Gastropathy due to celecoxib, a cyclooxygenase-2 inhibitor

Physiologically based pharmacokinetic (PBPK) modeling for prediction of celecoxib pharmacokinetics according to CYP2C9 genetic polymorphism

Celecoxib is a non-steroidal anti-inflammatory drug (NSAID) and a representative selective cyclooxygenase (COX)-2 inhibitor, which is commonly prescribed for osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, acute pain, and primary dysmenorrhea. It is mainly metabolized by CYP2C9 and partly by CYP3A4 after oral administration. Many studies reported that CYP2C9 genetic polymorphism has significant effects on the pharmacokinetics of celecoxib and the occurrence of adverse drug reactions. The aim of this study was to develop a physiologically based pharmacokinetic (PBPK) model of celecoxib according to CYP2C9 genetic polymorphism for personalized pharmacotherapy. Initially, a clinical pharmacokinetic study was conducted where a single dose (200 mg) of celecoxib was administered to 39 healthy Korean subjects with CYP2C9*1/*1 or CYP2C9*1/*3 genotypes to obtain data for PBPK development. Based on the conducted pharmacokinetic study and a previous pharmacokinetic study involving subjects with CYP2C9*1/*13 and CYP2C9*3/*3 genotype, PBPK model for celecoxib was developed. A PBPK model for CYP2C9*1/*1 genotype group was developed and then scaled to other genotype groups (CYP2C9*1/*3, CYP2C9*1/*13 and CYP2C9*3/*3). After model development, model validation was performed with comparison of five pharmacokinetic studies. As a result, the developed PBPK model of celecoxib successfully described the pharmacokinetics of each CYP2C9 genotype group and its predicted values were within the acceptance criterion. Additionally, all the predicted values were within two-fold error range in comparison to the previous pharmacokinetic studies. This study demonstrates the possibility of determining the appropriate dosage of celecoxib for each individual through the PBPK modeling with CYP2C9 genomic information. This approach could contribute to the reduction of adverse drug reactions of celecoxib and enable precision medicine.

Effects of CYP2C9 genetic polymorphisms on the pharmacokinetics of celecoxib and its carboxylic acid metabolite

Celecoxib, a selective cyclooxygenase (COX)-2 inhibitor, is used for the treatment of rheumatoid arthritis and osteoarthritis. The predominant hepatic metabolism of celecoxib to celecoxib carboxylic acid (CCA) is mediated mainly by CYP2C9. We investigated the effects of the major CYP2C9 genetic variants in Asian populations, CYP2C9*3 and CYP2C9*13, on the pharmacokinetics of celecoxib and its carboxylic acid metabolite in healthy Korean subjects. A single 200-mg oral dose of celecoxib was given to 52 Korean subjects with different CYP2C9 genotypes: CYP2C9EM (n = 26; CYP2C9*1/*1), CYP2C9IM (n = 24; CYP2C9*1/*3 and *1/*13), and CYP2C9PM (n = 2; CYP2C9*3/*3). Celecoxib and CCA concentrations in plasma samples collected up to 48 or 96 h after drug intake were determined by HPLC-MS/MS. The mean area under the plasma concentration-time curve (AUC_0-∞) of celecoxib was increased 1.63-fold (P < 0.001), and the apparent oral clearance (CL/F) of celecoxib was decreased by 39.6% in the CYP2C9IM genotype group compared with that of CYP2C9EM (P < 0.001). The overall pharmacokinetic parameters for celecoxib in CYP2C9*1/*13 subjects were similar to those in CYP2C9*1/*3 subjects. Two subjects with CYP2C9PM genotype both showed markedly higher AUC_0-∞, prolonged half-life, and lower CL/F for celecoxib than did subjects with CYP2C9EM and IM genotypes. CYP2C9*3 and CYP2C9*13 variant alleles significantly affected the plasma concentration of celecoxib.

Review of the selective COX-2 inhibitors celecoxib and rofecoxib: focus on clinical aspects

The selective cyclooxygenase-2 (COX-2) inhibitors celecoxib and rofecoxib were designed to have similar efficacy but less gastrointestinal toxicity than traditional nonsteroidal anti-inflammatory drugs (NSAIDs). Their efficacy has been demonstrated in the treatment of osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, postoperative dental pain and dysmenorrhea. These agents produce fewer endoscopic ulcers, symptomatic ulcers and gastrointestinal bleeds than traditional NSAIDs; although the absolute benefit is small and the gastropreserving effect is negated by concurrent use of low-dose aspirin for cardiovascular risk reduction. Nephrotoxicity and hyptertension remain concerns with COX-2 inhibitors, as they are with traditional NSAIDs. COX-2 inhibitors may be safe alternatives to traditional NSAIDs for patients with aspirin-sensitive asthma.

