Indobufen: an updated review of its use in the management of atherothrombosis

The efficacy and safety of indobufen in patients with ischemic cardiovascular or cerebrovascular diseases: systematic review and meta-analysis

OBJECTIVE

This meta-analysis aims to evaluate the safety and efficacy of indobufen in the treatment of cardiovascular diseases, cerebrovascular diseases, and thromboembolic disorders. The primary focus is on the incidence of major adverse cardiovascular events (MACE), thrombosis, bleeding events, and adverse reactions. The results are intended to provide a reference for the clinical application of indobufen and suggest directions for further large-scale, multi-center, prospective studies.

METHODS

This review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive search was conducted in PubMed, Embase, Web of Science, and the Cochrane Library databases to identify all relevant studies on indobufen. Twelve trials, all randomized controlled trials (RCTs), met the inclusion criteria. The results were presented as risk ratios (RR) with 95% confidence intervals (CI), and meta-analysis was performed using RevMan 5.3 and Stata 18.0 software.

RESULTS

The meta-analysis included 12 randomized controlled trials. Regarding safety, indobufen showed superior clinical outcomes compared to other antiplatelet agents regarding bleeding events, gastrointestinal adverse reactions, and overall adverse reactions, with these differences being more pronounced in cardiovascular diseases. However, the effects of both treatments on efficacy outcomes, including MACE, myocardial infarction, angina, mortality, and thrombotic events, were similar. For stroke events, particularly in patients with cerebrovascular diseases, the use of indobufen was associated with some risk.

CONCLUSION

Indobufen is associated with a lower risk of adverse reactions and bleeding, making it a viable option for patients at risk of bleeding or adverse effects, particularly in those with cardiovascular diseases. However, compared to anticoagulants such as aspirin and clopidogrel, indobufen has a shorter history of use, and its evidence base is relatively limited, highlighting the need for further research. Currently, indobufen is widely used in secondary cardiovascular and cerebrovascular prevention and provides some guidance for antiplatelet therapy in patients with gastrointestinal discomfort or bleeding risk. However, due to the potential risks in MACE, stroke, and other events, further clinical trials are needed to assess the clinical applicability of indobufen.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/, identifier (CRD42024587938).

Palladium-catalyzed regioselective carbonylation of 2-amino-2,3-diphenylpropanoate to 5/6-membered benzolactams

Five/six-membered benzolactams are significant blocks in both organic and medicinal chemistry. Achieving 5/6-membered benzolactams from the same starting compound under varying reaction conditions presents a significant challenge. Herein, palladium-catalyzed free amine-oriented regioselective C-H activations/carbonylations mediated by hexacarbonylmolybdenum, leading to diverse sizes of benzolactams, respectively, have been developed. Six-membered dihydroisoquinolinones can be obtained selectively in acetic acid using benzoquinone as an oxidant. While unfavorable five-membered isoindolinones were formed in the presence of Cu(II) as an oxidant and dihydrooxazole ligands in 1,2-dichlorobenzene. The substituents on the phenyl ring also had a great influence on the regioselectivity of the reaction. In addition, an asymmetric version of the reaction has also been attempted preliminarily.

Reversible and Non-Competitive Inhibition of Cyclooxygenase by Indobufen for Efficient Antiplatelet Action and Relief of Gastrointestinal Irritation

Clinically, indobufen is widely used for the treatment of antiplatelet aggregation and anticoagulation. Prior studies have discovered that abnormal platelet function can be promptly restored to normal when the drug is stopped. Herein, through the study of the enzyme reaction kinetics, we demonstrated that the inhibitory effect of indobufen on cyclooxygenase-1 (COX-1) was reversible and non-competitive. Specifically, the cyclooxygenase inhibition experiment showed that the level of 6-keto-PGF1α in the gastric mucosa of the indobufen-treated groups was significantly higher than that of the aspirin group (###p < 0.001), indicating a higher level of PGI2 in and a better physiological state of the gastric mucosa. Moreover, the rat gastric ulcer index and mucosal section experiments further confirmed the relief of gastrointestinal irritation and the adverse reaction rate of the indobufen-treated group compared to those of the aspirin group. Furthermore, indobufen was verified to exert reversible inhibitory activity on the heme group of COX-1 and thus reversibly inhibit COX-1 activity. In general, compared with aspirin, the long-term oral administration of indobufen yields a lower risk of gastrointestinal symptoms, such as ulcers.

