Interaction of a selective cyclooxygenase-2 inhibitor with aspirin and NO-releasing aspirin in the human gastric mucosa

In addition to inhibiting cyclooxygenase (COX)-1-derived prostanoid biosynthesis, aspirin acetylates COX-2, enabling the conversion of arachidonic acid to 15(R)-epi lipoxin A4, or aspirin-triggered lipoxin (ATL). Selective COX-2 inhibitors block ATL formation and exacerbate mucosal injury in rats treated with aspirin. In the present study, we have examined whether inhibition of COX-2 activity in healthy volunteers taking aspirin exacerbates gastric mucosal injury and if such an effect would be prevented by NCX-4016, a NO-releasing derivative of aspirin. Thirty-two volunteers were randomized to receive 2 wk of treatment with NCX-4016 (800 mg twice a day) or aspirin (100 mg once a day) alone or in combination with 200 mg of celecoxib twice a day. Mucosal damage was assessed by endoscopy. The mean mucosal injury score was 5.8 +/- 1.8 in subjects treated with aspirin and 2.4 +/- 0.7 (P < 0.01 vs. aspirin) in subjects treated with NCX-4016. Administration of celecoxib increased the injury score in volunteers treated with aspirin (9.9 +/- 1.9) but not in subjects taking NCX-4016 (1.5 +/- 0.8). Aspirin and NCX-4016 caused a comparable suppression of serum thromboxane B2 levels and increased urinary excretion of ATL. Celecoxib inhibited endotoxin-induced prostaglandin E2 generation in whole blood by approximately 80% and abolished ATL formation. These findings suggests that (i) aspirin and NCX-4016 trigger ATL formation in humans, (ii) celecoxib inhibits ATL formation and exacerbates the mucosal injury caused by low doses of aspirin, and (iii) the NO-donating moiety of NCX-4016 protects the gastric mucosa even in the presence of suppression of COX-1 and COX-2.     

Co-administration of nitric oxide-aspirin (NCX-4016) and aspirin prevents platelet and monocyte activation and protects against gastric damage induced by aspirin in humans

OBJECTIVES: The goal of this study was to test the hypothesis that NCX-4016 may have broader anti-inflammatory and antithrombotic effects as well as better gastric tolerability than aspirin in humans. BACKGROUND: NCX-4016 is an aspirin derivative containing a nitric oxide-releasing moiety that prevents platelet activation and modulates tissue factor (TF) expression and cytokine release from lipopolysaccharide (LPS)-stimulated monocytes. METHODS: This was a blind-observer, placebo-controlled, parallel-group study in which 48 healthy subjects were randomized to receive NCX-4016 800 mg twice a day, NCX-4016 800 mg twice a day plus aspirin 325 mg, aspirin 325 mg, or placebo for 21 days. RESULTS: Similar to aspirin alone, NCX-4016 effectively inhibited platelet aggregation induced by 0.6 mmol/ arachidonic acid, clot-stimulated thromboxane (TX) B2 generation in whole blood, and urinary excretion of 11-dehydro-TXB2. Unlike aspirin alone, the administration of NCX-4016 significantly inhibited TF expression in monocytes stimulated ex vivo with 10 micromol/l LPS (determined by flow-cytometry analysis of TF on CD14 positive cells). NCX-4016 also inhibited the rapid TF expression induced in monocytes by a proteinase activated receptor agonist (thrombin receptor activator protein, 2 micromol/l) as well as LPS-induced expression of CD11b . Ex vivo, release of MCP-1 and interleukin-6 were significantly inhibited by NCX-4016, but not by aspirin. NCX-4016 was not associated with gastric damage, and significantly reduced gastric injury when co-administered with aspirin, although both drugs reduced gastric PGE2 production to the same extent. CONCLUSIONS: NCX-4016 is equally effective as aspirin in inhibiting cyclooxygenase activity. However, NCX-4016 causes less gastric damage and prevents monocyte activation. Larger multicenter trials are warranted to establish clinical efficacy and safety of NCX-4016.     

Effect of allopurinol, sulphasalazine, and vitamin C on aspirin induced gastroduodenal injury in human volunteers.