Pathological effects of drugs on the gastrointestinal tract: a review

Drug-induced injury of the gastrointestinal (GI) tract is increasingly common but generally under-recognized. Although there is an overwhelming number of drugs that are associated with adverse GI effects, there is a limited number of characteristic injury patterns that should prompt consideration of drug-induced GI pathology. These include the following: erosions, ulcers, and strictures; crystal deposition; parietal cell changes; reactive gastropathy; pseudodysplastic changes; microscopic colitis; infectious or necrotizing enterocolitis; ischemic colitis; focal active colitis; and increased epithelial apoptosis. This article reviews morphological and pathophysiological features of some of the more common and pathologically recognizable drug-related injury patterns and provides a practical guide for the recognition and diagnosis of drug-induced pathology in the upper and lower GI tract.

Interleukin-8, cyclo-oxygenase-2, and trefoil factor family 1 gene expression and their association with Helicobacter pylori infection in the remnant stomach

PURPOSE

The risk factors for secondary stomach carcinogenesis after distal gastrectomy have not been evaluated in detail.

METHODS

Using gastrointestinal endoscopy, we examined 112 patients who had undergone gastrectomy. Biopsy specimens were taken from the stoma and the upper corpus mucosa in the remnant stomach to examine the associations among Helicobacter pylori (H.pylori) infection, bile reflux, and the expressions of interleukin-8 (IL-8), cyclo-oxygenase-2 (COX-2), and trefoil factor family 1 (TFF1) genes in the stomach mucosa.

RESULTS

The IL-8 levels in the corpus mucosa were significantly higher in the H.pylori-positive patients than in the H.pylori-negative patients (P = 0.015). The IL-8 levels were significantly higher in the stomal mucosa than in the corpus mucosa in the H.pylori-positive patients (P = 0.047). The COX-2 levels in the corpus mucosa tended to be higher in the H.pylori-positive patients, but these levels were not significantly different in the stoma mucosa. The COX-2 levels in the corpus were significantly higher after Billroth II (BII) anastomosis than after Billroth I (BI) anastomosis (P = 0.041). TFF1 expression in the stoma was higher in the H.pylori-positive patients than in the H.pylori-negative patients, but the difference was not significant.

CONCLUSIONS

Both H.pylori infection and bile reflux increased IL-8 levels after BI anastomosis. Furthermore, COX-2 levels were higher after BII than after BI anastomosis. These indicators will become useful not only as biomarkers to predict the degree of inflammation in the stomach mucosa, but also as surrogate biomarkers to predict the risk of secondary stomach carcinogenesis in the remnant stomach mucosa.

Opioid-sparing effects of diclofenac and paracetamol lead to improved outcomes after cardiac surgery

OBJECTIVE

This study assessed the analgesic efficacy, side effects, time to extubation, and oxygenation of 3 analgesic regimens after coronary artery bypass surgery using diclofenac, paracetamol, and placebo suppositories.

DESIGN

Prospective, randomized, double-blind, placebo-controlled study.

SETTING

Referral center for cardiothoracic surgery at a university hospital.

PARTICIPANTS

Sixty consenting adults scheduled for elective coronary artery bypass grafting (CABG).

INTERVENTIONS

Patients were divided into 3 groups postoperatively: diclofenac/paracetamol: diclofenac, 100 mg rectally, and paracetamol, 1 g rectally. Diclofenac was repeated after 18 hours and paracetamol every 6 hours for 24 hours; diclofenac: diclofenac as in diclofenac/paracetamol, with placebos replacing paracetamol; and placebo: 2 placebo suppositories at same times as diclofenac/paracetamol. All patients received morphine patient-controlled analgesia.

