Celebrex (celecoxib)New Treatment for Arthritis
By Rebecca Hilgen Bryan, MSN, RN, NPC
Celebrex (G.D. Searle & Co.) is a cyclooxygenase-2 (COX-2) inhibitor used in the treatment of osteoarthritis and rheumatoid arthritis. While it falls into the category of non-steroidal anti-inflammatory drugs (NSAIDs), the most common class of agents used to treat the pain and inflammation of arthritis, Celebrex is the first of its kind to inhibit only COX-2 and not COX-1. This is significant because all other NSAIDs inhibit both, and COX-1 plays an important role in maintaining normal gastrointestinal and platelet function.
To date, the anti-inflammatory and analgesic benefits of NSAID therapy have been hampered by the significantly increased risk of GI ulceration and bleeding. The introduction of Celebrex to the market is so important because it inhibits only COX-2 and not COX-1, so pain and inflammation are effectively reduced while the risk of GI ulceration and bleeding is markedly decreased.
In clinical studies, Celebrex has demonstrated significant reduction in joint pain in osteoarthritis, and in joint tenderness/pain and swelling in rheumatoid arthritis, when compared to placebo. At doses of 100 mg to 200 mg twice daily, Celebrex was shown to be similar in effectiveness to naproxen 500 mg BID, a commonly prescribed NSAID. In osteoarthritis, there was no increased benefit of 200 mg BID when compared to 100 mg BID. In rheumatoid arthritis, some patients derived additional benefit from the 200 mg BID dose. There was no increase in benefit for osteo- or rheumatoid arthritis from doses greater than 200 mg BID.
Special clinical studies were performed to assess the gastrointestinal adverse effects of Celebrex. Upper GI endoscopic evaluations were performed on more than 4,500 arthritis patients who were enrolled in five controlled randomized 12-24 week trials. Celebrex was tested against two commonly prescribed NSAIDs, naproxen and ibuprofen, and it was associated with statistically significant lower incidence of endoscopic ulcers over the study period. There was no consistent relationship between the incidence of gastroduodenal ulcers and the dose of Celebrex over the range studied (50 mg 400 mg). Risk of ulceration was higher in those patients on Celebrex who also took aspirin, though still less than those patients on naproxen and ibuprofen.
Celebrex was studied for its effect on platelet aggregation and bleeding time. At single doses up to 800 mg and multiple doses of 600 mg BID for up to seven days duration, there was no effect on platelets. In contrast, naproxen 500 mg BID, ibuprofen 800 mg TID, and diclofenac 75 mg BID significantly reduced platelet aggregation and prolonged bleeding time.
Celebrex is available in two formulations: 100 mg and 200 mg capsules. For osteoarthritis, dosing is 200 mg per day, dosed either once or twice a day. For rheumatoid arthritis dosing is BID, using either 100 mg or 200 mg capsules. While Celebrex can be administered without regard to meals, onset of action is faster if taken on an empty stomach. Once swallowed, peak plasma levels are reached in approximately three hours.
Celebrex is metabolized in the liver by the cytochrome P450 2C9 system. The three metabolites produced are inactive as COX-1 or COX-2 inhibitors. This drug is eliminated predominantly by hepatic metabolism with the metabolites excreted in urine and feces. Celebrex is highly protein bound, primarily to albumin, and is extensively distributed into the tissues.
The pharmacokinetics of this drug were studied in a number of special populations. In geriatric patients, higher levels of Celebrex were found, and though dose adjustment is not generally necessary, using the lowest recommended dose was suggested in those patients weighing less than 50 kg (around 110 pounds). When race was studied, an increase in total absorption of Celebrex was found in blacks as compared to Caucasians. The cause and the clinical significance of this finding are unknown. Doses need to be reduced for patients with mild to moderate hepatic insufficiency; patients with severe hepatic insufficiency have not been studied. Patients with renal insufficiency were found to have a lower total absorption of Celebrex when compared to patients with normal renal function. Patients with severe renal impairment were not studied. Celebrex capsules have not been studied in patients less than 18 years of age.