Dual Antiplatelet Therapy: A Concise Review for Clinicians

Dual antiplatelet therapy (DAPT) combines two antiplatelet agents to decrease the risk of thrombotic complications associated with atherosclerotic cardiovascular diseases. Emerging data about the duration of DAPT is being published continuously. New approaches are trying to balance the time, benefits, and risks for patients taking DAPT for established cardiovascular diseases. Short-term dual DAPT of 3-6 months, or even 1 month in high-bleeding risk patients, is equivalent in terms of efficacy and effectiveness compared to long-term DAPT for patients who experienced percutaneous coronary intervention in an acute coronary syndrome setting. Prolonged DAPT beyond 12 months reduces stent thrombosis, major adverse cardiovascular events, and myocardial infarction rates but increases bleeding risk. Extended DAPT does not significantly benefit stable coronary artery disease patients in reducing stroke, myocardial infarction, or cardiovascular death. Ticagrelor and aspirin reduce cardiovascular events in stable coronary artery disease with diabetes but carry a higher bleeding risk. Antiplatelet therapy duration in atrial fibrillation patients after percutaneous coronary intervention depends on individual characteristics and bleeding risk. Antiplatelet therapy is crucial for post-coronary artery bypass graft and transcatheter aortic valve implantation; Aspirin (ASA) monotherapy is preferred. Antiplatelet therapy duration in peripheral artery disease depends on the scenario. Adding vorapaxar and cilostazol may benefit secondary prevention and claudication, respectively. Carotid artery disease patients with transient ischemic attack or stroke benefit from antiplatelet therapy and combining ASA and clopidogrel is more effective than ASA alone. The optimal duration of DAPT after carotid artery stenting is uncertain. Resistance to ASA and clopidogrel poses an incremental risk of deleterious cardiovascular events and stroke. The selection and duration of antiplatelet therapy in patients with cardiovascular disease requires careful consideration of both efficacy and safety outcomes. The use of combination therapies may provide added benefits but should be weighed against the risk of bleeding. Further research and clinical trials are needed to optimize antiplatelet treatment in different patient populations and clinical scenarios.

Indobufen versus aspirin in patients with acute ischaemic stroke in China (INSURE): a randomised, double-blind, double-dummy, active control, non-inferiority trial

BACKGROUND

Aspirin is recommended for secondary stroke prevention in patients with moderate-to-severe ischaemic stroke but can lead to gastrointestinal intolerance and bleeding. Indobufen is used as an alternative antiplatelet agent in some countries, despite an absence of large-scale clinical trials for this indication. We tested the hypothesis that indobufen is non-inferior to aspirin in reducing the risk of new stroke at 90 days in patients with moderate-to-severe ischaemic stroke.

METHODS

We conducted a randomised, double-blind, double-dummy, active control, non-inferiority trial at 163 tertiary and district general hospitals in China. Eligible participants were aged 18-80 years with acute moderate-to-severe ischaemic stroke (National Institutes of Health Stroke Scale score 4-18). We randomly assigned (1:1) participants within 72 h of the onset of symptoms to receive either indobufen (100 mg tablet twice per day) or aspirin (100 mg tablet once per day) for 90 days. The randomisation sequence was computer generated centrally and stratified by local participating centres. Masked local investigators assigned the random code to patients in ascending order and provided a treatment kit corresponding to the random code. The primary efficacy outcome was new stroke and the primary safety outcome was severe or moderate bleeding, both within 90 days. This primary efficacy outcome was assessed in all randomly assigned and consenting patients and in a per-protocol group (ie, all patients finishing the treatment without major violation of the trial protocol). Safety analyses were done in the safety-analysis population (ie, all patients who received at least one dose of the study drug and had a safety assessment available). We assessed the non-inferiority of indobufen versus aspirin using the one-sided upper limit of the 95% CI of the hazard ratio (HR) with a prespecified non-inferiority margin of 1·25. This trial is registered with ClinicalTrials.gov (NCT03871517).