RESULTS

Twenty-four hour morphine consumption with diclofenac/paracetamol was 12 +/- 6 mg, diclofenac 22 +/- 13 mg, and placebo 37 +/- 15 mg (diclofenac/paracetamol and diclofenac, p = 0.0003 and p = 0.0159 compared with placebo). Patients in the placebo group had significantly greater pain scores at 12 and 24 hours compared with diclofenac/paracetamol and diclofenac. Extubation time was significantly prolonged in the placebo group compared with the diclofenac/paracetamol and diclofenac groups (mean [SD] minutes diclofenac/paracetamol, diclofenac, and placebo 478 [150], 487 [257], and 710 [326], respectively). Oxygenation following extubation was significantly lower in the placebo group compared with the diclofenac/paracetamol and diclofenac groups (mean [SD] mmHg: diclofenac/paracetamol, diclofenac, and placebo 175 [44], 157 [43], and 117 [22], respectively). Episodes of nausea and vomiting were significantly less in the diclofenac/paracetamol and diclofenac groups than in the placebo group (46% and 51% reduction, respectively). all groups had similar blood loss and change in serum creatinine.

CONCLUSION

Diclofenac alone or with paracetamol has a significant opioid-sparing effect after CABG, producing more rapid extubation and better oxygenation.

Safety profile of celecoxib as used in general practice in England: results of a prescription-event monitoring study

AIMS

A post-marketing surveillance study using the technique of Prescription Event Monitoring was undertaken to monitor the safety of celecoxib, a cyclo-oxygenase (COX)-2 inhibitor, as prescribed in primary care in England.

METHODS

Patients were identified from dispensed British National Health Service prescription data supplied in confidence by the Prescription Pricing Authority for celecoxib between May and December 2000. Simple questionnaires were sent to the prescribing general practitioner at least 6 months after the date of the first dispensed prescription for each individual patient. Event incidence densities (IDs) [the number of 1st reports per 1000 patient-months of exposure (pme)] were calculated. ID differences for events reported in month 1 (ID1) and months 2-6 (ID2) were examined for temporal changes in event rate. Information on suspected adverse drug reactions (ADRs), reasons for stopping treatment, outcome of pregnancies and cause of death were also requested. Data were gathered on potential gastrointestinal (GI) risk factors [recent use of other non-steroidal anti-inflammatory drugs (NSAIDs), past history of upper GI disorders and concomitant gastro-irritant agents or anti-ulcer drugs]. Crude IDs per 1000 pme and ID ratios were calculated according to potential risk factors, and age (> or = 65 years, < or = 64 years).

RESULTS

The cohort comprised of 17,458 patients [median age 62 years (IQR 51,73); 68.3% female]. The most common specified indication was osteoarthritis (28.1%, n = 4905). Not effective was the event with the highest ID1 (139.9 per 1000 pme). The clinical events with the highest ID1 were dyspepsia (25.4 per 1000 pme) followed by abdominal pain (10.6). These were also given frequently as reasons for stopping (551 and 174 of 9126 reports). Of 436 events in 325 patients (1.9% of total cohort) that were reported as ADRs, the most frequent were events within the alimentary system (186 reports). Uncommon events reported during treatment (not necessarily as ADRs) included allergy (0.10%, n = 17), anaphylaxis (0.01%, n = 2), angioneurotic oedema (0.02%, n = 3) and bronchospasm (0.05%, n = 9). There were 103 reports of events associated with thromboembolism and 111 reports of serious GI events [90 GI bleeds (upper and lower); 21 peptic ulcers] received during treatment or within 1 month of stopping. A past history of dyspeptic/other upper GI conditions and use of concomitant gastro-protective drugs were each associated with a significantly increased risk of dyspepsia and abdominal pain.

CONCLUSIONS

Frequently reported adverse events were those GI events commonly associated with treatment with other NSAIDS. Stratification by identified risk factors suggested that channelling of high-risk patients is likely. Serious upper and lower GI events, and thromboembolic events did occur during this study, although the incidence was low (< 1%). Doctors should continue to prescribe NSAIDs, including COX-2-specific inhibitors, with caution.

Cyclooxygenase-2 and prostaglandins in articular tissues

OBJECTIVES

To provide an overview on: 1) the expression of cyclooxygenase (COX)-2 in articular tissues; 2) the role of prostaglandin E2 (PGE2) in these tissue functions; and 3) clinical trials with COX-2-selective nonsteroidal anti-inflammatory drugs (NSAIDs) (coxibs).

METHODS

MEDLINE search was performed using the key words "cyclooxygenase," "prostaglandin," "osteoarthritis" (OA), and "rheumatoid arthritis" (RA). Selected publications related to clinical trials with coxibs also are included.