BACKGROUND--The mechanisms of aspirin induced gastroduodenal injury are not fully understood. Aspirin induces the release of reactive oxygen metabolites in animal models, which may contribute to mucosal injury. AIMS--To investigate the effects of aspirin administered with placebo or antioxidants on gastric mucosal reactive oxygen metabolite release and gastroduodenal injury in human volunteers. SUBJECTS--Fourteen healthy volunteers participated in the study (seven male; mean age 27 years, range 20-40). METHODS--In a double blind, randomised, crossover study, volunteers received aspirin 900 mg twice daily and either placebo, allopurinol 100 mg twice daily, sulphasalazine 1 g twice daily or vitamin C 1 g twice daily for three days. Injury was assessed endoscopically and by quantifying mucosal reactive oxygen metabolite release by measuring chemiluminescence before and after each treatment. The effect on prostanoids was determined by measuring ex vivo antral prostaglandin E2 (PGE2) synthesis and serum thromboxane B2 (TXB2). RESULTS--No drug reduced any parameter of gastric injury but vitamin C reduced duodenal injury assessed by Lanza score (p < 0.005). Chemiluminescence increased after aspirin both with placebo (p < 0.05) and vitamin C (p < 0.05). Post-treatment chemiluminescence was lower in subjects taking allopurinol (p < 0.05) or sulphasalazine (p < 0.005) than in those taking placebo with aspirin. CONCLUSIONS--In this study, aspirin induced gastric injury was associated with reactive oxygen metabolite release. This was reduced by sulphasalazine and allopurinol, although macroscopic injury was not affected. Vitamin C, however, was shown to have a previously unrecognised protective effect against aspirin induced duodenal injury.     

Pharmacodynamic interaction of naproxen with low-dose aspirin in healthy subjects

OBJECTIVES: We investigated the occurrence of pharmacodynamic interaction between low-dose aspirin and naproxen. BACKGROUND: The uncertainty of cardioprotection by naproxen has encouraged its combination with aspirin in patients with arthritis and cardiovascular disease. METHODS: The incubation of washed platelets with naproxen for 5 min before the addition of aspirin reduced the irreversible inhibition of thromboxane (TX)B(2) production by aspirin. The pharmacodynamic interaction between the two drugs was then investigated in four healthy volunteers who received aspirin (100 mg daily) for 6 days and then the combination of aspirin and naproxen for further 6 days: aspirin 2 h before naproxen (500 mg, twice-daily dosing). After 14 days of washout, naproxen was given 2 h before aspirin for further 6 days. RESULTS: The inhibition of serum TXB(2) production (index of platelet cyclooxygenase [COX]-1 activity) and platelet aggregation ex vivo and urinary 11-dehydro-TXB(2) levels (index of TXB(2) biosynthesis in vivo) by aspirin alone (99 +/- 0.2%, 95 +/- 0.6%, and 81 +/- 4%, respectively) was not significantly altered by the co-administration of naproxen, given either 2 h after aspirin or in reverse order. In a second study, the concurrent administration of a single dose of aspirin and naproxen did not affect platelet TXB(2) production and aggregation at 1 h after dosing, when aspirin alone causes maximal inhibitory effect. Moreover, the rapid recovery of platelet COX-1 activity and function supports the occurrence of a pharmacodynamic interaction between naproxen and aspirin. CONCLUSIONS: Naproxen interfered with the inhibitory effect of aspirin on platelet COX-1 activity and function. This pharmacodynamic interaction might undermine the sustained inhibition of platelet COX-1 that is necessary for aspirin's cardioprotective effects.     

