoxib was discontinued in 2004 and valdecoxib was discontinued in 2005.
What are the side effects of COX-2 inhibitors?
Common side effects include:
- abdominal pain,
- flatulence, and
Other side effects include:
- kidney failure,
- aggravation of hypertension,
- ringing in the ears,
- blurred vision,
- light sensitivity,
- weight gain,
- water retention,
- drowsiness, and
Allergic reactions also can occur. Individuals who have developed allergic reactions (rash, itching, difficulty breathing) from sulfonamides [for example, trimethoprim and sulfamethoxazole Bactrim)], aspirin or other NSAIDs may experience an allergic reaction to celecoxib and should not take celecoxib.
COX-2 inhibitors and other NSAIDs may increase the risk of heart attacks, stroke, and related conditions, which can be fatal. This risk may increase with duration of use and in patients who have underlying risk factors for disease of the heart and blood vessels. NSAIDs should not be used for the treatment of pain resulting from coronary artery bypass graft (CABG) surgery.
Other NSAIDs and, to a lesser extent, COX-2 inhibitors may increase the risk of serious, even fatal, stomach and intestinal adverse reactions such as bleeding, ulcers, and perforation of the stomach or intestines. These events can occur at any time during treatment and without warning symptoms. Elderly patients are at greater risk for these types of reactions.
With which drugs do COX-2 inhibitors interact?
Concomitant use of celecoxib with aspirin or other NSAIDs [for example,ibuprofen, naproxen (Naprosyn,Naprelan), etc.) may increase the occurrence of stomach and intestinal ulcers. It may be used with low dose aspirin.
Alcohol consumption increases the risk of developing stomach ulcers when taking NSAIDs; this may also apply to celecoxib.
Fluconazole (Diflucan) increases the concentration of celecoxib (Celebrex) in the body by inhibiting the elimination of celecoxib in the liver.
Celecoxib (Celebrex) increases the concentration of lithium (Eskalith) in the blood by 17% and may increase the blood thinning effect of warfarin (Coumadin).
Which COX-2 inhibitors are available?
Celecoxib (Celebrex) is the only COX-2 inhibitor available in the United States.