RESULTS

COX-2 is upregulated in inflamed joint tissues and is responsible for elevated PGE2 production. The overexpression of COX-2 is likely induced by proinflammatory mediators such as interleukin-1beta (IL-1beta) and tumor necrosis factor (TNF) alpha. However, the exact molecular mechanisms through which the expression of COX-2 is regulated remain to be elucidated. Several studies suggest that PGE2 is involved in inflammation, apoptosis, angiogenesis, and possibly structural changes that characterize arthritic diseases. NSAIDs are prescribed for the treatment of OA and RA and provide effective relief from symptoms; however, serious gastrointestinal complications occur with their use. The clinical efficacy of NSAIDs is primarily related to the inhibition of COX-2, whereas much of the toxicity is related to COX-1 inhibition. Selective COX-2 inhibitors (coxibs) that spare COX-1 at therapeutic doses are more effective than placebo and as effective as other NSAIDs for relief of symptoms of OA and RA, and have significantly improved gastrointestinal safety and tolerability. However, some studies showed that COX-2-selective inhibitors still have classic NSAID complications.

CONCLUSIONS

Overexpression of COX-2 protein in articular tissues is a characteristic feature of arthritic diseases. However, the molecular mechanisms involved in the regulation of COX-2 expression and activity are still unclear. Elucidating the mechanisms of COX-2 expression and PGE2 production and action will help identify novel and more selective potential drug targets in the treatment of arthritic diseases.

Influence of CYP2C9 genetic polymorphisms on pharmacokinetics of celecoxib and its metabolites

In-vitro data indicate major effects of the genetically polymorphic cytochrome P450 enzyme 2C9 (CYP2C9) on the pharmacokinetics of celecoxib, a nonsteroidal anti-inflammatory drug acting as selective cyclooxygenase-2 inhibitor. Human studies report decreased clearance in heterozygous carriers of the CYP2C9 variant Ile359Leu (*3), but results appeared controversial and only data on single subjects carrying the homozygous CYP2C9*3/*3 genotype have been published. We measured single-dose kinetics of celecoxib and its main metabolites hydroxy- and carboxy-celecoxib in 21 healthy volunteers who were selected as hetero- (n = 4) and homozygous (n = 3) carriers of CYP2C9 variants Arg144Cys (*2) and Ile359Leu (*3). Blood concentrations of celecoxib and its metabolites hydroxy-celecoxib and carboxy-celecoxib were quantified by high-performance liquid chromatography. A more than two-fold reduced oral clearance in homozygous carriers of CYP2C9*3 was seen for celecoxib compared to carriers of the wild-type genotype CYP2C9*1/*1 and heterozygous carriers of one *3 allele were in-between (P = 0.003 for trend), whereas CYP2C9*2 had no significant influence on celecoxib pharmacokinetics. Decreased concentrations of carboxy- and hydroxy-celecoxib in heterozygous and homozygous carriers of CYP2C9*3 were detected which supported the influence of CYP2C9 polymorphisms on celecoxib pharmacokinetic variability. Approximately 0.5% of Caucasians carrying the genotype CYP2C9*3/*3 will have greatly increased internal exposure to celecoxib. It remains to be shown whether this is associated with greater efficacy or with an increased incidence and severity of adverse events.

Phospholipase A(2) isoforms: a perspective

Several new PLA(2)s have been identified based on their nucleotide gene sequences. They were classified mainly into three groups: cytosolic PLA(2) (cPLA(2)), secretary PLA(2) (sPLA(2)), and intracellular PLA(2) (iPLA(2)). They differ from each other in terms of substrate specificity, Ca(2+) requirement and lipid modification. The questions that still remain to be addressed are the subcellular localization and differential regulation of the isoforms in various cell types and under different physiological conditions. It is required to identify the downstream events that occur upon PLA(2) activation, particularly target protein or metabolic pathway for liberated arachidonic acid or other fatty acids. Understanding the same will greatly help in the development of potent and specific pharmacological modulators that can be used for basic research and clinical applications. The information of the human and other genomes of PLA(2)s, combined with the use of proteomics and genetically manipulated mouse models of different diseases, will illuminate us about the specific and potentially overlapping roles of individual phospholipases as mediators of physiological and pathological processes. Hopefully, such understanding will enable the development of specific agents aimed at decreasing the potential contribution of individual secretary phospholipases to vascular diseases. The signaling cascades involved in the activation of cPLA(2) by mitogen activated protein kinases (MAPKs) is now evident. It has been demonstrated that p44 MAPK phosphorylates cPLA(2) and increases its activity in cells and tissues. The phosphorylation of cPLA(2) at ser505 occurs before the increase in intracellular Ca(2+) that facilitate the binding of the lipid binding domain of cPLA(2) to phospholipids, promoting its translocation to cellular membranes and AA release. Recently, a negative feed back loop for cPLA(2) activation by MAPK has been proposed. If PLA(2) activation in a given model depends on PKC, PKA, cAMP, or MAPK then inhibition of these phosphorylating enzymes may alter activities of PLA(2) isoforms during cellular injury. Understanding the signaling pathways involved in the activation/deactivation of PLA(2) during cellular injury will point to key events that can be used to prevent the cellular injury. Furthermore, to date, there is limited information available regarding the regulation of iPLA(2) or sPLA(2) by these pathways.

