Cyclooxygenase 2 Inhibitors

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Cyclooxygenase 2 inhibitors

Definition

Cyclooxygenase 2 inhibitors, also known as COX-2 inhibitors, are useful as pain and antiflammatory medications for cancer patients. COX-2 inhibitors are not better at stopping pain and inflammation than other nonsteroidal anti-inflammatory drugs (NSAIDs), but are less likely to cause stomach ulcers and bleeding.

Purpose

Nonsteroidal anti-inflammatory drugs (NSAIDs) used to treat pain and inflammation are relatively effective in controlling these symptoms but can cause serious side effects. These side effects include stomach ulcers, kidney problems, and increased likelihood of bleeding. Aspirin is the most serious offender, although other pain medications in the NSAID class of medication present similar problems. COX-2 inhibitors were developed as a type of pain medication less likely to cause stomach and bleeding problems than existing NSAID pain medications.

Description

Cyclooxygenase is a chemical important for the normal functioning of the human body. Cyclooxygenase helps the stomach and kidneys to function normally, the platelets in the blood to function normally, and the brain to regulate body temperature and feel pain. Scientists have discovered that there are two distinct types of cyclooxygenase (abbreviated COX). These two types of COX are known as COX-1 and COX-2. COX-1 is needed to maintain the normal body functions of platelet aggregation, the regulation of blood flow in the kidney and stomach, and the regulation of gastric acid secretion in the stomach.

COX-2 is produced only when the body's tissues have been injured. COX-2 mediates inflammation, helps the nerves feel pain, and helps the brain regulate fever . A medication that inhibits COX-2 can suppress inflammation, relieve pain, and reduce fever. Inhibition of COX-1, on the other hand, results in bleeding and kidney and stomach toxicity.

The problem with many older pain medications is that they affect both COX-1 and COX-2, even though they provid benefit only through how they affect COX-2. That is why their long-term use may be associated with such side effects as stomach ulcers, decreased kidney function, and a tendency for excessive bleeding. COX-2 inhibitors inhibit COX-2 while exerting less effect on COX-1.

As of 2001, two COX-2 inhibitors are available by prescription in the United States. Celecoxib (brand name Celebrex) was the first to be available, followed by rofecoxib (brand name Vioxx).

Recommended dosage

Celecoxib comes in 100 mg and 200 mg capsules that are taken orally either once or twice a day.

Rofecoxib comes in 12.5, 25, and 50 mg tablets for oral use. In addition, it comes in 12.5 mg per 5 milliliter and 25 mg per 5 milliliter liquid doses. Both tablets and liquid are taken orally once a day.

Precautions

Celecoxib should not be taken by patients with sulfonamide allergy. This medication should not be taken during the last few months of pregnancy.

Rofecoxib is safe for patients who are allergic to sulfonamides. It should not be taken during the last few months of pregnancy.

Side effects

Celecoxib has few side effects. A small number of patients report stomach upset and even fewer report abdominal pain. Other effects reported rarely with celecoxib include kidney problems, fluid retention, and retention of water in the tissues. The occurrence of ulcers in patients taking celecoxib is less frequent than for many other pain medications. However, the long-term safety of celecoxib has not been well-researched.

Rofecoxib may cause diarrhea , dyspepsia, and abdominal pain. More rarely, headache, kidney problems, high blood pressure, anemia , respiratory infections, and retention of water in the legs is seen. The occurrence of ulcers in patients taking rofecoxib is less frequent than for many other pain medications. However, the long-term safety of rofecoxib has not been well-researched.

Interactions

Celecoxib may affect the activities of warfarin , a medication that limits the ability of blood to clot. Celecoxib may also be involved in interactions with: furosemide, a diuretic; angiotensin-converting enzyme inhibitors (ACE inhibitors), medicines used for high blood pressure and some heart problems; lithium, a medication for bipolar disorder; and fluconazole, an antifungal medication. Celecoxib may be taken with any of the medicines mentioned above—however, the doctor should closely monitor these drug combinations. Because celecoxib is a relatively new medication, more remains to be learned about its potential to interact with other drugs.

Rofecoxib may interact with the anti-tuberculosis medication rifampin. It may also be involved in interactions with lithium, ACE inhibitors, warfarin, and methotrexate , a medication used for cancer and arthritis. Rofecoxib may be taken with any of the medicines mentioned above—again, however, the doctor should closely monitor these drug combinations. Because rofecoxib is a relatively new medication, more remains to be learned about its potential to interact with other drugs.

Bob Kirsch