FINDINGS

This trial took place between June 2, 2019, and Nov 28, 2021. Of 84 093 patients screened, 5438 patients were randomly assigned to receive either indobufen (n=2715) or aspirin (n=2723), all of whom were included in the primary analyses. Median age was 64·2 years (IQR 56·1-70·6); 1921 (35·3%) were women and 3517 (64·7%) were men. Stroke occurred within 90 days in 213 (7·9%) patients in the indobufen group versus 175 (6·4%) in the aspirin group (HR 1·23, 95% CI 1·01-1·50; pnon-inferiority=0·44). Moderate or severe bleeding occurred in 18 (0·7%) patients in the indobufen group and in 28 (1·0%) in the aspirin group (0·63, 95% CI 0·35 to 1·15; p=0·13). Adverse events within 90 days occurred in 666 (24·5%) patients in the indobufen group and 679 (24·9%) patients in the aspirin group (p=0·73).

INTERPRETATION

In patients with acute moderate-to-severe ischaemic stroke, indobufen was not non-inferior to aspirin because the upper limit of the 95% CI was greater than 1·25. Furthermore, indobufen seemed to be inferior to aspirin in reducing the risk of recurrent stroke at 90 days because the lower limit of the 95% CI was greater than 1·00. Although moderate or severe bleeding did not differ between groups, these findings do not support the use of indobufen for secondary stroke prevention in patients with moderate-to-severe ischaemic stroke.

FUNDING

Hangzhou Zhongmei Huadong Pharmaceutical and Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

The Effects of Indobufen on Micro-Inflammation and Peritoneal Transport Function in Patients Undergoing Continuous Ambulate Peritoneal Dialysis: A Prospective Randomized Controlled Study

Indobufen possesses anticoagulant and antithrombotic effects that can improve micro-inflammation and renal function. This study aimed to examine whether indobufen could improve the microinflammatory state in patients on continuous ambulatory peritoneal dialysis (CAPD) and explore its therapeutic effects on peritoneal transport function. A total of 60 patients undergoing CAPD from October 2019 to October 2020 were selected and randomized to the control and indobufen groups. All patients received conventional treatments. Blood routine and the serum and peritoneal effusion levels of tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1), cellular fibronectin (cFN), and vascular endothelial growth factor were determined before and after 6 months of treatment. The peritoneal equilibrium test (PET) was used to evaluate peritoneal transport function. There were no significant differences in PET results, microinflammatory state, and biochemical indices between the two groups before treatment (P > 0.05). After 6 months of treatment, platelet-to-lymphocyte ratio and serum and peritoneal effusion TNF-α levels in the indobufen group were decreased compared with the control group (P < 0.05). Serum and peritoneal effusion TGF-β1 and cFN levels in the indobufen group were reduced compared with the control group (P < 0.05). PET results in the indobufen group were decreased compared with baseline (P < 0.05). The difference in PET results between the two groups before and after treatment was statistically significant (P < 0.05). Indobufen could improve the peritoneal transport function in patients undergoing CAPD. The underlying mechanism might be related to the improvement of the microinflammatory state and peritoneal fibrosis. SIGNIFICANCE STATEMENT: Microinflammation and peritoneal fibrosis can lead to peritoneal failure in CAPD. Indobufen is a novel antiplatelet drug that can alleviate renal fibrosis and improve renal function in patients with diabetic nephropathy. Indobufen can improve the peritoneal transport function in patients undergoing CAPD. The mechanism of indobufen improving the peritoneal function might be related to the improvement of the microinflammatory state and peritoneal fibrosis.

Effect of indobufen vs. aspirin on platelet accumulation in patients with stable coronary heart disease after percutaneous coronary intervention: An open-label crossover study

Purpose: This study compared the effect of indobufen with that of aspirin on platelet function in patients with stable coronary heart disease after percutaneous coronary intervention (PCI).

Methods: Patients with stable coronary heart disease who had undergone PCI and received dual antiplatelet therapy (aspirin 100 mg + clopidogrel 75 mg once daily) for at least 12 months were allocated to receive indobufen 100 mg twice daily + clopidogrel 75 mg once daily, clopidogrel 75 mg once daily alone, indobufen 100 mg twice daily alone, and aspirin 100 mg once daily alone for 1 month each in an open-label crossover manner. Platelet function was assessed by using the rates of arachidonic acid (AA)-induced platelet aggregation (AA-PAR) and adenosine diphosphate (ADP)-induced platelet aggregation (ADP-PAR) measured by light transmission aggregometry, the platelet reactivity index measured by vasodilator-stimulated phosphoprotein (PRI-VASP), and the plasma and urinary thromboxane B₂ (TXB₂) concentrations recorded at baseline and during each treatment phase.