Cox-2 inhibitors: today and tomorrow

The elucidation of inducible cyclooxygenase (Cox-2) dependent inflammatory pathways led to the development of specific Cox-2 inhibitors, the coxibs. These agents include the currently available celecoxib and rofecoxib and such second-generation agents as parecoxib, valdecoxib, and etoricoxib. The therapeutic advantage of coxibs is founded primarily in their lack of significant gastrointestinal (GI) side effects. Clinical trials have demonstrated the efficacy of coxibs to be completely comparable with traditional nonsteroidal anti-inflammatory drugs (NSAIDs), and pharmacoeconomics suggest favorable cost/benefit ratios with these agents compared with traditional NSAIDs, related to their reduced GI complication profiles and lower indirect costs associated with disability. Although several clinical questions remain (eg, use with low-dose aspirin, risk of thrombosis, myocardial infarction, edema, and hypertension), the emergence and clinical utility of coxibs is likely to continue on the basis of their efficacy and relative GI safety advantage. Although newer, more specific Cox-2 inhibitors may alter the choice, it is likely that this class of anti-inflammatories will become (if they have not already) the drugs of first choice in the treatment of acute pain, chronic pain, and most rheumatic conditions in the 21st century. In addition to the treatment of rheumatic conditions, it is possible that coxibs will also be of clinical utility in protection against malignant transformation and Alzheimer disease.

Gastrointestinal bleeds associated with rofecoxib

Data suggest that cyclooxygenase (COX)-2 inhibitors are safer for the gastrointestinal tract than traditional nonsteroidal antiinflammatory drugs (NSAIDs). Rofecoxib, a COX-2-specific NSAID, does not inhibit the COX-1 enzyme, thereby decreasing the potential for gastrointestinal-related adverse effects. Patients who are at an increased risk for NSAID-related gastrointestinal bleeding are therefore appropriate candidates for COX-2 inhibitors. Although the agents provide benefits for many patients, gastrointestinal-related side effects may occur, and caution should be practiced when prescribing COX-2 inhibitors. We report two patients who were admitted to the hospital with diagnoses of gastrointestinal bleeds while they were taking rofecoxib.

Meeting the therapeutic challenge of the patient with osteoarthritis

OBJECTIVE

To discuss the diagnosis of osteoarthritis and the efficacy of available pharmacologic and nonpharmacologic treatment options.

DATA SOURCES

Published reports on the diagnosis and treatment of osteoarthritis were identified through a MEDLINE search of English-language journal articles using a focused title search for the keywords acetaminophen, nonsteroidal anti-inflammatory, COX-2 nonsteroidal, opioids, capsaicin, tramadol, glucosamine, hyaluronic acid, and osteoarthritis and by reviewing the bibliographies of selected reviews. The American College of Rheumatology (ACR) guidelines, as updated in September 2000, for the treatment of osteoarthritis of the hip and knee were analyzed with appropriate references to clinical and scientific studies, review articles, and other published guidelines.

DATA SYNTHESIS

Each patient's medical history and level of pain should decide the most appropriate treatment. Nonpharmacologic therapies should always be included in the treatment regimen. If further pain management is required, the most appropriate pharmacologic treatments are acetaminophen or nonsteroidal anti-inflammatory drugs for mild-to-moderate pain, tramadol or opioid combinations for moderate-to-moderately severe pain, and opioids for severe pain. Adjunctive treatments, intraarticular injections, and surgery are also viable options for some patients.