Effect of ranitidine on the antiplatelet effects of aspirin in healthy human subjects

Aspirin is often taken with H2-receptor antagonists. In vitro data suggest that certain antagonists, such as ranitidine, have inhibitory effects on platelet function. There are no reports on the combined effect of aspirin and H2-receptor antagonists on platelet function in humans. Therefore, this study's aim was to evaluate the effects of aspirin, ranitidine, and their combination on platelet function in humans. Ten healthy men aged 34.7 +/- 2 years received aspirin 325 mg/day for 4 days followed by a 9-day washout period, 3 days of ranitidine treatment (150 mg twice daily), and 4 days of dual-drug treatment. Blood samples were drawn at baseline and on the last days of aspirin monotherapy, the washout period, ranitidine monotherapy, and dual-drug treatment. Platelet aggregation was measured in response to 0.5 mg/ml arachidonic acid, 5 and 10 mumol/L adenosine diphosphate, and 1 micro g/ml collagen. The Platelet Function Analyzer 100 test was performed, and blood salicylate levels were measured in 6 subjects. Aspirin caused a marked reduction in platelet aggregation and prolongation of Platelet Function Analyzer 100 closure time. Ranitidine caused a modest decrease in platelet aggregation. Unexpectedly, the combination of aspirin and ranitidine caused less inhibition of platelet aggregation and prolongation of Platelet Function Analyzer 100 time than aspirin alone (p = 0.02 to 0.07 compared with aspirin alone). Blood salicylate levels were lower when subjects took aspirin with ranitidine than when they took aspirin alone (1 +/- 0.8 vs 1.6 +/- 0.7 mg/dl, p = 0.005). In conclusion, ranitidine appears to attenuate the antiplatelet effects of aspirin in healthy volunteers. The most likely mechanism for these findings is a change in the absorption conditions of aspirin in the presence of ranitidine.     

Chronic treatment with nitric oxide-releasing aspirin reduces plasma low-density lipoprotein oxidation and oxidative stress,arterial oxidation-specific epitopes,and atherogenesis in hypercholesterolemic mice

The effects of chronic treatment with nitric oxide-containing aspirin (NO-aspirin, NCX-4016) in comparison with regular aspirin or placebo on the development of a chronic disease such as atherosclerosis were investigated in hypercholesterolemic low-density lipoprotein (LDL)-receptor-deficient mice. Male mice were assigned randomly to receive in a volume of 10 ml/kg either placebo (n = 10), 30 mg/kg/day NO-aspirin (n = 10), or 18 mg/kg/day of regular aspirin (n = 10). After 12 weeks of treatment, the computer-assisted imaging analysis revealed that NO-aspirin reduced the aortic cumulative lesion area by 39.8 +/- 12.3% compared with that of the placebo (P < 0.001). Regular aspirin did not reduce significantly aortic lesions (-5.1 +/- 2.3%) compared with the placebo [P = 0.867, not significant (NS)]. Furthermore, NO-aspirin reduced significantly plasma LDL oxidation compared with aspirin and placebo, as shown by the significant reduction of malondialdehyde content (P < 0.001) as well as by the prolongation of lag-time (P < 0.01). Similarly, systemic oxidative stress, measured by plasma isoprostanes, was significantly reduced by treatment with NCX-4016 (P < 0.05). More importantly, mice treated with NO-aspirin revealed by immunohistochemical analysis of aortic serial sections a significant decrease in the intimal presence of oxidation-specific epitopes of oxLDL (E06 monoclonal antibody, P < 0.01), and macrophages-derived foam cells (F4/80 monoclonal antibody, P < 0.05), compared with placebo or aspirin. These data indicate that enhanced NO release by chronic treatment with the NO-containing aspirin has antiatherosclerotic and antioxidant effects in the arterial wall of hypercholesterolemic mice.     

Ranitidine protects against gastroduodenal mucosal damage associated with chronic aspirin therapy

A randomized, double-blind, placebo-controlled study examined whether concomitant administration of ranitidine could protect against the gastroduodenal mucosal damage associated with long-term aspirin therapy in healthy men. Twenty-four subjects received ranitidine (150 mg twice daily) plus aspirin (650 mg four times daily), and 19 received placebo twice daily plus aspirin (650 mg four times daily) for four weeks. Gastric injury and duodenal injury were assessed separately according to a numerical rating scale for incidence and severity of lesions observed during endoscopic examinations at baseline and after four weeks of treatment. The ranitidine/aspirin group had significantly less mucosal damage in the stomach and duodenum than the placebo/aspirin group. Mean serum salicylate levels were similar between treatment groups after two and four weeks of aspirin therapy. Therefore, the protective effect of ranitidine was achieved with no compromise in salicylate absorption.     

