Effect of ibuprofen on cardioprotective effect of aspirin

Treatment with ibuprofen might limit the cardioprotective effects of aspirin. We aimed to assess whether patients with known cardiovascular disease who take low-dose aspirin and ibuprofen have increased risk of cardiovascular mortality. We studied 7107 patients who were discharged after first admission for cardiovascular disease between April, 1989, and April, 1997, and who were prescribed low-dose aspirin (<325 mg/day) and survived for at least 1 month. Compared with those who used aspirin alone, patients taking aspirin plus ibuprofen had an increased risk of all-cause mortality (adjusted hazard ratio 1.93, 95% CI 1.30-2.87, p=0.0011) and cardiovascular mortality (1.73, 1.05-2.84, p=0.0305). Our finding lends support to the hypothesis that ibuprofen may interact with the cardioprotective effects of aspirin, at least in patients with established cardiovascular disease.

On the interaction of specific prostaglandin H synthase-2 inhibitors with prostaglandin H synthase-1

Previous studies with both intact cells and ram seminal vesicles microsomes have shown that the specific PGHS-2 inhibitors NS-398 (N-[2-(cyclohexyloxy)-4-nitrophenyl]methanesulfonamide) and DuP-697 (5-bromo-2[4-fluorophenyl]-3-[4-methylsulfonylphenyl]-thiophene) attenuate the inhibition of PGHS-1 caused by aspirin and indomethacin. This effect occurs at concentrations of PGHS-2 inhibitors that do not inhibit the cyclooxygenase activity of PGHS-1. Here we study the effect of NS-398 and ibuprofen, a nonspecific inhibitor, on the indomethacin-induced inhibition of purified PGHS-1 and compare this effect with that observed with microsomal enzyme. Dissociation constants are obtained for the interaction of NS-398 with the purified and microsomal PGHS-1 using curve fitting of experimental data on the interaction of indomethacin with the enzyme. The dissociation constants for ibuprofen and NS-398 for interaction with PGHS-1 are similar. This finding indicates that specific PGHS-2 inhibitors are similar to ibuprofen in their ability to compete with aspirin, an irreversible time-dependent inhibitor of PGHS-1 often used for prevention of spontaneous thrombosis. Importantly, the concentrations at which PGHS-2 inhibitors attenuate the inhibition induced by aspirin and indomethacin are well below those required to cause inhibition of PGHS-1. Our results suggest that arachidonic acid not only competes with PGHS-2 inhibitors for binding to the cyclooxygenase site of PGHS-1 but it also reduces the affinities of PGHS-1 for these inhibitors by an additional, as yet unresolved mechanism.

Effects of desmopressin on thrombogenesis in aspirin-induced platelet dysfunction

Aspirin causes a coagulation disorder. Desmopressin has haemostatic effects by increasing the plasma levels of coagulation factor VIII and von Willebrand factor. The precise effects of desmopressin on thrombogenesis are not known. In an in vivo model, we investigated the effect of the drug on thrombus formation and platelet function after aspirin use. Male Lewis rats weighing 250-300 g were used. Four groups with 10 animals each were formed: control, aspirin, desmopressin and aspirin + desmopressin. In each animal, the femoral artery was dissected. A thrombogenic vessel injury was created by inverting a full thickness portion of the proximal edge of the incised artery into the lumen. The following parameters were measured: maximum thrombus size, time period until maximum thrombus size was reached and overall platelet function. In addition, the thrombi generated were investigated histologically. Thrombus formation time was significantly shorter with desmopressin compared with the animals treated with aspirin (P < 0.0001) and controls (P = 0.008). Maximum thrombus size was larger in the desmopressin and desmopressin + aspirin groups when compared with the group treated with aspirin only. Overall platelet function was significantly enhanced with desmopressin compared with controls (P = 0.025) and with aspirin (P < 0.0001). The differences were confirmed histologically. In conclusion, desmopressin significantly accelerates thrombus formation in aspirin-treated animals. It can also re-establish thrombus size after the use of aspirin. Overall platelet function is significantly increased by desmopressin.