CONCLUSION

If used properly, the ACR guidelines for the treatment of osteoarthritis are important tools in the care of the patient with this disease.

In-vitro metabolism of celecoxib, a cyclooxygenase-2 inhibitor, by allelic variant forms of human liver microsomal cytochrome P450 2C9: correlation with CYP2C9 genotype and in-vivo pharmacokinetics

In-vitro studies were conducted to assess the impact of CYP2C9 genotype on the metabolism (methyl hydroxylation) and pharmacokinetics of celecoxib, a novel cyclooxygenase-2 inhibitor and CYP2C9 substrate. When compared to cDNA-expressed wild-type CYP2C9 (CYP2C9*1), the Vmax/Km ratio for celecoxib methyl hydroxylation was reduced by 34% and 90% in the presence of recombinant CYP2C9*2 and CYP2C9*3, respectively. These data indicated that the amino acid substitution at position 359 (Ile to Leu) elicited a more pronounced effect on the metabolism of celecoxib than did a substitution at position 144 (Arg to Cys). The Vmax/Km ratio was also decreased in microsomes of livers genotyped CYP2C9*1/*2 (47% decrease, mean of two livers), or CYP2C9*1/*3 (59% decrease, one liver). In all cases, these changes were largely reflective of a decrease in Vmax, with a minimal change in Km. Based on simulations of the in-vitro data obtained with the recombinant CYP2C9 proteins, it was anticipated that the pharmacokinetics of celecoxib (as a much as a five-fold increase in plasma AUC) would be altered (versus CYP2C9*1/*1 subjects) in subjects genotyped heterozygous or homozygous for the CYP2C9*2 (Cys144) or CYP2C9*3 (Leu359) allele. In a subsequent clinical study, the AUC of celecoxib was increased (versus CYP2C9*1/*1 subjects) approximately 2.2-fold (range, 1.6-3-fold) in two CYP2C9*1/*3 subjects and one CYP2C9*3/*3 subject receiving a single oral dose (200 mg) of the drug. In contrast, there was no significant change in celecoxib AUC in two subjects genotyped CYP2C9*1/*2.

The ever-emerging anti-inflammatories. Have there been any real advances?

Gastrointestinal (GI) Adverse Drug Reactions (ADRs) from the NSAIDs are a major cause of morbidity and mortality in arthritic patients taking these drugs. The recent much heralded development of COX-2 selective drugs (celecoxib, rofecoxib), the objective of which has been to spare inhibition of the production of COX-1 derived mucosal protective prostaglandins, may have represented an advance in reducing the risk of serious ADRs--ulcers and bleeding--but does not appear to have reduced the incidence of symptomatic side-effects (nausea, vomiting, epigastric pain/heartburn, abdominal discomfort) which are a major reason for withdrawal from NSAID therapy, especially in the long term. The rationale of COX-2 selectivity from these newer drugs is controversial since there may be pharmacokinetic differences from established carboxylate-NSAIDs that accounts for their apparent lower ulcerogenicity. Moreover, concerns have been recently expressed that as COX-2 is important in ulcer healing, control of prostacyclin production and renal function that they may have adverse reactions from these effects. Indeed, recent reports of enhanced risk of congestive heart failure with rofecoxib are of importance and may relate to impaired prostacyclin production. Moreover, there are other therapeutic strategies that have yielded equally low ulcerogenic NSAIDs (e.g. the prodrug, nabumetone; the established COX-2 inhibitory drug, nimesulide) and even the well-established NSAIDs ibuprofen and diclofenac have relatively low upper GI ulcerogenicity and have been used as benchmark standards in comparative trials of the newer "Oxib" drugs (celecoxib, rofecoxib). Much research interest has centred on the nitric oxide-donating NSAIDs (NO-NSAIDs). The rationale for donating NSAIDs being to counteract the vasoconstriction effects of NSAIDs but this has yet to be fully evaluated. It is not certain that this "antidote" approach will be acceptable as there may also be systemic effects of the nitrobutoxyl--or other NO-donors that may have toxicological consequences. Another strategy is the development of mixed COX-5 lipoxygenase (LOX) inhibitors--the progenitors of which were benoxaprofen and BW-755C. The rationale of reducing the potential for lipoxygenase mediated actions in the stomach (e.g. vasoconstriction, leucocyte accumulation). Clearly, the need to develop newer NSAIDs with lower risks of ulcers and bleeding as well as symptomatic ADRs is still representing a major challenge.