Results: Of 56 patients enrolled, 52 completed the study. The AA-PAR was lower in the indobufen alone group than in the aspirin alone group [5.21% (3.39, 7.98) vs. 5.27% (4.06, 6.60), p = 0.038], while biologically, a difference of 0.06% may represent no significant difference; there was no significant between-group difference in the plasma [531.16 pg/ml (203.89, 1035.06) vs. 373.93 pg/ml (194.04, 681.71), p = 0.251] or urinary [3951.97 pg/ml (2006.95, 6077.01) vs. 3610.48 pg/ml (1664.60, 6247.61), p = 0.717] TXB₂ concentration. When the aspirin + clopidogrel group and indobufen + clopidogrel group were compared, similar results were found for AA-PAR [3.97% (3.05, 5.12) vs. 3.83% (3.10, 5.59), p = 0.947] and both plasma [849.47 pg/ml (335.96, 1634.54) vs. 455.41 pg/ml (212.47, 1489.60), p = 0.629], and urinary [4122.97 pg/ml (2044.96, 7459.86) vs. 3812.81 pg/ml (1358.95, 6021.07), p = 0.165] TXB₂ concentrations. ADP-PAR was lower in the clopidogrel alone group than in the indobufen alone group (47.04% ± 16.89 vs. 61.7% ± 10.50, p < 0.001), as was PRI-VASP (66.53% ± 18.06 vs. 77.72% ± 19.87, p = 0.002).

Conclusion: These findings suggest that indobufen has antiplatelet effects similar to those of aspirin in patients with stable coronary heart disease after PCI, and may be an alternative for patients with aspirin intolerance after coronary stenting.

Prediction of the human in vivo antiplatelet effect of S- and R-indobufen using population pharmacodynamic modeling and simulation based on in vitro platelet aggregation test

Indobufen (Ibustrin®), a reversible inhibitor of platelet aggregation, exists in two enantiomeric forms in 1:1 ratio. Here, we characterized the anti-platelet effect of S- and R-indobufen using response surface modeling using NONMEM® and predicted the therapeutic doses exerting the maximal efficacy of each enantioselective S- and R-indobufen formulation. S- and R-indobufen were added individually or together to 24 plasma samples from drug-naïve healthy subjects, generating 892 samples containing randomly selected concentrations of the drugs of 0–128 mg/L. Collagen-induced platelet aggregation in platelet-rich plasma was determined using a Chrono-log Lumi-Aggregometer. Inhibitory sigmoid I_max model adequately described the anti-platelet effect. The S-form was more potent, whereas the R-form showed less inter-individual variation. No significant interaction was observed between the two enantiomers. The anti-platelet effect of multiple treatments with 200 mg indobufen twice daily doses was predicted in the simulation study, and the effect of S- or R-indobufen alone at various doses was predicted to define optimal dosing regimen for each enantiomer. Simulation study predicted that 200 mg twice daily administration of S-indobufen alone will produce more treatment effect than S-and R-mixture formulation. S-indobufen produced treatment effect at lower concentration than R-indobufen. However, inter-individual variation of the pharmacodynamic response was smaller in R-indobufen. The present study suggests the optimal doses of R-and S-enantioselective indobufen formulations in terms of treatment efficacy for patients with thromboembolic problems. The proposed methodology in this study can be applied to the develop novel enantio-selective drugs more efficiently.

