Dose Of ASA Research Articles

The effect of aspirin on endothelial progenitor cell biology: Preliminary investigation of novel properties

Atherosclerosis develops in an environment of endothelial injury and inflammation. Circulating endothelial progenitor cells (EPCs) are required for vascular repair and restoration of normal endothelial function. We tested the hypothesis that the nonselective cyclooxygenase (COX) inhibitor aspirin (ASA) exerts an effect on circulating EPCs. Methods As part of a larger study evaluating the effect of aspirin dose in primary and secondary prevention, subjects (n = 32) were assigned randomly to either 81 mg or 325 mg aspirin daily for two months, and circulating mononuclear cells were enumerated at the beginning of the study and after 2 months using fluorescent antibodies against CD34 and CD133 as well as based on aldehyde dehydrogenase (ALDH) activity. Brachial artery endothelial function via flow-mediated dilation (BAFMD) and light transmittance platelet aggregometry in response to physiologic agonists was also determined. Results Subjects taking aspirin at the time of study entry had a lower numbers of CD133+/34+ cells compared to those not previously exposed (0.01% vs. 0.05% of MNCs, P < 0.03). After 2 months, subjects randomized to 81 vs. 325 mg of ASA had no significant differences in the median numbers of EPCs, although mean numbers trended lower in the high dose group. Patients on chronic ASA therapy continued to have lower numbers of EPCs. Similar effects were observed in CD34 and CD 133 single-positive cells, as well as ALDH br cells. BAFMD did not differ nor change significantly over time between aspirin dose groups. All patients had decreased ex vivo platelet aggregation in response to arachidonic acid and ADP stimulation. Conclusions Our preliminary studies suggest that aspirin exerts a time-dependent effect on circulating EPCs. Short-term exposure to differing doses of ASA had indeterminate effects on EPCs levels, suggesting that time of ASA exposure may play a more important role than dose. Determining the responsible mechanism(s) and the overall clinical relevance of these findings will require further investigation.

Abstract 5009: Prothrombotic Effect After Aspirin Discontinuation is Cox 2-dependent

Aspirin (ASA) discontinuation for surgery or non-compliance increases the risk of a thrombotic accident or stent thrombosis, especially after the second week. Previous papers have shown that 8 to 10 days after a single high dose of ASA in the rat, a pro-thrombotic state develops. We hypothesized that insignificant amounts of ASA may remain after discontinuation and cause a prothrombotic COX 2-mediated effect. Mehtods: Wistar rats (1000) were separated into 100 groups. Induced hemorrhagic time in seconds (IHT) and Laser-induced thrombosis, expressed as number of emboli (NE), were used. ASA was injected in 100 mg/kg, 1 mg/kg or 1/100 dilutions (Dil) 5, 9 or 15, subcutaneously, in a final volume of 1 ml/kg. Sterilized water was used as placebo. Selective inhibitors of COX 1 (SC-560) or COX 2 (NS-398) were used at 2.5, 5, 7.5 and 10 mg/kg, intragastrically. Carboxy-methyl-cellulose, the vehicle of COX inhibitors, was used as control. Each group was compared with its control with the t-test, p&lt;0.05 was considered significant. Results: (only highest or lowest doses shown) the highest dose of ASA prolonged IHT and decreased thrombosis. A clear opposite trend was observed with the highest dilution, which generated a shortened IHT and an increased NE. SC-560 produced an effect similar to the higher doses of ASA, prolonged IHT and decreased NE, proportional to dose increase. This effect of COX 1 inhibition was antagonized by the highest ASA dilutions. NS-398 created a pro-thrombotic effect that was antagonized by ASA at higher doses. There was no further effect of the highest dilution of ASA after NS-398. Conclusion: There is a clear prothrombotic effect of ASA Dil 15 that is opposed to COX 1 inhibition and which is inhibited by COX 2 inhibition. COX 2 inhibition and Dil 15 of ASA have similar effects. The prothrombotic effect of the highest dilution of ASA is achieved through COX 2 inhibition and may be blamed for the thrombotic accidents and stent thrombosis described after ASA discontinuation.