Celecoxib: a new option in the treatment of arthropathies and familial adenomatous polyposis

The discovery of the two isoenzymes of cyclooxygenase (COX) has recently lead to the development and clinical introduction of specific inhibitors of cyclooxygenase-2 (COX-2), such as celecoxib, onto the market. Celecoxib is an effective anti-inflammatory, analgesic and antipyretic agent therapeutically utilised in the management of osteoarthritis and rheumatoid arthritis. In addition, celecoxib has some novel therapeutic and pharmacological activities. Celecoxib inhibits anti-apoptotic kinase activation and is the first specific COX-2 inhibitor to be marketed for familial adenomatous polyposis, an inheritable predisposition for colorectal cancer. Celecoxib is not without gastrointestinal (GI) side effects but demonstrates markedly reduced GI ulceration in clinical trials when compared to traditional non-specific non-steroidal anti-inflammatory drugs (NSAIDs). The specific COX-2 inhibitors each have distinctive pharmacokinetic properties. Celecoxib can be given either once or twice daily. Racial differences in drug disposition, and pharmacokinetic changes in elderly patients, patients with chronic renal insufficiency and patients with mild to moderate hepatic impairment, are evident with celecoxib. Despite the specific action of these drugs, there remains the potential for significant drug interactions. Celecoxib has demonstrated interactions with fluconazole, lithium and warfarin. Increased clinical vigilance should be maintained when co-prescribing medications with celecoxib until further clinical experience is gained. Celecoxib represents a major therapeutic advance in terms of GI safety. However, long-term safety in other organ systems, safety with concomitant drug administration, and pharmacoeconomic benefits still remain to be proven.

Inhibition of phospholipase A(2) as a therapeutic target

The hydrolysis of cell membrane phospholipids by phospholipase A(2) (PLA(2)) leads to the production of numerous lipid mediators of diverse pathological conditions, mainly inflammatory diseases. These include lysophospholipids and their derivatives, and arachidonic acid and its derivatives (the eicosanoids). Both these groups of mediators are produced predominantly by the secretory PLA(2)s (sPLA(2)s) which hydrolyze the phospholipids of the cell surface membrane. Protection of cell membrane from these 'inflammatory enzymes' can therefore be used for the treatment of inflammatory processes. A prototype of cell-impermeable PLA(2) inhibitors, which protect the cell membrane from different sPLA(2)s without affecting vital phospholipid metabolism, is presented and discussed in the present review.

The "aspirin" of the new millennium: cyclooxygenase-2 inhibitors

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit prostaglandin synthesis via the cyclooxygenase (COX) enzyme, the key to both therapeutic benefits and toxicity. COX enzyme exists in 2 isoforms, COX-1 and COX-2. COX-1 enzyme is thought to mediate "housekeeping" or homeostatic functions, and COX-2 is considered an inducible enzyme in response to injury or inflammation. COX-2 inhibitors are the "next-generation" NSAIDs that may selectively block the COX-2 isoenzyme without affecting COX-1 function. This may result in control of pain and inflammation with a lower rate of adverse effects compared with older nonselective NSAIDs. Rapidly evolving evidence suggests that COX-2 enzyme has a diverse physiologic and pathologic role. This article addresses the role of COX-2 enzyme in health and disease as well as the potential therapeutic value and safety issues related to COX-2 inhibition.

The gastroduodenal toxicity of nonsteroidal anti-inflammatory drugs: a review of the literature

Nonsteroidal anti-inflammatory drugs (NSAIDs) are popular and important for the treatment of inflammation and pain. However, conventional NSAIDs are intrinsically toxic to the gastroduodenal (GD) mucosa. The literature can, and should, guide us towards safer prescribing of NSAIDs. Factors known to increase the risk of GD toxicity include: history of peptic ulcer disease; advanced age; high doses; and coadministration of aspirin, anticoagulants or corticosteroids. Patients with any one of these risk factors, with the possible exception of age alone, should receive gastroprotective prophylaxis with proton pump inhibitors or misoprostol. Standard dose H2 antagonists do not protect against NSAID-induced gastric ulcers and are unsuitable for prophylaxis. Awareness of risk factors and appropriate prophylactic agents will minimize the risk to patients. Whether the new generation of highly selective COX-2 inhibitors and nitric oxide-donating NSAIDs are safer drugs in long-term use be remains to be proven, though initial clinical trial data are positive.