Cyclooxygenase inhibitors and the antiplatelet effects of aspirin

BACKGROUND

Patients with arthritis and vascular disease may receive both low-dose aspirin and other nonsteroidal antiinflammatory drugs. We therefore investigated potential interactions between aspirin and commonly prescribed arthritis therapies

METHODS

We administered the following combinations of drugs for six days: aspirin (81 mg every morning) two hours before ibuprofen (400 mg every morning) and the same medications in the reverse order; aspirin two hours before acetaminophen (1000 mg every morning) and the same medications in the reverse order; aspirin two hours before the cyclooxygenase-2 inhibitor rofecoxib (25 mg every morning) and the same medications in the reverse order; enteric-coated aspirin two hours before ibuprofen (400 mg three times a day); and enteric-coated aspirin two hours before delayed-release diclofenac (75 mg twice daily)

RESULTS

Serum thromboxane B(2) levels (an index of cyclooxygenase-1 activity in platelets) and platelet aggregation were maximally inhibited 24 hours after the administration of aspirin on day 6 in the subjects who took aspirin before a single daily dose of any other drug, as well as in those who took rofecoxib or acetaminophen before taking aspirin. In contrast, inhibition of serum thromboxane B(2) formation and platelet aggregation by aspirin was blocked when a single daily dose of ibuprofen was given before aspirin, as well as when multiple daily doses of ibuprofen were given. The concomitant administration of rofecoxib, acetaminophen, or diclofenac did not affect the pharmacodynamics of aspirin

CONCLUSIONS

The concomitant administration of ibuprofen but not rofecoxib, acetaminophen, or diclofenac antagonizes the irreversible platelet inhibition induced by aspirin. Treatment with ibuprofen in patients with increased cardiovascular risk may limit the cardioprotective effects of aspirin.

Monitoring a clinical trial conducted under the Food and Drug Administration regulations allowing a waiver of prospective informed consent: the diaspirin cross-linked hemoglobin traumatic hemorrhagic shock efficacy trial

In 1996, the US Food and Drug Administration (FDA) enacted Rule 21 CFR section 50.24, which allows a narrow exception to the requirement for prospective informed consent from human research subjects in clinical trials investigating potentially beneficial therapies for acute, life-threatening conditions. The first clinical trial to be conducted under this rule was sponsored by Baxter Healthcare Corporation and approved by the FDA on November 21, 1996. This large, multicenter, randomized clinical trial was designed to compare the addition of diaspirin cross-linked hemoglobin (DCLHb) with standard care in the initial resuscitation of adults experiencing severe, uncompensated, traumatic hemorrhagic shock. Before the first planned interim analysis of the data, review of fatal adverse events revealed an imbalance in mortality between the 2 treatment groups. The Data Monitoring Committee (DMC) recommended suspension of patient enrollment 24 days later. Additional data collection and analyses confirmed the excess number of deaths in patients treated with DCLHb but failed to reveal the cause of these deaths. The trial was formally terminated after only 112 of the planned 850 patients had been enrolled. We review the events leading up to and the rationale behind the DMC recommendations for suspension of patient enrollment and trial termination. Although the DCLHb trial was unsuccessful in achieving its goals, the monitoring process worked well. Emergency research was facilitated by DMC oversight, and the interests of research subjects were protected by the actions of the DMC.

The effect of vasodilators on aspirin-induced antagonism of t-PA thrombolysis

Although i.v. t-PA has proven successful in reducing neurologic deficits in acute ischemic stroke, the disadvantages of a narrow therapeutic time window and the failure of thrombolysis in more than 50% of patients treated have necessitated an examination of adjuvant therapies to improve the rate of thrombolysis. Experimentally, the combination of aspirin therapy with t-PA has resulted in a paradoxical antagonism of thrombolysis. Reversal of this antagonism with nitric oxide (NO) donors suggested that aspirin may inhibit/ antagonize NO-related mechanisms. Using this rabbit model of thromboembolic stroke, this hypothesis is now expanded to compare two clinically relevant anti-hypertensive agents, atenolol (NO-dependent) and hydralazine (NO-independent), for their ability to improve t-PA-mediated clot lysis following aspirin pre-treatment. Thirty rabbits (10 per group) were pre-treated with aspirin (20mg kg(-1), i.v.) and then randomized to receive either vehicle, atenolol (20 microg kg(-1) h(-1), i.v.) or hydralazine (10 microg kg(-1) min(-1), i.v.) beginning 30 min following autologous clot embolization. All rabbits then received t-PA (6.3 mg kg(-1), i.v.) beginning 1 h after embolization, with completion of the protocol 4 h after embolization. Aspirin therapy reduced regional cerebral blood flow (rCBF) from 82.8m +/- 4.7 to 62.5 +/- 6.6 (n = 30; p = 0.0005). In the aspirin control group only 30% (3 of 10) rabbits demonstrated complete clot lysis, whereas the combined atenolol (60%) and hydralazine (70%) groups experienced a clot lysis rate of 65% (13 of 20 rabbits), similar to clot lysis rates previously observed with t-PA alone. In a separate series of experiments, all agents able to reverse aspirin antagonism of thrombolysis demonstrated an improvement in rCBF, suggesting a common mechanism for this diverse group of agents in reversing aspirin's antagonism of thrombolysis.

