"What are COX-2 inhibitors, and how do they work?
COX-2 inhibitors are a subclass of nonsteroidal antiinflammatory drugs (NSAIDs). NSAIDs work by reducing the production of prostaglandins, chemicals that promote inflammation, pain, a"...
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Serious gastrointestinal toxicity such as bleeding, ulceration and perforation of the stomach, small intestine or large intestine can occur at any time with or without warning symptoms in patients treated with nonsteroidal anti-inflammatory drugs (NSAIDs). Minor gastrointestinal problems such as dyspepsia are common and may also occur at any time during NSAID therapy. Therefore, physicians and patients should remain alert for ulceration and bleeding even in the absence of previous GI tract symptoms. Patients should be informed about the signs and symptoms of serious GI toxicity and the steps to take if they occur. The utility of periodic laboratory monitoring has not been demonstrated, nor has it been adequately assessed. Only one in five patients who develop a serious upper GI adverse event on NSAID therapy is symptomatic. It has been demonstrated that upper GI ulcers, gross bleeding or perforation caused by NSAIDs appear to occur in approximat ely 1% of patients treated for 3 to 6 months and 2-4% of patients treated for one year. These trends continue, thus increasing the likelihood of developing a serious GI event at some time during the course of therapy. However, even short-term therapy is not without risk.
NSAIDs should be prescribed with extreme caution in patients with a prior history of ulcer disease or gastrointestinal bleeding. Most spontaneous reports of fatal GI events are in elderly or debilitated patients and therefore special care should be taken in treating this population. For high risk patients, alternate therapies that do not involve NSAIDs should be considered.
Studies have shown that patients with a prior history of peptic ulcer disease and/or gastrointestinal bleeding and who use NSAIDs, have a greater than 10-fold higher risk for developing a GI bleed than patients with neither of these risk factors. In addition to a past history of ulcer disease, pharmacoepidemiological studies have identified several other co-therapies or co-morbid conditions that may increase the risk for GI bleeding such as: treatment with oral corticosteroids, treatment with anticoagulants, longer duration of NSAID therapy, smoking, alcoholism, older age, and poor general health status. (See CLINICAL STUDIES - Safety Studies.)
Serious Skin Reactions
Serious skin reactions, including exfoliative dermatitis, Stevens-Johnson syndrome, and toxic epidermal necrolysis, have been reported through postmarketing surveillance in patients receiving BEXTRA (see ADVERSE REACTIONS-Postmarketing Experience). Fatalities due to Stevens -Johnson syndrome and toxic epidermal necrolysis have been reported. BEXTRA (valdecoxib) should be discontinued at the first appearance of skin ras h or any other sign of hypersensitivity.
In postmarketing experience, cases of hypersensitivity reactions (anaphylactic reactions and angioedema) have been reported in patients receiving BEXTRA (see ADVERSE REACTIONS Postmarketing Experience). These cases have occurred in patients with and without a history of allergictype reactions to sulfonamides (see CONTRAINDICATIONS). BEXTRA (valdecoxib) should not be given to patients with the aspirin triad. This symptom complex typically occurs in asthmatic patients who experience rhinitis with or without nasal polyps, or who exhibit severe, potentially fatal bronchospasm after taking aspirin or other NSAIDs (see CONTRAINDICATIONS and PRECAUTIONS - Pre-existing Asthma). Emergency help should be sought in cases where an anaphylactoid reaction occurs.
Advanced Renal Disease
No information is available regarding the safe use of BEXTRA (valdecoxib) Tablets in patients with advanced kidney disease. Therefore, treatment with BEXTRA (valdecoxib) is not recommended in these patients. If therapy with BEXTRA (valdecoxib) must be initiated, close monitoring of the patient's kidney function is advisable (see PRECAUTIONS - Renal Effects).
In late pregnancy, BEXTRA (valdecoxib) should be avoided because it may cause premature closure of the ductus arteriosus.
BEXTRA (valdecoxib) Tablets cannot be expected to substitute for corticosteroids or to treat corticosteroid insufficiency. Abrupt discontinuation of corticosteroids may lead to exacerbation of corticosteroid-responsive illness. Patients on prolonged corticosteroid therapy should have their therapy tapered slowly if a decision is made to discontinue corticosteroids.
The pharmacological activity of valdecoxib in reducing fever and inflammation may diminish the utility of these diagnostic signs in detecting complications of presumed noninfectious, painful conditions.