Clinical pharmacokinetics and pharmacodynamics of celecoxib: a selective cyclo-oxygenase-2 inhibitor

Celecoxib, a nonsteroidal anti-inflammatory drug (NSAID), is the first specific inhibitor of cyclo-oxygenase-2 (COX-2) approved to treat patients with rheumatism and osteoarthritis. Preliminary data suggest that celecoxib also has analgesic and anticancer properties. The selective inhibition of COX-2 is thought to lead to a reduction in the unwanted effects of NSAIDs. Upper gastrointestinal complication rates in clinical trials are significantly lower for celecoxib than for traditional nonselective NSAIDs (e.g. naproxen, ibuprofen and diclofenac). The rate of absorption of celexocib is moderate when given orally (peak plasma drug concentration occurs after 2 to 4 hours), although the extent of absorption is not known. Celexocib is extensively protein bound, primarily to plasma albumin, and has an apparent volume of distribution of 455+/-166L in humans. The area under the plasma concentration-time curve (AUC) of celecoxib increases in proportion to increasing oral doses between 100 and 800mg. Celecoxib is eliminated following biotransformation to carboxylic acid and glucuronide metabolites that are excreted in urine and faeces, with little drug (2%) being eliminated unchanged in the urine. Celecoxib is metabolised primarily by the cytochrome P450 (CYP) 2C9 isoenzyme and has an elimination half-life of about 11 hours in healthy individuals. Racial differences in drug disposition and pharmacokinetic changes in the elderly have been reported for celecoxib. Plasma concentrations (AUC) of celecoxib appear to be 43% lower in patients with chronic renal insufficiency [glomerular filtration rate 2.1 to 3.6 L/h (35 to 60 ml/min)] compared with individuals with healthy renal function, with a 47% increase in apparent clearance. Compared with healthy controls, it has been reported that the steady-state AUC is increased by approximately 40% and 180% in patients with mild and moderate hepatic impairment, respectively. Celecoxib does not appear to interact with warfarin, ketoconazole or methotrexate; however, clinically significant drug interactions with fluconazole and lithium have been documented. As celecoxib is metabolised by CYP2C9, increased clinical vigilance is required during the coadministration of other substrates or inhibitors of this enzyme.

Potentiation of oral anticoagulation and hemarthrosis associated with nabumetone

Concomitant therapy with warfarin and nonsteroidal antiinflammatory drugs (NSAIDs) is of concern due to the potential for increased bleeding. Nonsteroidal antiinflammatory drugs may alter patient response to warfarin by pharmacodynamic or pharmacokinetic interactions. A man receiving long-term, stable warfarin therapy experienced a significant increase in international normalized ratio 1 week after nabumetone was added to his regimen. Despite prompt reduction of the warfarin dosage, he experienced hemarthrosis of his right knee. Previous reports suggested lack of interaction between nabumetone and warfarin. Caution and close monitoring are advisable when the two agents are administered concomitantly.

Evaluation of Novel New NSAIDs: A Review of COX-2 Inhibitors, with an Emphasis on Gastrointestinal Toxicity

Identification of two isoforms of cyclooxygenase, COX-1 and COX-2, has initiated a revolution in the approach to pharmacologie pain management. It has been further determined that inhibition of COX-2 reduces inflammation, and inhibition of COX-1 compromises gastrointestinal mucosal integrity. As traditional nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit both COX-1 and COX-2, gastrointestinal ulceration can develop in association with the use of these agents to control pain and inflammation. An ideal NSAID would, therefore, inhibit COX-2 to provide anti-inflammatory effects while leaving COX-1, and, therefore, gastrointestinal mucosa, unaffected.

Two selective COX-2 inhibitors have recently been approved in the United States. Celecoxib (Celebrex, G.D. Searle & Co.) and rofecoxib (Vioxxj, Merck & Co., Inc.) are indicated for the treatment of osteoarthritis. Also, celecoxib is approved for rheumatoid arthritis. Rofecoxib is also approved for the treatment of acute pain and dysmenorrhea. Both agents have displayed similar efficacy to traditional NSAIDs. In addition, endoscopically detected gastrointestinal ulceration is reduced versus older NSAIDs. Further evaluation of selective COX-2 inhibitors will elucidate long-term efficacy, safety, and potential reduction of health care dollars spent on hospitalization and treatment for NSAID-induced gastrointestinal toxicity.