Pharmacological activity of Abies pindrow

The widely known tree Abies pindrow (Talisapatra) (family: Pinaceae), famous for its diverse clinical uses in Ayurvedic medicines, was investigated to rationalise some of the ancient claims. The petroleum ether (PE), benzene (BE), chloroform (CE), acetone (AE) and ethanol (EE) extracts of A. pindrow leaf were found to have mast cell stabilizing action in rats. The EE, AE and BE extracts offered bronchoprotection against histamine challenge in guinea-pigs. The BE, CE and PE extracts had protective role in aspirin-induced ulcer in rats. The results suggest that while terpenoids, flavonoids, glycosides and steroids are involved in mast cell protection, terpenoids and flavonoids are brochoprotective against histamine-induced bronchospasm. The ulcer protective action of PE, BE and CE fractions of A. pindrow may be attributable to steroids contents only because though all the extracts tested positive for glycosides, the extracts EE and AE did not have any ulcer protective role.

Evaluation of the effects of aspirin combined with angiotensin-converting enzyme inhibitors in patients with coronary artery disease

BACKGROUND

Several studies have suggested that there may be an interaction between angiotensin-converting enzyme (ACE) inhibitors and aspirin in patients with congestive heart failure, such that their benefits are attenuated when used in combination. Whether this interaction exists in patients with coronary artery disease is not known.

SUBJECTS AND METHODS

Patients enrolled in two large trials, Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO-I) and Evaluation in PTCA to Improve Long-Term Outcome with Abciximab GP IIb/IIIa Blockade (EPILOG), were stratified according to use of aspirin and ACE inhibitors on discharge from the hospital. In the EPILOG trial, left ventricular systolic function was assessed by contrast ventriculography. The primary endpoint was all-cause mortality at 1 year. EPILOG patients, all of whom were receiving aspirin, were also examined for the combined endpoint of death or nonfatal myocardial infarction. Stratified and multivariate analyses were used to adjust for baseline differences in patient characteristics.

RESULTS

We studied 31,622 patients in the GUSTO-I trial and 2,619 patients in the EPILOG trial. There were 615 deaths among the GUSTO-I patients and 45 deaths among the EPILOG patients at 1 year. Unadjusted mortality was greater among patients treated with both ACE inhibitors and aspirin than among patients treated with aspirin alone (3.3% versus 1.6%, P <0.001 for GUSTO-I; and 3.7% versus 1.2%, P <0.001 for EPILOG). Similarly, the composite endpoint of death or nonfatal myocardial infarction was more frequent among EPILOG patients who were taking ACE inhibitors (6.3% versus 3.3%, P = 0. 001). After adjusting for confounders, combined use of aspirin and ACE inhibitors was associated with increased mortality in GUSTO-I patients (hazard ratio [HR] = 2.2, 95% confidence interval [CI]: 1.1 to 4.3, P = 0.03) compared with aspirin alone. In EPILOG patients, after adjusting for clinical factors and extent of left ventricular dysfunction, the combination of aspirin and ACE inhibitors was associated with an increased risk of death (HR = 2.1, 95% CI: 1.1 to 3.8, P = 0.02) and of death or nonfatal myocardial infarction (HR = 1.5, 95% CI: 1.1 to 2.5, P = 0.02) compared with aspirin alone.

CONCLUSION

These observational findings suggest the possibility of an interaction between aspirin and ACE inhibitors among patients with ischemic heart disease. Further study of this issue is warranted.