Overestimation of platelet aspirin resistance detection by thrombelastograph platelet mapping and validation by conventional aggregometry using arachidonic acid stimulation.

OBJECTIVES: This study sought to determine the prevalence of platelet aspirin resistance using methods that directly indicate the degree of platelet cyclooxygenase inhibition. BACKGROUND: Aspirin resistance in platelets may be overestimated by nonspecific laboratory measurements that do not isolate cyclooxygenase activity. METHODS: Arachidonic acid (AA)-induced light-transmittance platelet aggregation (LTA) and thrombelastography (TEG) platelet mapping were performed on the blood of healthy subjects (n = 6) before and 24 h after receiving 325 mg aspirin, and on 223 patients reporting compliance with long-term daily aspirin treatment (n = 203 undergoing percutaneous intervention [PCI] and n = 20 with a history of stent thrombosis). Aspirin resistance was defined as >20% aggregation by LTA or >50% aggregation by TEG. RESULTS: In healthy subjects, AA-induced aggregation by LTA was 82 +/- 10% before and 2 +/- 1% at 24 h after aspirin (p < 0.001), and aggregation by TEG was 86 +/- 14% before and 5 +/- 7% at 24 h after aspirin (p < 0.001). In compliant patients, AA-induced aggregation by LTA was 3 +/- 2% before PCI and 3 +/- 2% after PCI (p = NS), and aggregation by TEG was 5 +/- 9% before PCI and 6 +/- 14% after PCI (p = NS). Seven PCI patients were noncompliant, and all were aspirin sensitive after in-hospital aspirin treatment. Among 223 patients, only one patient ( approximately 0.4%) was resistant to aspirin treatment. CONCLUSIONS: Platelet aspirin resistance assessed by methods that directly indicate inhibition of cyclooxygenase is rare in compliant patients with coronary artery disease.     

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?p?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.     

Reversal to cisplatin sensitivity in recurrent human ovarian cancer cells by NCX-4016, a nitro derivative of aspirin

Ovarian cancer is a gynecological malignancy that is commonly treated by cytoreductive surgery followed by cisplatin treatment. However, the cisplatin treatment, although successful initially, is not effective in the treatment of the recurrent disease that invariably surfaces within a few months of the initial treatment. The refractory behavior is attributed to the increased levels of cellular thiols apparently caused by the cisplatin treatment. This observation prompted us to choose a cytotoxic drug whose activity is potentiated by cellular thiols with enhanced specificity toward the thiol-rich cisplatin-resistant cells. We used NCX-4016 [2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester], a derivative of aspirin containing a nitro group that releases nitric oxide in a sustained fashion for several hours in cells and in vivo, and we studied its cytotoxic efficacy against human ovarian cancer cells (HOCCs). Cisplatin-sensitive and cisplatin-resistant (CR) HOCCs were treated with 100 microM NCX-4016 for 6 h, and/or 0.5 microg/ml cisplatin for 1 h and assayed for clonogenecity. NCX-4016 significantly reduced the surviving fractions of cisplatin-sensitive (63 +/- 6%) and CR (70 +/- 10%) HOCCs. NCX-4016 also caused a 50% reduction in the levels of cellular glutathione in CR HOCCs. Treatment of cells with NCX-4016 followed by cisplatin showed a significantly greater extent of toxicity when compared with treatment of cells with NCX-4016 or cisplatin alone. In conclusion, this study showed that NCX-4016 is a potential inhibitor of the proliferation of CR HOCCs and thus might specifically kill cisplatin-refractory cancer cells in patients with recurrent ovarian cancer.     

