DOCTOR'S VIEW ARCHIVE
COX-2 Inhibitors Dilemma
Vioxx, Celebrex, Bextra What Patients Should Do
Medical Author:
William C. Shiel, Jr., MD, FACP, FACR
Medical Editor:
Jay W. Marks, MD
The recent withdrawal of Vioxx from the market
(September, 2004) has resulted in one of the most tumultuous times in history
for the pharmaceutical industry, patients, and doctors. At the time of its
withdrawal, Vioxx was one of the most widely used medications in the world. The
fallout has left the pharmaceutical industry on edge at a minimum, left patients
worried and wondering whom to trust, and left doctors out on a limb faced with
controversial research data to
review with their patients.
In this article, I hope to: (1) clarify issues by using
the current dilemma of the COX-2 inhibitor drugs [(rofecoxib) Vioxx, (celecoxib)
Celebrex, and (valdecoxib) Bextra] NOTE: April 7, 2005, Pfizer agreed to suspend sales and marketing of Bextra in the U.S., pending further discussions with the with the FDA. For more information, please read the
FDA press release.
, as a background; and (2) present general
guidelines as to what patients should do in response to having their medication
withdrawn from the market or even hearing of
potential risks of their medications that are reported in the media.
What's so special about COX-2 inhibitors?
COX-1
Cyclooxygenase-1 (COX-1) is an enzyme that is normally present in a
variety of areas of the body, including sites of inflammation and the stomach.
The COX-1 enzyme of the stomach produces certain chemical messengers (called
prostaglandins) that ensure the natural mucus lining, which protects the inner
stomach. Common anti-inflammatory drugs, like aspirin or ibuprofen, block the function of the
COX-1 enzyme along with another enzyme, COX-2 (described below). With these traditional antiinflammatory drugs, inflammation is reduced by blocking Cox-2, but the protective mucus lining of
the stomach is also reduced because Cox-1 is blocked, which can cause stomach upset, ulceration, and
bleeding from the stomach and intestines.
COX-2
Another enzyme, cyclooxygenase-2
(COX-2), also produces these chemical messenger molecules, but the COX-2 enzyme
is located specifically in areas of the body that are responsible for
inflammation and not in the stomach. When the COX-2 enzyme is blocked,
inflammation is reduced. Since the COX-2 enzyme does not play a role in the
normal function of the stomach, medications that selectively block COX-2 do not
present the risk of injuring the stomach that medications also blocking COX-1
can.
Newly developed drugs that selectively block the COX-2
enzyme are called COX-2 inhibitors. Blocking this enzyme impedes the production
of the prostaglandins that cause the pain and swelling of arthritis
inflammation. The common anti-inflammatory drugs (like aspirin, ibuprofen, and
naproxen) are all
non-selective and act by blocking the action of both the COX-1 and COX-2 enzymes.
The COX-2 inhibitors represent a newer class of
anti-inflammatory drugs that do not affect COX-1, but selectively block only
COX-2. This selective action provides the benefits of reducing inflammation
without the increased risk of stomach irritation, ulceration, and bleeding. A
major advantage of the COX-2
inhibitors over traditional non-selective COX-1 and COX-2 NSAIDs (nonsteroidal
anti-inflammatory drugs) lies in the fact that they are easier on the stomach.
Therefore, they are generally considered safer for patients with a history of
stomach (gastrointestinal) problems. Another
particular advantage of COX-2 inhibitors is that they do not impair the normal
function of an important blood
clotting element called platelets. As a result, they may be used in patients
taking blood thinning medications, such as warfarin (Coumadin), and they may be
used in and around surgical procedures without an increased risk of bleeding.
What Happened With Vioxx (rofecoxib)?
On September 30, 2004, Vioxx (rofecoxib), a drug used to quiet the inflammation of
arthritis and relieve pain, was withdrawn from the market by its maker, Merck.
The reason for the withdrawal was the occurrence of side effects noted in a
study that Merck was conducting to see if Vioxx could prevent polyps of the
colon and rectum. During this trial, it was
noted that there was an increased risk for heart attack and stroke in patients continuing to take Vioxx longer
than 18 months.