Comparison of aspirin and indobufen in healthy volunteers

The aim of this study is to quantify the extent and recovery of platelet inhibition after administration of indobufen and aspirin in healthy volunteers. Indobufen inhibits platelet aggregation by reversibly inhibiting the platelet cyclooxygenase enzyme, thereby suppressing thromboxane synthesis. Twenty healthy volunteers completed the study and received aspirin (200 mg/day for 2 weeks) followed by a 4-week washout period and then indobufen (200 mg twice a day for 2 weeks). The percent (%) inhibition of platelet aggregation (IPA) was assessed using arachidonic acid (0.5 mg/ml) and adenosine diphosphate (5 µM) at 4, 12, 24 and 48 hours after last dose of each drug. IPA assessed using arachidonic acid as the agonist was similar at 4 hours after the last dose of indobufen (81.07 ± 9.36%) and aspirin (96.99 ± 0.29%, p = 0.10), but significantly lower at 12 hours (74.04 ± 9.55% vs. 97.94 ± 0.28%, p = 0.02), 24 hours (33.39 ± 11.13% vs. 97.48 ± 0.32%, p < 0.001) and 48 hours (14.12 ± 9.74% vs. 98.22 ± 0.31%, p < 0.001) after indobufen, compared to the relative values for aspirin. IPA assessed using adenosine diphosphate as the agonist was similar in the two groups at 4, 12 and 24 hours after the last dose, but significantly lower 48 hours after the last dose of indobufen, compared to the relative value for aspirin (1.98 ± 3.57% vs. 12.61 ± 2.71%, p = 0.002). Indobufen (200 mg twice a day) caused equivalent initial inhibition of platelet aggregation to aspirin (200 mg daily), and the anti-aggregation effect diminished faster than after aspirin.

Chronic constipation in hemiplegic patients

AIM: To assess the prevalence of bowel dysfunction in hemiplegic patients, and its relationship with the site of neurological lesion, physical immobilization and pharmacotherapy.

METHODS: Ninety consecutive hemiplegic patients and 81 consecutive orthopedic patients were investigated during physical motor rehabilitation in the same period, in the same center and on the same diet. All subjects were interviewed ≥ 3 mo after injury using a questionnaire inquiring about bowel habits before injury and at the time of the interview. Patients’ mobility was evaluated by the Adapted Patient Evaluation Conference System. Drugs considered for the analysis were nitrates, angiogenic converting enzyme (ACE) inhibitors, calcium antagonists, anticoagulants, antithrombotics, antidepressants, anti-epileptics.

RESULTS: Mobility scores were similar in the two groups. De novo constipation (OR = 5.36) was a frequent outcome of the neurological accident. Hemiplegics showed an increased risk of straining at stool (OR: 4.33), reduced call to evacuate (OR: 4.13), sensation of incomplete evacuation (OR: 3.69), use of laxatives (OR: 3.75). Logistic regression model showed that constipation was significantly and independently associated with hemiplegia. A positive association was found between constipation and use of nitrates and antithrombotics in both groups. Constipation was not related to the site of brain injury.

CONCLUSION: Chronic constipation is a possible outcome of cerebrovascular accidents occurring in 30% of neurologically stabilized hemiplegic patients. Its onset after a cerebrovascular accident appears to be independent from the injured brain hemisphere, and unrelated to physical inactivity. Pharmacological treatment with nitrates and antithrombotics may represent an independent risk factor for developing chronic constipation.

Cardiovascular Risks of Cyclooxygenase Inhibition

Millions of patients use nonsteroidal antiinflammatory drugs (NSAIDs) for relief of arthritic pain. Although NSAIDs reduce pain, their use has been linked to gastroduodenal complications. Selective inhibition of the cyclooxygenase (COX)-2 enzyme appeared to offer patients similar pain relief with an improved adverse-effect profile. However, accumulating experiences have raised concerns regarding the cardiovascular toxicities of the selective COX-2 inhibitors. Although selective COX inhibitors provide more gastrointestinal protection than NSAIDs, the unbalanced inhibition of prostaglandins may promote cardiovascular complications. Variability in study designs and inconsistency in results have made the evaluation of NSAID and COX-2 inhibitor safety very difficult, creating confusion among health care practitioners. We examine the pharmacologic and clinical evidence that defines the cardiovascular risk associated with COX inhibition.

Upper gastrointestinal bleeding associated with antiplatelet drugs

BACKGROUND

The risk of major upper gastrointestinal bleeding associated with various antiplatelet drugs and the protection conferred by gastroprotective agents are not well defined.

AIM

To estimate the risk of upper gastrointestinal bleeding associated with the use of antiplatelet drugs and its prevention by gastroprotective agents.