Borderline elevations of one or more liver tests may occur in up to 15% of patients taking NSAIDs. Notable elevations of ALT or AST (approximately three or more times the upper limit of normal) have been reported in approximately 1% of patients in clinical trials with NSAIDs.
These laboratory abnormalities may progress, may remain unchanged, or may remain transient with continuing therapy. Rare cases of severe hepatic reactions, including jaundice and fatal fulminant hepatitis, liver necrosis and hepatic failure (some with fatal outcome) have been reported with NSAIDs. In controlled clinical trials of valdecoxib, the incidence of borderline (defined as 1.2- to 3.0-fold) elevations of liver tests was 8.0% for valdecoxib and 8.4% for placebo, while approximately 0.3% of patients taking valdecoxib, and 0.2% of patients taking placebo, had notable (defined as greater than 3-fold) elevations of ALT or AST.
A patient with symptoms and/or signs suggesting liver dysfunction, or in whom an abnormal liver test has occurred, should be monitored carefully for evidence of the development of a more severe hepatic reaction while on therapy with BEXTRA (valdecoxib) . If clinical signs and symptoms consistent with liver disease develop, or if systemic manifestations occur (e.g., eosinophilia, rash), BEXTRA (valdecoxib) should be discontinued.
Long-term administration of NSAIDs has resulted in renal papillary necrosis and other renal injury. Renal toxicity has also been seen in patients in whom renal prostaglandins have a compensatory role in the maintenance of renal perfusion. In these patients, administration of a nonsteroidal anti-inflammatory drug may cause a dose-dependent reduction in prostaglandin formation and, secondarily, in renal blood flow, which may precipitate overt renal decompensation. Patients at greatest risk of this reaction are those with impaired renal function, heart failure, liver dysfunction, those taking diuretics and Angiotensin Converting Enzyme (ACE) inhibitors, and the elderly. Discontinuation of NSAID therapy is usually followed by recovery to the pretreatment state.
Caution should be used when initiating treatment with BEXTRA (valdecoxib) in patients with considerable dehydration. It is advisable to rehydrate patients first and then start therapy with BEXTRA (valdecoxib) . Caution is also recommended in patients with preexisting kidney disease. (See WARNINGS - Advanced Renal Disease.)
Anemia is sometimes seen in patients receiving BEXTRA (valdecoxib) . Patients on long-term treatment with BEXTRA (valdecoxib) should have their hemoglobin or hematocrit checked if they exhibit any signs or symptoms of anemia.
BEXTRA (valdecoxib) does not generally affect platelet counts, prothrombin time (PT), or activated partial thromboplastin time (APTT), and does not appear to inhibit platelet aggregation at indicated dosages (See CLINICAL STUDIES Safety Studies Platelets).
Fluid Retention and Edema
Fluid retention and edema have been observed in some patients taking BEXTRA (see ADVERSE REACTIONS). Therefore, BEXTRA (valdecoxib) should be used with caution in patients with fluid retention, hypertension, or heart failure.
Patients with asthma may have aspirin-sensitive asthma. The use of aspirin in patients with aspirin-sensitive asthma has been associated with severe bronchospasm, which can be fatal. Since cross reactivity, including bronchospasm, between aspirin and other nonsteroidal anti-inflammatory drugs has been reported in such aspirin-sensitive patients, BEXTRA (valdecoxib) should not be administered to patients with this form of aspirin sensitivity and should be used with caution in patients with preexisting asthma.
Information for Patients
BEXTRA (valdecoxib) can cause GI discomfort and, rarely, more serious GI side effects, which may result in hospitalization and even fatal outcomes. Although serious GI tract ulcerations and bleeding can occur without warning symptoms, patients should be alert for the signs and symptoms of ulcerations and bleeding, and should ask for medical advice when observing any indicative sign or symptoms. Patients should be apprised of the importance of this follow-up (see WARNINGS Gastrointestinal (GI) Effects Risk of GI Ulceration, Bleeding, and Perforation).
Patients should report to their physicians, signs or symptoms of gastrointestinal ulceration or bleeding, skin rash, weight gain, or edema.
Patients should be informed of the warning signs and symptoms of hepatotoxicity (e.g., nausea, fatigue, lethargy, pruritus, jaundice, right upper quadrant tenderness, and flu-like symptoms). If these occur, patients should be instructed to stop therapy and seek immediate medical attention.
Patients should also be instructed to seek immediate emergency help in the case of an anaphylactoid reaction (see WARNINGS Anaphylactoid Reactions).