Low-dose ASA Response Using the PFA-100 in Women With High-risk Pregnancy

ObjectivesTo study the platelet function response to low-dose ASA with the Platelet Function Analyzer (PFA-100) in pregnant women and to identify maternal characteristics associated with non-responsiveness. MethodsWe conducted a prospective cohort study involving 87 pregnant women on ASA. The platelet function response to ASA was measured as the closure time obtained with epinephrine cartridges (CT-EPI) by the PFA-100. Non-response to ASA was defined as a CT-EPI ≤ 150 seconds after four weeks of therapy. Non-responders were given an escalating dose of ASA and their CT-EPI was tested again. ResultsAfter four weeks of enteric-coated ASA 81mg daily, 25/87 women (28.7%) were non-responders (95% CI 16.1 to 41.4). Among these women, a CT-EPI ≤ 150 seconds was found in 8/24 women (33.3%) after another four weeks of alternating ASA 81mg and 162mg daily. After a further four-week course of ASA 162mg daily, a CT-EPI ≤ 150 seconds was found in 3/6 women (50.0%). Among the women who initially responded and who were reassessed at 24–32 weeks of pregnancy, the CT-EPI was ≤ 150 seconds in 9/36 (25.0%). There was no statistical difference in maternal characteristics between ASA responders and non-responders. ConclusionA significant number of pregnant women showed a lack of platelet function response to ASA 81mg that was in most cases overcome with higher dosing. Furthermore, the prevalence of non-responsiveness increased with advancing pregnancy.

Incidence of Gastroduodenal Ulcers is Significantly Reduced When Analgesic Doses of Aspirin are Administered as PA65020, A Novel Combination of Enteric-Coated Aspirin (EC-ASA) and Immediate-Release (IR) Omeprazole

Purpose: To evaluate the gastroduodenal effects (via endoscopy) and safety profile of PA65020 vs. EC-ASA at analgesic doses. Methods: In a single-center, Phase 1, randomized, double-blind study, PA65020 (n=20) or EC-ASA 650 mg (n=20) was administered in the clinic twice daily for 28 days to healthy volunteers (≥50 yrs) with normal baseline endoscopy (Lanza score 0). Each dose of PA65020 was administered as one tablet of PA32520 [a fixed-dose combination tablet of EC-ASA 325 mg and IR omeprazole 20 mg] + one tablet of EC-ASA 325 mg. EC-ASA 650 mg was administered as 2 × EC-ASA 325 mg tablets. The total daily ASA dose was 1300 mg. Outcome evaluations included the occurrence of endoscopically proven gastric and/or duodenal lesions meeting Grade 3 or Grade 4 Lanza scores on Day 28 (primary endpoint), incidence of gastroduodenal ulcers (GU/DU), as well as assessments of dyspepsia-associated abdominal pain by mSODA (modified severity of dyspepsia assessment score, range 2-47), heartburn, and adverse events. Results: A total of 40 subjects (mean age 59.7 years) were treated. At Day 28, the incidence of Grade 3 or 4 Lanza scores was significantly less for the PA65020 group (3 [15%]) than for the EC-ASA 650 mg group (17 [85%]), P<0.001. The incidence of GU/DU on Day 28 was also significantly lower with PA65020 vs. EC-ASA 650 mg (0% vs. 40%, P=0.003). At Day 28, the mean change from baseline in mSODA was 0 for PA65020 and 0.7 for EC-ASA 650 mg. More PA65020 subjects were heartburn-free (90%) throughout the study compared with subjects in the EC-ASA 650 mg group (75%). The most commonly reported adverse events were GI-related, primarily dyspepsia (2 subjects in each treatment group) and stomach discomfort (3 subjects in the EC-ASA 650 mg group vs. 0 subjects in the PA65020 group). Conclusion: Analgesic doses of over-the-counter ASA produced significant mucosal damage in most subjects following 1 month of treatment. PA65020 is associated with a significantly decreased risk of GU/DU, and may provide an important option for at-risk patients who require analgesic doses of ASA. Disclosure: Drs. Fort and Plachetka - Employees and Stockholders: Pozen, Inc. Drs. Orlemans and Unal - Employees: Pozen, Inc.Table

The significantly enhanced frequency of functional CD4 +CD25 +Foxp3 + T regulatory cells in therapeutic dose aspirin-treated mice

CD4 +CD25 +Foxp3 + regulatory T (Treg) cells, produced in the thymus or periphery as a functionally mature T cell subpopulation, play pivotal roles in maintenance of self-tolerance and negative regulation of immune responses. Aspirin (ASA) is widely used to reduce pain, the risk of cardiovascular diseases and allo-graft rejection. However, the effect of ASA on CD4 +CD25 +Foxp3 + Treg cells has yet to be determined. The frequency, phenotype and immunosuppressive function of CD4 +CD25 +Foxp3 + Treg cells were detected in BALB/c mice treated with low or high doses of ASA for 4 weeks. ASA significantly decreased the percentage and number of CD4 + T cells in the periphery, while ASA remarkably increased the percentage of CD4 +CD25 +Foxp3 + Treg cells in CD4 +T cells. The total cell numbers of thymocytes were significantly decreased in ASA-treated mice, but the number of CD4 + CD25 +Fxop3 + cells and its ratio in CD4 +CD8 − thymocytes were markedly enhanced in the thymi of ASA-treated mice. The phenotype of CD4 +CD25 + Treg cells, including the expressions of CD44, CD45RB, CD62L, CD69, GITR and CTLA-4, did not show detectable changes in ASA-treated mice. CD4 +CD25 + Treg cells in ASA-treated mice exhibited unimpaired immunosuppressive function on CD4 +CD25 − T effector cells. ASA significantly enhanced the frequency of functional CD4 +CD25 +Foxp3 + Treg cells in mice in a therapeutic dose range. The different effects of ASA on CD4 +CD25 +Foxp3 + Treg cells and CD4 +CD25 − T cells may potentially make hosts susceptible to tolerance induction which would be beneficial for tolerance induction in patients with autoimmune diseases or allo-grafts. This study may have potential impacts in the clinical application of ASA.