METHODS

In a case-control study, we compared all cases of upper gastrointestinal bleeding from a gastric or duodenal lesion in patients over 18 years of age (2813 cases), with 7193 matched controls. Odds ratios of upper gastrointestinal bleeding for individual antiplatelet drugs with adjustment for potential confounders were estimated.

RESULTS

The individual risks of upper gastrointestinal bleeding were cardiovascular acetylsalicylic acid 4.0 (3.2-4.9), clopidogrel 2.3 (0.9-6.0), dipyridamole 0.9 (0.4-2.0), indobufen 3.8 (1.2-12.2), ticlopidine 3.1 (1.8-5.1) and triflusal 1.6 (0.9-2.7). Concomitant proton pump inhibitors decreased all risk estimates. For acetylsalicylic acid plus a proton pump inhibitor, the odds ratio was 1.1 (0.5-2.6). As a group, antiplatelet drugs accounted for 14.5% of all cases of upper gastrointestinal bleeding, i.e. 58 per million per year (334 per million per year among those older than 70 years).

CONCLUSIONS

The risk of upper gastrointestinal bleeding is substantially decreased by the concomitant use of proton pump inhibitors. The risk of acetylsalicylic acid plus a proton pump inhibitor seems lower than that of ticlopidine or clopidogrel.

Do some inhibitors of COX-2 increase the risk of thromboembolic events?: Linking pharmacology with pharmacoepidemiology

Inhibitors of the cyclo-oxygenase (COX)-2 isoenzyme were developed with the expectation that their use would be accompanied by a reduction in adverse reactions thought to be mediated through COX-1 compared with conventional nonselective NSAIDs. However, the results of some clinical studies and other evidence have led to the hypothesis that use of COX-2 inhibitors may contribute to an increased risk of adverse thromboembolic (TE) events. In this review, we have evaluated the evidence from small-scale in vitro and in vivo pharmacological studies, clinical trials and large-scale pharmacoepidemiological studies and commented on the relationship between the pharmacological characteristics related to thromboembolic events and the clinical effects in large-scale clinical trials and pharmacoepidemiological studies. Overall, the pharmacological evidence suggests that a prothrombotic effect of COX-2 selective inhibitors is plausible. To date, despite the results from the Vioxx Gastrointestinal Outcome Research (VIGOR) study from which the clinical concern regarding cardiovascular TE risk arose, the published data from other randomised controlled trials (RCTs), retrospective observational studies and spontaneous reporting schemes provide a conflicting body of evidence on the TE risk with COX-2 inhibitors. Concerns that COX-2 inhibitors may be associated with prothrombotic effects remain and these need to be addressed in large scale, RCTs designed specifically to investigate the possibility of an excess of adverse cardiovascular outcomes in users of some or all selective COX-2 inhibitors, both with and without concomitant low-dose aspirin (acetylsalicylic acid). Consideration must also be given to other pathophysiological mechanisms for potential cardiovascular risk linked with inhibition of COX-2. In view of the evidence reviewed, it is recommended that selective COX-2 inhibitors should be prescribed with caution, only in patients with conditions for which these drugs have proven efficacy and with careful monitoring of outcomes and adverse events. This is particularly important in the elderly, in patients with cardiovascular/renal disease and in patients with other risk factors that might predispose them to adverse events.

Resolution of indobufen enantiomers by capillary zone electrophoresis Pharmacokinetic studies of human serum

A direct and stereospecific method was worked out to quantify indobufen enantiomers in human serum using capillary zone electrophoresis (CZE). The indobufen enantiomers and (+)-S-ketoprofen (internal standard, IS) were separated in a fused silica capillary, filled with heptakis 2,3,6-tri-O-methyl-beta-cyclodextrin as a chiral selector in a buffer of pH 5.0. Indobufen enantiomers and other non-steroidal anti-inflammatory drugs: flurbiprofen, ketoprofen and (+)-S-naproxen were also separated during one analytical run. UV absorbances of indobufen enantiomers were measured at 282 nm. Influence of temperature on resolution of the enantiomers, and the electrophoretic parameters: electrophoretic (muep) and electroosmotic (muEOF) mobilities were also determined. Validation of the method was carried out. Calibration curves of indobufen enantiomers were linear in the range of 0.2-20.0 microg/ml. Percent recovery of both enantiomers from acidified serum was calculated after extraction with methylene chloride. Intra- and inter-day measurement precision and accuracy were below 15.0%. Limits of quantitation and detection were also estimated. The elaborated method was tested in vivo after administration of a single dose of 200 mg rac-indobufen tablets to healthy volunteers. Calculated parameters confirmed usefulness of the method in human pharmacokinetic studies on indobufen enantiomers. The direct CZE method can provide an alternative to HPLC, where enantiomers used to be derivatised before determination.