No effect of taurine on platelet aggregation in men with a predisposition to type 2 diabetes mellitus

Any diet therapy that potentially could affect platelet function would also influence the initiation of atherosclerotic plaque formation which is an important complication of diabetes mellitus eventually resulting in myocardial infarction and stroke. Blood platelets are rich in taurine, and it has been shown that taurine inhibits platelet aggregation in healthy subjects. The purpose was to examine the effect of taurine supplementation on platelet aggregation in high-risk subjects with a positive family history of T2DM. Twenty healthy men were included in a double-blinded, randomized, crossover study, receiving daily supplementation of 1.5 g taurine or placebo for two 8-week periods. Subjects were overweight and first-degree relatives of T2DM patients. At the end of each treatment, fasting blood samples for assessment of platelet aggregation was drawn. Platelet aggregation was induced by ADP. Plasma taurine concentration was significantly greater after taurine intervention compared to placebo (131.4+/-61.7 vs. 38.9+/-6.7 micromol/l, P<0.0001). There was no difference in the threshold level for complete platelet aggregation induced by ADP in vivo between placebo and taurine intervention (placebo 3.86+/-2.21 vs. taurine 3.86+/-3.25 micromol/l). Supplementation with 1.5 g of taurine for 8 weeks had no effect on platelet aggregation in overweight prediabetic men.     

Effect of sucralfate on aspirin induced mucosal injury and impaired haemostasis in humans.

BACKGROUND: Sucralfate does not have potent anti-ulcerogenic actions in users of non-steroidal anti-inflammatory drugs (NSAIDs). However, sucralfate may influence intragastric haemostasis favourably. AIM: To investigate separately the effects of sucralfate on acute gastric and duodenal injury and on changes in intragastric bleeding induced by aspirin. METHOD: On three occasions, 24 healthy volunteers received three days' treatment with aspirin 900 mg twice daily together with placebo, sucralfate 2 g twice daily or sucralfate 1 g four times daily. Injury was assessed endoscopically and bleeding by spontaneous and biopsy induced bleeding intragastric washings. Ex vivo prostaglandin E2 (PGE2) synthesis and serum thromboxane were measured by using radioimmunoassay. RESULTS: Aspirin significantly inhibited ex vivo gastric mucosal PGE2 synthesis, reduced serum thromboxane, caused gastric erosions, and increased spontaneous and biopsy induced bleeding. Sucralfate had no significant effects on endoscopic injury but sucralfate 1 g four times daily significantly reduced spontaneous and biopsy induced bleeding. Similar trends were seen with sucralfate 2 g twice daily but the results were less consistent. CONCLUSION: Sucralfate does not affect aspirin induced acute gastric mucosal injury but reduces aspirin associated intragastric bleeding.     

Effect of dipyridamole alone and in combination with aspirin on whole blood platelet aggregation, PGI2 generation, and red cell deformability ex vivo in man

STUDY OBJECTIVE--The aim was to investigate the effects of dipyridamole, aspirin, and a combination of dipyridamole plus aspirin on platelet aggregation in whole blood, PGI2 generation, and red cell deformability ex vivo. SUBJECTS--were 16 male volunteers, aged 22-39 years, mean age, 26.6 years. DESIGN--This was a randomised, double blind, placebo controlled trial. The volunteer received each of the following treatments 10 days apart: dipyridamole 200 mg; aspirin 300 mg; dipyridamole 200 mg plus aspirin 300 mg; matched placebos. MEASUREMENTS AND MAIN RESULTS--Blood was taken for platelet function tests, PGI2 metabolite assay, and red cell deformability before and 2 h after the trial dose was taken. Platelet aggregation was quantified by measuring the fall in single platelet count after stimulation with 2 micrograms.ml-1 collagen or 50 nM platelet activating factor (PAF), or by rollermixing aliquots of blood to initiate spontaneous aggregation. The platelet function tests were completed at 37 degrees C within 10 min of venepuncture. The stable metabolite of PGI2, 6-keto PGF1 alpha, was measured in serum. There was inhibition of spontaneous platelet aggregation by dipyridamole (p less than 0.004), aspirin (p less than 0.005), and the combination of dipyridamole plus aspirin (p less than 0.0001) as compared with placebo. PAF induced platelet aggregation was inhibited by dipyridamole (p less than 0.002) and the combination of dipyridamole plus aspirin (p less than 0.0001) but aspirin alone had no inhibitory effect. Collagen induced platelet aggregation was inhibited by all three treatments: dipyridamole (p less than 0.06), aspirin (p less than 0.0001), and the combination of dipyridamole plus aspirin (p less than 0.0001). PGI2 generation was markedly inhibited by aspirin (p less than 0.0001) and the combination doses (p less than 0.0001) but was unaffected by dipyridamole alone. Of the three active treatments, only dipyridamole alone significantly (p less than 0.001) increased red cell deformability; there was a modest decrease in red cell deformability with aspirin. CONCLUSIONS--The results with PAF support the view that dipyridamole inhibits platelet activation by more than one mechanism; the effect on collagen induced and spontaneous platelet aggregation suggests that the effect of the combination doses is additive and that on red cell deformability the synergy is negative.     