Inhibitory activity of aspirin on von Willebrand factor-induced platelet aggregation

The effect of aspirin (ASA) on vWF induced platelet - platelet interaction is unknown. We therefore tested the response of platelets to von Willebrand factor (vWF) coated beads induced platelet aggregation before and after i.v. and oral ASA. 1000 mg ASA was infused to 10 healthy individuals and after a wash-out period 7 volunteers received 100 mg ASA orally over a period of 11 days. Prior to ASA and in regular intervals thereafter we tested the reactivity to vWF-coated beads to assess platelet adhesion/aggregation and the fade-out time of ASA effects on platelets. Considerable interindividual variability in response to vWF-coated beads was observed, both before ASA and after treatment with ASA. The maximal response to vWF-coated beads (Tmax), the time lag, and the slope of the curve were significantly affected by i.v. ASA, whereas 100 mg of ASA had only inconstant effect on Tmax and slope. The absolute reduction of Tmax after ASA depended on the pre-ASA level, while the percentage of the reduction was similar in all individuals. Thus, platelet aggregation induced by vWF-coated beads is impaired by ASA. Furthermore, our data indicate a large interindividual variability of the response to ASA shortly after treatment induction, which becomes more constant after prolonged treatment.

[In vitro effects of L-carnitine on the inhibition of sperm mobility induced by FANS]

OBJECTIVE

We wanted to study the function of some substances present in the seminal fluid (PG and L. Carnitine), which, with different mechanisms, affected Spermatozoa motility, and to study the effect of other substances (F.A.N.S.), known also for their action on P.G.

PATIENTS AND METHODS

Ten samples of seminal fluid from healthy subjects were studied according to the indications of the World Health Organization (1992).

RESULTS

All the F.A.N.S. used (Cinnoxicam, Salicylic Acetyl Acid) had an inhibitory effect on motility, as did L. Carnitine at high doses. We thought it interesting to observe if L. Carnitine added to the seminal fluid before F.A.N.S. blocked their effects.

CONCLUSIONS

The pre-treatment with L. Carnitine had an "in vitro" buffering effect on F.A.N.S.

Nonsteroidal anti-inflammatory drugs, COX-2 and colorectal cancer

Use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) has been associated with reduced risk of colorectal cancer. Moreover, the NSAID sulindac reduces the number and size of polyps in patients with familial adenomatous polyposis. The mechanisms of these effects of NSAIDs are not known but several lines of evidence suggest the involvement of the inhibition of the inducible isoform of prostaglandin H synthase (known as COX-2). Specific COX-2 inhibitors, showing an improved profile of gastrointestinal safety vis-à-vis conventional NSAIDs, provide interesting tools to probe the COX-2 dependence of the apparent protection against colorectal cancer associated with the use of NSAIDs.

PGHS-2 inhibitors, NS-398 and DuP-697, attenuate the inhibition of PGHS-1 by aspirin and indomethacin without altering its activity

Since the discovery of the inducible form of prostaglandin (PG) H synthase (PGHS), PGHS-2, considerable effort has been made to design selective inhibitors of this isozyme. N-(2-cyclohexyloxy-4-nitrophenyl) methanesulfonamide (NS-398) and 5-bromo-2-(4-fluorophenyl)-3-(4-methylsulfonyl) thiophene (DuP-697) have been shown to interact reversibly with PGHS-1, while irreversibly inhibiting PGHS-2 in a time-dependent manner. In the present study we have tested the effects of DuP-697 and NS-398 on the activity of PGHS-1 and further explored the interactions between these agents and the inhibition of PGHS-1 by aspirin, indomethacin and ibuprofen. Three independent experimental systems, namely bovine aortic endothelial cells (BAEC), human fibroblasts and ram seminal vesicle microsomes were used to investigate the effects of DuP-697 and NS-398 on PGHS-1. The results show that DuP-697 and NS-398, at concentrations ranges which do not inhibit PGHS-1 activity, significantly attenuated the inhibition of PGHS-1 that was caused by aspirin and indomethacin. The same concentrations of DuP-697 and NS-398 did not affect the inhibition of PGHS-1 that was induced by the competitive reversible inhibitors ibuprofen and naproxen. Similar effects of DuP-697 and NS-393 were obtained with ram seminal vesicle microsomes. These results suggest that PGHS-2 inhibitors DuP-697 and NS-398 possibly interact with PGHS-1 at a site different from the enzyme's catalytic site, thus causing attenuation of PGHS-1 inhibition by aspirin and indomethacin without altering PGHS-1 basal activity or the ibuprofen-induced inhibition.