Selective COX-2 inhibition and cardiovascular effects: a review of the rofecoxib development program

See related Editorials on pages 561 and 563. Cyclo-oxygenase-2 (COX-2) inhibitors appear to alter the balance of vasoactive eicosanoids (prostacyclin and thromboxane) and to suppress the inflammatory mediators implicated in the progression of atherogenesis and ischemic myocardial injury. Neutral, harmful, and beneficial cardiovascular (CV) effects have all been postulated to result from these changes. Investigations conducted with rofecoxib, a selective COX-2 inhibitor, have substantially contributed to our understanding of this scientific area. Rofecoxib had little or no effect on platelet aggregation or platelet-derived thromboxane synthesis but reduced systemic prostacyclin synthesis by 50% to 60%. These findings prompted extensive analyses of CV thrombotic events within the rofecoxib development program. Among 5435 osteoarthritis trial participants, similar rates of CV thrombotic events were reported with rofecoxib, placebo, and comparator, nonselective NSAIDs (ibuprofen, diclofenac, and nabumetone). In the VIGOR gastrointestinal outcomes trial of >8000 patients, naproxen (an NSAID with aspirin-like sustained antiplatelet effects throughout its dosing interval) was associated with a significantly lower risk of CV events than was rofecoxib. A subsequent pooled analysis from 23 studies (including VIGOR) encompassing multiple disease states and including more than 14,000 patient-years at risk also demonstrated that rofecoxib was not associated with excess CV thrombotic events compared with either placebo or nonnaproxen NSAIDs. Again, naproxen appeared to be the outlier, suggesting a cardioprotective benefit of naproxen. Finally, among the predominantly elderly, male population participating in Alzheimer trials, both rofecoxib- and placebo-treated patients had similar rates of CV thrombotic events. The totality of data is not consistent with an increased CV risk among patients taking rofecoxib.

Protein binding of indobufen enantiomers: pharmacokinetics of free fraction-studies after single or multiple doses of rac-indobufen

The binding of the enantiomers of indobufen (INDB) to human serum proteins was investigated using the racemic mixture or the pure (+)-S-enantiomer in a concentration range of 2.5-100.0 mg/L. In addition, the pharmacokinetics of free (unbound) and total INDB enantiomers were studied 1) following administration of a single 200 mg rac-INDB tablet to healthy volunteers, and 2) in obliterative atherosclerosis patients at steady state. The free fraction of INDB was obtained by ultrafiltration. Using the racemic mixture, the binding parameters of the two enantiomers were different, showing enantioselectivity in protein binding. The (-)-R-enantiomer was bound more strongly to human serum albumin, with association constant K = 11.95 +/- 0.98 x 10(5) M(-1) and n = 0.72 +/- 0.02 binding sites. The comparable data for the (+)-S-enantiomer were K = 4.65 +/- 0.02 x 10(5) M(-1), n = 0.92 +/- 0.01. When the binding of (+)-S-enantiomer was studied alone, the association constant K (2.10 +/- 0.18 x 10(5) M(-1)) was lower and the number of binding sites was increased, to n = 1.87 +/- 0.17. Competition occurred between the enantiomers, with the (-)-R-enantiomer displacing its antipode. The fraction of both enantiomers bound to serum proteins was 99.0%, which increased with decreasing initial concentration of the enantiomers. In healthy volunteers the (+)-S-enantiomer was eliminated faster than its (-)-R antipode, resulting in a lower AUC for the (+)-S-enantiomer. Significant differences were observed in the total INDB enantiomer concentrations. The mean unbound fraction of (-)-R- and (+)-S-INDB was 0.45% and 0.43%, respectively. Levels of the free (+)-S-enantiomer were higher than its (-)-R-antipode at steady state in patients with obliterative atherosclerosis who also took other drugs. The free enantiomer fraction increased to around 1% upon repeated administration. We conclude that the more rapid elimination of the (+)-S enantiomer is associated with its weaker binding to serum proteins.