Platelet inhibitory activity and pharmacokinetics of prasugrel (CS-747) a novel thienopyridine P2Y12 inhibitor: a multiple-dose study in healthy humans

This double-blind, placebo-controlled trial evaluated the safety, pharmacodynamics, and pharmacokinetics of prasugrel (CS-747, LY640315), a novel thienopyridine P2Y12 ADP receptor antagonist, during multiple oral dosing in healthy subjects. Eighteen subjects received placebo, or prasugrel 2.5 or 10 mg, orally, daily for 10 days. Adverse events were recorded and blood samples for measurement of platelet aggregation, bleeding time, and prasugrel metabolite concentrations were obtained. Two bleeding events were experienced in the prasugrel 10 mg dose group and one in the placebo group. Neither of the events was considered serious. ADP-induced platelet aggregation accumulated over the 10-day study period, reaching a steady state by days 2-4 following administration of prasugrel 10 mg daily. Limited inhibition of platelet aggregation was obtained with prasugrel 2.5 mg. In the 10-mg dose group at day 5, 4 h postdose, with 20 microM ADP as the agonist, inhibition of platelet aggregation was 61.2 +/- 5.6 vs. 17.9 +/- 6.2% in the placebo group (P < 0.01). Recovery of platelet aggregation was observed 48 h after the last dose of prasugrel 10 mg, but was only partial, consistent with irreversible platelet inhibition. The mean bleeding time was prolonged by day 5 at 4 h postdose in all subjects in the prasugrel 10 mg dose group (prasugrel 10 mg, 1058 +/- 412 s vs. placebo, 196 +/- 74 s; P < 0.001). The maximum plasma concentration of metabolites increased with prasugrel dose and there was no accumulation of metabolites over the 10-day study period. This study indicated that prasugrel 10 mg daily for 10 days was well tolerated and at steady-state provided sustained high levels of inhibition of platelet aggregation.     

Cumulative inhibitory effect of low-dose aspirin on vascular prostacyclin and platelet thromboxane production in patients with atherosclerosis

The relationship between the antithrombotic and antiplatelet effects of aspirin is complex, since aspirin influences other systems that protect against thrombosis as well as inhibiting platelet function. We investigated possible cumulative effects of low-dose aspirin on vascular production of prostacyclin in patients with documented atherosclerotic cardiovascular disease. Candidates for coronary artery vein graft bypass ingested 20 mg of aspirin daily during the week before surgery, and platelet aggregation, platelet formation of thromboxane A2 (TXA2), aortic and saphenous vein production of prostacyclin (PGI2), and hemostatic status were measured at the time of the bypass surgery. Low-dose aspirin markedly inhibited platelet aggregation responses and reduced TXA2 generation by greater than 90%, effects similar to those observed with much higher doses of aspirin. Both aortic and saphenous vein production of PGI2 were inhibited by 50% compared with PGI2 produced by vascular tissues of control subjects who received no aspirin preoperatively (51 +/- 10 pg 6-keto-PGF1 alpha/mg aortic wet weight [mean +/- SEM] in aspirin-treated subjects vs 130 +/- 16 pg/mg in control subjects, and 71 +/- 8 pg/mg saphenous vein wet weight vs 131 +/- 17 pg/mg). Blood loss at surgery was not significantly increased by preoperative low-dose aspirin as measured by chest tube drainage (754 +/- 229 ml in aspirin-treated subjects vs 645 +/- 271 ml in control subjects), hematocrit nadir (31.2 +/- 1.9% vs 31.8 +/- 1.7%), or transfusions (2.2 +/- 1.3 units of red blood cells vs 2.2 +/- 1.7 units).(ABSTRACT TRUNCATED AT 250 WORDS)     