[Antagonism of folic acid on the toxicity of aspirin in yolk sac of rats]

The antagonistic effects of folic acid to aspirin on the development of rat yolk sac and embryos were studied during early organogenesis by using whole embryo culture technique and electron microscopy. The results showed that when treated with aspirin, the diameter of yolk sac and the body length of embryo were much shorter, the frequencies of abnormal embryos were significantly higher, and the yolk sac became thinner than those without treatment. The number of blood islands and capillaries decreased, the differentiation and development of blood vessel were retarded in the treated group. Ultrastructure observation also showed that the numbers of microvilli and capillaries were greatly decreased, and the structure and the numbers of lysosomes, endoplasmic reticula and ribosomes significantly changed in the treated group. When aspirin was added with high folic acid serum, the toxicity on yolk sac decreased or disappeared. The results suggested that the protection of yolk sac would be related to the antagonism of folic acid to aspirin.

Salicylate-induced kidney mitochondrial permeability transition is prevented by cyclosporin A

The effect of salicylate, the active metabolite of aspirin (acetyl salicylic acid) in the presence of Ca2+ and phosphate on mitochondrial permeability transition (MPT) was studied. MPT is often associated with opening of a Ca2+ -induced pore. The opening of this pore leads to swelling, loss of mitochondrial membrane potential and release of accumulated Ca2+. In freshly isolated rat kidney mitochondria, salicylate (400 microM) in the presence of 20 nmol Ca2+/mg protein and 0.1 mM phosphate induced swelling, loss of mitochondrial membrane potential and release of accumulated Ca2+. All these changes were eliminated when cyclosporin A (1 microM), (a pore inhibitory agent) was included in the incubation medium. Unlike salicylate, unhydrolyzed aspirin (400 microM) induced these changes slightly. We concluded that salicylate acts as an activator of Ca2+ and phosphate in promoting the opening of kidney inner mitochondrial membrane pore. As a result a great consideration should be given to its toxicological effect.

Effect of vitamin E supplementation on prostaglandin concentrations in aspirin-induced acute gastric injury in aged rats

Nonsteroidal antiinflammatory drugs (NSAIDs), such as aspirin, frequently cause gastric mucosal injury in the elderly. Impairment of prostaglandin synthesis is a crucial step by which aspirin attenuates mucosal defense capacity. Vitamin E has been shown to decrease prostanoid concentrations, which implies an ulceropermissive effect of vitamin E. To assess the effect of vitamin E on aspirin-induced gastric injury and mucosal prostanoid concentrations, 20 male rats aged 20 mo were divided into two groups and fed diets containing either 30 (physiologic requirement) or 500 mg all-rac-alpha-tocopheryl acetate/kg. After 6 wk, all rats received two intragastric doses of aspirin (1.4 mumol/kg body wt). A third group of six animals fed the high-vitamin E diet received a vehicle solution without aspirin. Mucosal samples for vitamin E and prostaglandin E2, 6-keto-prostaglandin F1 alpha, and thromboxane A2 measurements were collected. The prevalence and degree of mucosal lesions were not significantly different among all groups. Rats fed the high-vitamin E diet had significantly higher mucosal vitamin E concentrations than rats fed the low-vitamin E diet. Mucosal concentrations of all three prostanoids were 95% lower in aspirin-treated rats than in controls (P = 0.0001 in all instances). The high-vitamin E diet group had significantly lower mucosal 6-keto-prostaglandin F1 alpha concentrations (P = 0.02) than the low-vitamin E diet group, indicating decreased prostacyclin formation, whereas concentrations of prostaglandin E2 and thromboxane A2 were similar in the aspirin-treated groups. Aspirin markedly reduced mucosal prostanoid concentrations in rats, without apparent effects on gastric injury, whereas vitamin E supplementation significantly reduced mucosal 6-keto-prostaglandin F(1 alpha) concentrations. Nevertheless, vitamin E supplementation did not result in more gastric injury in aspirin-treated rats than in controls.