In late pregnancy, BEXTRA (valdecoxib) should be avoided because it may cause premature closure of the ductus arteriosus.
Because serious GI tract ulcerations and bleeding can occur without warning symptoms, physicians should monitor for signs and symptoms of GI bleeding.
Valdecoxib was not carcinogenic in rats given oral doses up to 7.5 mg/kg/day for males and 1.5 mg/kg/day for females (equivalent to approximately 2- to 6-fold human exposure at 20 mg QD as measured by the AUC(0-24hr)) or in mice given oral doses up to 25 mg/kg/day for males and 50 mg/kg/day for females (equivalent to approximately 0.6- to 2.4-fold human exposure at 20 mg QD as measured by the AUC(0-24hr)) for two years.
Valdecoxib was not mutagenic in an Ames test or a mutation assay in Chinese hamster ovary (CHO) cells, nor was it clastogenic in a chromosome aberration assay in CHO cells or in an in vivo micronucleus test in rat bone marrow.
Valdecoxib did not impair male rat fertility at oral doses up to 9.0 mg/kg/day (equivalent to approximately 3- to 6-fold human exposure at 20 mg QD as measured by the AUC(0-24hr)). In female rats, a decrease in ovulation with increased pre- and post-implantation loss resulted in decreased live embryos/fetuses at doses ≥2 mg/kg/day (equivalent to approximately 2-fold human exposure at 20 mg QD as measured by the AUC(0-24hr) for valdecoxib). The effects on female fertility were reversible. This effect is expected with inhibition of prostaglandin synthesis and is not the result of irreversible alteration of female reproductive function.
Teratogenic Effects: Pregnancy Category C.
The incidence of fetuses with skeletal anomalies such as semi-bipartite thoracic vertebra centra and fused sternebrae was slightly higher in rabbits at an oral dose of 40 mg/kg/day (equivalent to approximately 72-fold human exposures at 20 mg QD as measured by the AUC(0-24hr)) throughout organogenesis. Valdecoxib was not teratogenic in rabbits up to an oral dose of 10 mg/kg/day (equivalent to approximately 8-fold human exposures at 20 mg QD as measured by the AUC(0-24hr)).
Valdecoxib was not teratogenic in rats up to an oral dose of 10 mg/kg/day (equivalent to approximately 19-fold human exposure at 20 mg QD as measured by the AUC(0-24hr)). There are no studies in pregnant women. However, valdecoxib crosses the placenta in rats and rabbits. BEXTRA (valdecoxib) should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Non-Teratogenic Effects: Valdecoxib caus ed increased pre-and post-implantation loss with reduced live fetuses at oral doses ≥10 mg/kg/day (equivalent to approximately 19-fold human exposure at 20 mg QD as measured by the AUC(0-24hr)) in rats and an oral dose of 40 mg/kg/day (equivalent to approximately 72-fold human exposure at 20 mg QD as measured by the AUC(0-24hr)) in rabbits throughout organogenesis. In addition, reduced neonatal survival and decreased neonatal body weight when rats were treated with valdecoxib at oral doses ≥6 mg/kg/day (equivalent to approximately 7-fold human exposure at 20 mg QD as measured by the AUC(0-24hr)) throughout organogenesis and lactation period.
No studies have been conducted to evaluate the effect of valdecoxib on the closure of the ductus arteriosus in humans.
Therefore, as with other drugs known to inhibit prostaglandin synthesis, use of BEXTRA (valdecoxib) during the third trimester of pregnancy should be avoided.
Labor and Delivery
Valdecoxib produced no evidence of delayed labor or parturition at oral doses up to 10 mg/kg/day in rats (equivalent to approximately 19-fold human exposure at 20 mg QD as measured by the AUC(0-24hr)).
The effects of BEXTRA (valdecoxib) on labor and delivery in pregnant women are unknown.
Valdecoxib and its active metabolite are excreted in the milk of lactating rats. It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, and because of the potential for adverse reactions in nursing infants from BEXTRA (valdecoxib) , a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother and the importance of nursing to the infant.
Safety and effectiveness of BEXTRA (valdecoxib) in pediatric patients below the age of 18 years have not been evaluated.
Of the patients who received BEXTRA (valdecoxib) in arthritis clinical trials of three months duration, or greater, approximately 2100 were 65 years of age or older, including 570 patients who were 75 years or older. No overall differences in effectiveness were observed between these patients and younger patients.This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 12/8/2004
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