Rofecoxib, a COX-2 inhibitor, does not inhibit human gastric mucosal prostaglandin production

BACKGROUND & AIMS: Rofecoxib, an inhibitor of the inducible cyclooxygenase (COX)-2 enzyme, appears not to cause acute gastroduodenal injury or chronic ulceration. To attribute this to COX-2 selectivity with sparing of gastric mucosal prostaglandin synthesis requires direct proof. METHODS: Twenty-four healthy, nonsmoking Helicobacter pylori-negative volunteers were randomized to 1 of 2 separate concurrent blinded crossover studies. Sixteen volunteers received rofecoxib, 50 mg once daily, for 5 days in one treatment period and placebo in the other. Eight volunteers similarly received naproxen, 500 mg twice daily, and placebo. On day 5 of each period, antral mucosal prostaglandin E2 (PGE2) synthesis was measured by radioimmunoassay after vortexing for 3 minutes. Whole blood COX-1 activity was measured as serum thromboxane (TXB)2- and COX-2 activity as lipopolysaccharide (LPS)-induced PGE2. RESULTS: Naproxen decreased gastric mucosal PGE2 synthesis by 65% (90% confidence interval [CI], 53%-74%; P = 0.001 vs. placebo) in contrast to an 18% increase after rofecoxib (90% CI, -11% to 57%; P = 0.313 vs. placebo). Naproxen also significantly inhibited both serum TXB2 by 94% and LPS-induced PGE2 production by 77% (both P < or = 0.002 vs. placebo), but rofecoxib only inhibited COX-2-dependent LPS-induced PGE(2) (by 79%; P < 0.001 vs. placebo). CONCLUSIONS: Rofecoxib (50 mg) lacked naproxen's ability to reduce the availability of gastroprotective prostaglandins.     

Healing with basic fibroblast growth factor is associated with reduced indomethacin induced relapse in a human model of gastric ulceration.

BACKGROUND: Acid stable basic fibroblast growth factor (bFGF) promotes angiogenesis and healing of gastric ulcers in rats and reduces subsequent non-steroidal anti-inflammatory drug (NSAID) induced relapse. AIMS: To test in a double blind, placebo controlled, three way crossover study whether bFGF promotes healing and reduces subsequent relapse in a human model of gastric ulceration. SUBJECTS: Twelve healthy volunteers. METHODS: Subjects took aspirin 900 mg twice daily (days 1-3) with bFGF 0.1 mg twice daily or cimetidine 400 mg twice daily or placebo (days 1-14) and then indomethacin 50 mg thrice daily (days 15-21). Endoscopy was performed on days 1, 4, 8, 15, and 22 during each treatment period. Eight antral biopsy specimens were taken on day 1 and the number of unhealed biopsy induced mini-ulcers and NSAID induced erosions counted during subsequent endoscopies. RESULTS: Basic FGF and cimetidine were protective against aspirin and indomethacin induced duodenal (but not gastric) injury compared with placebo. There was significant relapse of biopsy induced mini-ulcers after indomethacin only in the placebo group (0 (0-0) before v 1 (0-4.5) after; p > 0.05). TGP-580 was detected in serum of one volunteer. CONCLUSIONS: Healing with bFGF (and cimetidine) was associated with reduced NSAID induced ulcer relapse in this model of gastric ulceration.     

Effects of aspirin and NO-aspirin (NCX 4016) on platelet function and coagulation in human endotoxemia