Comparison of cardiovascular thrombotic events in patients with osteoarthritis treated with rofecoxib versus nonselective nonsteroidal anti-inflammatory drugs (ibuprofen, diclofenac, and nabumetone)

Aspirin, nonselective nonsteroidal anti-inflammatory drugs (NSAIDs), and specific cyclooxygenase-2 (COX-2) inhibitors each have distinctive effects on COX-1-mediated thromboxane biosynthesis, the major determinant of platelet aggregation. It is unclear whether these effects are associated with differences in thrombogenic risks. To compare the risk for thrombotic cardiovascular events among patients receiving rofecoxib, nonselective NSAIDs, and placebo, cardiovascular safety was assessed in 5,435 participants in 8 phase IIB/III osteoarthritis trials. The median treatment exposure was 31/2 months. The primary end point assessed was the risk of any arterial or venous thrombotic cardiovascular adverse event (AE). A second analysis assessed differences in the Anti-Platelet Trialists' Collaboration (APTC) events, a cluster end point that consists of the combined incidence of (1) cardiovascular, hemorrhagic, and unknown death; (2) myocardial infarction; and (3) cerebrovascular accident. Similar rates of thrombotic cardiovascular AEs were reported with rofecoxib, placebo, and comparator nonselective NSAIDs (ibuprofen, diclofenac, or nabumetone). In trials that compared rofecoxib with NSAIDs, the incidence of thrombotic cardiovascular AEs was 1.93/100 patient-years in the rofecoxib treatment group compared with 2.27/100 patient-years in the combined nonselective NSAID group. In trials that compared rofecoxib with placebo, the incidence of thrombotic cardiovascular AEs was 2.71/100 patient-years in the rofecoxib group compared with 2.57/100 patient-years in the placebo group. Consistent with the risks of cardiovascular AEs, similar rates of APTC events were reported with rofecoxib, placebo, and comparator nonselective NSAIDs. Thus, in the rofecoxib osteoarthritis development program, there was no difference between rofecoxib, comparator nonselective NSAIDs, and placebo in the risks of cardiovascular thrombotic events.

Cardiovascular thrombotic events in controlled, clinical trials of rofecoxib

BACKGROUND

In comparing aspirin, nonselective nonsteroidal antiinflammatory agents (NSAIDs), and cyclooxygenase (COX)-2 inhibitors, variation in platelet inhibitory effects exists that may be associated with differential risks of cardiovascular (CV) thrombotic events. Among the randomized, controlled trials with the COX-2 inhibitor rofecoxib, one study demonstrated a significant difference between rofecoxib and its NSAID comparator (naproxen) in the risk of CV thrombotic events. A combined analysis of individual patient data was undertaken to determine whether there was an excess of CV thrombotic events in patients treated with rofecoxib compared with those treated with placebo or nonselective NSAIDs.

METHODS AND RESULTS

CV thrombotic events were assessed across 23 phase IIb to V rofecoxib studies. Comparisons were made between patients taking rofecoxib and those taking either placebo, naproxen (an NSAID with near-complete inhibition of platelet function throughout its dosing interval), or another nonselective NSAIDs used in the development program (diclofenac, ibuprofen, and nabumetone). The major outcome measure was the combined end point used by the Antiplatelet Trialists' Collaboration, which includes CV, hemorrhagic, and unknown deaths; nonfatal myocardial infarctions; and nonfatal strokes. More than 28 000 patients, representing >14 000 patient-years at risk, were analyzed. The relative risk for an end point was 0.84 (95% CI: 0.51, 1.38) when comparing rofecoxib with placebo; 0.79 (95% CI: 0.40, 1.55) when comparing rofecoxib with non-naproxen NSAIDs; and 1.69 (95% CI: 1.07, 2.69) when comparing rofecoxib with naproxen.

CONCLUSIONS

This analysis provides no evidence for an excess of CV events for rofecoxib relative to either placebo or the non-naproxen NSAIDs that were studied. Differences observed between rofecoxib and naproxen are likely the result of the antiplatelet effects of the latter agent.