Nitric oxide reverses aspirin antagonism of t-PA thrombolysis in a rabbit model of thromboembolic stroke

Randomized trials of thrombolytic therapy in stroke have reported an improvement in neurologic outcome; however, the addition of aspirin has resulted in a significant increase in mortality and antagonism of clot lysis in clinical and animal studies, respectively. This finding is in contradistinction to the known synergy in mortality reduction for aspirin and thrombolytics in myocardial infarction. It is hypothesized that aspirin antagonism of clot lysis is related to inhibition of nitric oxide (NO) and may be reversed by providing a source of NO. Twenty rabbits were treated with aspirin (20 mg/kg, i.v.) prior to internal carotid clot embolization. One-half hour following embolization, rabbits were randomized to receive vehicle (n = 5), the NO precursor L-arginine (300 mg/kg, i.v. bolus at 0.5 and 2.5 h postembolus; n = 5), or a nitric oxide donor (nitroprusside, 1 mg/kg/h, i.a., or nitroglycerin, 10 microg/kg/min, i.v., n = 5 each agent). Tissue plasminogen activator (t-PA) (6.3 mg/kg) was administered from 1 to 3 h after embolization. Lysis of the tin-tagged clot was followed with serial X rays and gross examination. No rabbit in the control group experienced complete clot lysis. However, 2 of 5 rabbits in the L-arginine group and 6 of 10 rabbits in the nitric oxide donor (nitroprusside and nitroglycerin) groups noted complete clot lysis (P < 0.05, Fisher exact test). Thus, administration of an NO donor (nitroglycerin or nitroprusside) and, to a lesser extent L-arginine, reversed aspirin's antagonism of t-PA thrombolysis. This study may help explain the discrepant results seen with aspirin and thrombolytics.

Serotonin and opiate involvement in the antinociceptive effect of acetylsalicylic acid

Acetylsalicylic acid (ASA), 400 mg/kg i.p., displayed antinociceptive activity in both the hot-plate and the formalin test. ASA significantly increased brain serotonin (5-HT) content and reduced the number of 5-HT2 receptors in cortical brain membranes 30 min after drug administration. Pretreatment with naloxone abolished the antinociceptive activity of both ASA and morphine in the hot-plate and formalin tests and prevented the increase in cerebral 5-HT concentration and the reduction in 5-HT2 receptors in cortical membranes induced by ASA. The serum salicylate concentrations were not affected by pretreatment with naloxone. These data indicate a central antinociceptive activity of ASA and suggest that ASA may exert its antinociceptive action through serotonergic and opiatergic pathways.

Interaction between enalapril and aspirin on mortality after acute myocardial infarction: subgroup analysis of the Cooperative New Scandinavian Enalapril Survival Study II (CONSENSUS II)

The use of angiotensin-converting enzyme (ACE) inhibitors early after an acute myocardial infarction to reduce mortality has been studied in several trials with inconsistent results. Aspirin (ASA) has become a well-documented therapeutic adjunct in patients with coronary heart disease. Attention has recently been focused on a possible interaction between ASA and ACE inhibitors. We therefore reanalyzed data from the Cooperative New Scandinavian Enalapril Survival Study II (CONSENSUS II) to find any evidence of differential effects of the ACE inhibitor enalapril in subgroups defined by use of ASA at baseline. Logistic regression tested the multiplicative interaction. We used Rothman synergy index S, which would be equal to unity under additivity, and less than unity when suggesting antagonism, to examine the postulated interaction with departure from an additive model. Logistic regression showed that the enalapril-ASA interaction term was a significant predictor of mortality at the end of the study (p = 0.047), and was a borderline significant predictor of mortality 30 days after randomization (p = 0.085). The Rothman synergy index S was 0.66 (95% confidence interval 0.46 to 0.94) for mortality at the end of the study, and 0.68 ( 0.44 to 1.04) for 30-day mortality, indicating antagonism between enalapril and ASA with departure from an additive model. Thus, we found evidence of enalapril-ASA interaction. The effect of enalapril was less favorable among patients taking ASA than among patients not taking ASA at baseline.

The alterations in the energy linked properties induced in rat liver mitochondria by acetylsalicylate are prevented by cyclosporin A or Mg2+

The alterations in rat liver mitochondria induced by acetylsalicylate in the presence of low concentrations of Ca2+ (large amplitude swelling, permeability to 14C]sucrose, collapse of transmembrane potential and effluxes of endogenous Mg2+ and accumulated Ca2+) were fully prevented by either cyclosporin A or Mg2+. Cyclosporin A and Mg2+ were also capable of restoring transmembrane potential upon its decrease induced by acetylsalicylate. The loss of endogenous Mg2+ was the primary effect promoted by acetylsalicylate; the other noxious effects followed. These results indicate that Mg2+ are fundamental components of the mitochondrial permeability barrier and that their loss might be responsible for the membrane transition induced by acetylsalicylate.