Drug interactions may be significant when Celebrex is administered with drugs that inhibit the cytochrome P450 2C9 system, such as lithium or fluconazole. Celebrex itself is not an inhibitor of cytochrome P450 2C9, 2C19 or 3A4 systems. Clinical studies have identified significant interactions with lithium and fluconazole. Experience with NSAIDs suggests the potential for interactions with furosemide and ACE inhibitors. Celebrex was studied with glyburide, ketoconazole, methotrexate, phenytoin, tolbutamide and warfarin in vivo and clinically important interactions have not been found.
Precautions for Celebrex include use of this drug in patients with hepatic insufficiency, severe renal insufficiency, and in patients with fluid retention, hypertension or heart failure. Patients with aspirin-sensitive asthma should not be prescribed Celebrex. This drug, just as with all NSAIDs, cannot be expected to substitute for corticosteroids or be used to treat corticosteroid insufficiency. Abrupt discontinuation of corticosteroids may lead to exacerbation of corticosteroid-responsive illness. Serious GI bleeding has occurred, with or without symptoms, in patients who have been prescribed NSAIDs. While it is hoped that Celebrex will have a markedly reduced incidence of GI bleed, it is unclear at this time what the risk is. Therefore, patients need to be prescribed the lowest dose possible for the shortest amount of time possible and be monitored for signs of GI bleed. Patients on warfarin were studied and no effect was noted when taking Celebrex; however, these patients need to be monitored because of their overall increase in risk of bleeding complications.
CONTRAINDICATIONS AND SIDE EFFECTS
Contraindications include known hypersensitivity to Celebrex, demonstrated allergic-type reactions to sulfonamides (such as Bactrim, Roche Laboratories), and known aspirin (or other NSAID)-sensitive asthma.
Side effects in patients on Celebrex were low. More than 8,500 patients have been studied and have taken Celebrex for between six months and two years. The most common side effects were dyspepsia, diarrhea and abdominal pain; there was a low incidence of peripheral edema.
Since Celebrex is a new prescription medicine designed to relieve pain and inflammation that accompanies arthritis, patient education is important. Patients should be informed that although Celebrex can be taken without regard to meals, it will work faster if taken on an empty stomach. They should be warned to report if they are allergic to sulfonamides or if they have had an asthma reaction when taking aspirin or other NSAIDs.
Inform your patients that Celebrex is not a substitute for aspirin for prevention of heart attack or stroke. Finally, they should be aware that though Celebrex is expected to have a lower incidence of stomach ulceration and bleeding, serious ulcers could occur without warning symptoms. Therefore, they should remain alert to any signs and symptoms of stomach bleeding.
Rebecca Hilgen Bryan is an adult nurse practitioner at Wolfe-Simon Medical Associates, P.A., Cherry Hill, NJ.
Celebrex (celecoxib) Fact Sheet
* Non-steroidal anti-inflammatory (NSAID), which inhibits only cyclooxygenase-2 (COX-2), the first in its class
* Markedly decreased risk for GI ulceration as compared to other NSAIDs
* Indicated for treatment of signs and symptoms of osteoarthritis and rheumatoid arthritis
* Available in 100 mg and 200 mg capsules
* Dosed either once or twice daily
* Side effects include abdominal pain, diarrhea and dyspepsia at low incidence
* Metabolized in liver through the cytochrome P450 2C9 system
* Contraindicated in patients with known allergy to sulfonamides and those with history of asthma, urticaria or allergic-type reactions to aspirin, other NSAIDs
* Caution with drugs that inhibit P450 2C9--may diminish effect of ACE inhibitors, furosemide and thiazides; increased rate of GI ulceration with aspirin; reduce dose with fluconazole; may increase lithium plasma levels; caution with warfarin
* Precautions with patients with pre-existing asthma, hepatic insufficiency; cannot be substituted for corticosteroids; pregnancy category C