Acetylsalicylic acid (ASA) prevents thromboembolic events by inhibiting platelet function through blocking of cyclooxygenase type 1 (COX-1). A nitroderivate of ASA, 2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)-phenyl ester (NCX 4016) was synthesized, which additionally acts through nitric oxide release. In various in vitro and animal studies NCX 4016 exhibited antithrombotic and anti-platelet properties. We used the standardized model of endotoxin infusion into human volunteers to compare the effects of NCX 4016 and ASA on platelet function and TF-induced coagulation activation. The trial consisted of two parts. In the first part, 10 healthy male volunteers were included in a randomized, open cross-over trial to find a NCX formulation with optimal tolerability and pharmacokinetic data were obtained. The second part was a randomized, double blind placebo controlled clinical trial consisting of 30 healthy male volunteers in three parallel groups (n = 10 per group). Volunteers received either NCX 4016 (800 mg b.i.d.), ASA (425 mg b.i.d.) or placebo for 7 days, before infusion of 2 ng/kg endotoxin on day 8. ASA attenuated the endotoxin-induced platelet plug formation (measured by PFA-100) significantly better than NCX 4016 and placebo (p < 0.004), while there was no difference in soluble P-selectin or VWF-levels. Urine 11-dehydro-thromboxane B₂ levels were significantly lower in the ASA and NCX 4016 groups as compared to placebo (p < 0.05). Neither ASA nor NCX 4016 significantly changed prothrombin fragment_{1 + 2}, D-Dimer or tissue factor (TF)-mRNA levels. In summary, NCX 4016 had no effect on VWF release, platelet activation as measured by soluble P-selectin or TF gene expression. NCX 4016, at the dose tested, unlike ASA, had no effect on platelet collagen/epinephrine induced plug formation under high shear rates.     

Cumulative antiplatelet effect of low-dose enteric coated aspirin

Enteric coated aspirin (ECA) at doses of 325-1300 mg is an effective alternative to regular aspirin for inhibition of platelet activity while avoiding gastric irritation. The objectives of this study were to determine: (1) the lowest chronic dose of ECA providing effective inhibition of platelet activities, (2) the time course of the inhibition, and (3) the reappearance of platelet cyclo-oxygenase activity. Seven subjects were studied before and after seven daily doses of 40-325 mg ECA. Serum thromboxane (TX) B2 levels indicated that the lowest dose of ECA resulting in greater than 90% inhibition of platelet cyclo-oxygenase was 80 mg/d. Platelet aggregation and ATP release in response to collagen (1 microgram/ml) and arachidonic acid (1 mM) were abolished and bleeding times were prolonged from 6.1 +/- 1.5 min to 9.7 +/- 2.8 min (mean +/- SD, P less than 0.01). Examination of platelet cyclo-oxygenase activity on a daily basis revealed that 24 h after the first 80 mg dose serum TXB2 had decreased by approximately 60% and was suppressed by more than 90% after four doses. Recovery of platelet cyclo-oxygenase activity after a single 80 mg dose of ECA was delayed for 48-72 h indicating that aspirin reached the systemic circulation. We conclude that chronic inhibition of platelet activity may be achieved in a cumulative manner with 80 mg ECA/d.     

Efficacy and age-related effects of nitric oxide-releasing aspirin on experimental restenosis

Restenosis after percutaneous transluminal coronary angioplasty is caused by neointimal hyperplasia, which involves impairment of nitric oxide (NO)-dependent pathways, and may be further exacerbated by a concomitant aging process. We compared the effects of NO-releasing-aspirin (NCX-4016) and aspirin (ASA) on experimental restenosis in both adult and elderly rats. Moreover, to ascertain the efficacy of NCX-4016 during vascular aging, we fully characterized the release of bioactive NO by the drug. Sprague-Dawley rats aged 6 and 24 months were treated with NO releasing-aspirin (55 mg/kg) or ASA (30 mg/kg) for 7 days before and 21 days after standard carotid balloon injury. Histological examination and immunohistochemical double-staining were used to evaluate restenosis. Plasma nitrite and nitrate and S-nitrosothiols were determined by a chemiluminescence-based assay. Electron spin resonance was used for determining nitrosylhemoglobin. Treatment of aged rats with NCX-4016 was associated with increased bioactive NO, compared with ASA. NO aspirin, but not ASA, reduced experimental restenosis in old rats, an effect associated with reduced vascular smooth muscle cell proliferation. NCX-4016, but not ASA, was well tolerated and virtually devoid of gastric damage in either adult or old rats. Thus, impairment of NO-dependent mechanisms may be involved in the development of restenosis in old rats. We suggest that an NCX-4016 derivative could be an effective drug in reducing restenosis, especially in the presence of aging and/or gastrointestinal damage.