[Protective effect of omeprazole against low-dose acetylsalicylic acid. Endoscopic controlled double-blind study in healthy subjects]

Protective Effects of Omeprazole against Low-dose Acetylsalicylic Acid/An endoscopic controlled double-blind study in healthy volunteers. In a randomized double-blind parallel study the gastroduodenal tolerability of 300 mg acetylsalicylic acid (CAS 50-78-2, ASA) daily (8 p.m.) has been evaluated in the presence of 20 mg and 40 mg omeprazole (CAS 73590-58-6) daily (8 p.m.) or placebo in 36 healthy volunteers using upper GI-endoscopy. The treatment periods lasted 14 days. Endoscopic controls were performed at entry and repeated at day 14. At entry the mean endoscopic score averaged 0.9 +/- 0.08 in the ASA/placebo (n = 12), the ASA/omeprazole 20 mg (n = 12) and the ASA/omeprazole 40 mg group (n = 12). The median values were 1.0. In the placebo experiments 300 mg ASA daily induced marked gastroduodenal lesions at day 14 (12.4 +/- 1.7). The median value was 10.0. Concomitant administration of 20 mg omeprazole daily afforded significant protection against 300 mg ASA daily on day 14 (2.9 +/- 0.9) (p < 0.0005 vs. ASA/placebo). 300 mg ASA + 40 mg omeprazole daily reduced the damaging score to 1.8 +/- 0.5 (p < 0.00002 vs. ASA/placebo). The median values in the ASA/omeprazole 20 mg and in the ASA/omeprazole 40 mg group were 1.0. The difference in the damaging score between ASA/omeprazole 20 mg and ASA/omeprazole 40 mg after 14 days did not reach statistical significance. Our data suggest that coadministration of 20 mg omeprazole daily reduces almost completely gastroduodenal lesions evoked by 300 mg ASA.

DDAVP's shortening of the bleeding time seems due to plasma von Willebrand factor

The pathomechanism of desmopressin (DDAVP) dependent shortening of the acetylsalicylic acid (ASA) prolonged bleeding time (BT) is still unclear. The mechanism of action is supposed to be related to the plasma levels of von Willebrand factor (vWf), but a platelet effect is also discussed. We tried to investigate whether this effect of DDAVP might be due to either plasma vWF or platelets or both. We measured the effect of DDAVP (0.4 micrograms/ml bw in 250 ml 0.9% NaCl) on the Thrombostat 4000 (in vitro bleeding test (IVBT)) after each of 16 volunteers ingested 100 mg of ASA twice. To measure the possible effect of DDAVP on plasma and platelets separately, a mixture of 800 microliters of platelet poor plasma (PPP) or 200 microliters of isolated platelets after DDAVP, respectively, was prepared and the IVBT monitored. Two hundred microliters of PPP or platelets, respectively, served as a control. In an additional experiment, vWF concentrate (12 U/ml) dissolved in 200 microliters of PPP after ASA ingestion, as described above, was added to 800 microliters of citrated whole blood from the same volunteers. The addition of PPP after DDAVP as well as the PPP or PRP after ASA enriched with vWf led to a significant shortening of the IVBT in comparison to the control, indicating that the effect of DDAVP on the prolonged BT seems to be an isolated effect of plasma vWf. By adding platelets we were not able to show a direct effect of DDAVP on platelets.

Salicylamide reverses the aspirin-antagonistic effect of salicylic acid on rat platelet cyclooxygenase

The antagonistic effect of salicylic acid (SA), the major metabolite of aspirin, on aspirin (ASA)-induced inhibition of cyclooxygenase has been recognized in vivo and in vitro. Salicylamide is available with aspirin in some analgesic preparations. Salicylamide shares important characteristics with salicylic acid including the lack of effect on cyclooxygenase and platelet aggregation as well as a close structural resemblance. This prompted us to study the interaction of salicylamide with aspirin and/or SA on rat platelet and cyclooxygenase. Our results showed that salicylamide has, unlike SA, no blocking effect on the anticyclooxygenase effect of aspirin in vitro. Moreover, salicylamide could dose-dependently prevent the aspirin-blocking effect of SA on platelet cyclooxygenase. These results suggest that salicylamide and SA compete for a receptor on cyclooxygenase different to that of aspirin. A functional model of cyclooxygenase enzyme is proposed.