Plasma Triglycerides as Predictors of Platelet Responsiveness to Aspirin in Patients after First Ischemic Stroke

Background: Although aspirin (ASA) remains the most popular and accepted agent for secondary stroke prevention, its efficacy does not exceed 25%. Platelet function monitoring in ASA users suggests that some individuals exhibit a reduced or even absent antiplatelet response after ASA. This phenomenon, also known as ‘resistance’, is prevalent in stroke survivors. We sought to evaluate the blood lipid profile in poststroke ASA users dependent on their antiplatelet response to ASA. Methods: Ninety-six consecutive ASA users after first-ever ischemic stroke confirmed by imaging were prospectively enrolled. The platelet function analyzer (PFA-100, Dade Behring, USA) was utilized to assess the response after ASA. The lipid profile (total cholesterol, high-density lipoprotein, low-density lipoprotein and triglycerides) was measured using the Cardiochek instrument (Polymer Technology, USA) from the autologuos blood samples. Results: The poststroke duration was 3–26 months, and all patients were treated with ASA for at least 3 months. The allowed daily ASA doses were from 75 up to 325 mg, with a mean of 158 mg. The mean age of the patients was 71 years, almost 60% were women, and over 85% of the patients were treated with statins. Thirty-seven patients were identified as low ASA responders, while 59 patients exhibited an adequate response. There were no differences between ASA responders and nonresponders with regard to demographics, clinical characteristics, risk factors and concomitant medications. The lipid profile biomarkers were similar between groups with the exception of triglycerides, which were significantly increased in the patients with ASA resistance, compared with ASA responders. Conclusion: The fact that hypertriglyceridemia affects platelet response to ASA has potential practical implications in light of growing evidence that ASA may exert antiplatelet properties beyond the cyclooxygenase pathway. The mechanism of such an association is unclear but may be related to the diminished platelet membrane fluidity and inability of ASA to downregulate such ‘strong’ protected platelets.

204: Aspirin Use Prior to Initiation of Therapy with a Proprietary Niacin Extended-Release Reduces Discontinuation Rates Due to Flushing

Synopsis: Niacin has beneficial effects across all elements of the lipid profile; however, flushing can limit long-term adherence to therapy. Aspirin (ASA) can mitigate niacininduced flushing. Purpose: To evaluate the effect of ASA use prior to initiation of niacin therapy on tolerability of a novel combination of a proprietary, niacin extended-release with simvastatin (NER/S) as determined by discontinuation rates due to flushing. Methods: Data from 403 patients, who reported aspirin use prior to randomization to NER/S 1000/20, 2000/20, 1000/40, or 2000/40 mg/d for 24 weeks from two international studies, SEACOAST I and II, were pooled for this analysis. All patients had mixed dyslipidemia, including elevated cardiac risk-adjusted non-HDL-C, and were niacin-treatment-naive. After the end of the study, patients were retrospectively categorized based on ASA use prior to randomization: (1) those taking any dose of ASA (ASA ) at randomization and (2) those not taking ASA (ASA ). Results: The ASA subgroup included 192 of the 403 patients (47.6%), of whom 40 patients (9.9%) used 325 mg/d ASA, 101 (25.1%) used 81 or 100 mg/d ASA, and 51 (12.7%) used other doses. Most ASA patients reported that the ASA was being taken for cardiovascular disease prevention, therefore, frequency of ASA use at baseline differed based on coronary heart disease (CHD) risk (p 0.001 compared with ASA ). Of 271 patients with CHD or its risk equivalent, 164 (60.5%) used ASA; 24 of 100 patients (24.0%) with 2 risk factors used ASA; and 4 of 32 patients (12.5%) with 0 –1 risk factors used ASA. During NER/S treatment, fewer ASA than ASA patients experienced 1 flushing episode, 54.2% and 62.1%, respectively. Discontinuation rates due to flushing at week 24 were lower in ASA versus ASA patients, 4.2% and 7.6%, respectively. Of the 40 patients using 325 mg/d ASA at baseline, only one (2.5%) discontinued NER/S due to flushing. Treatment-emergent adverse events classified within the gastrointestinal system-organ class occurred with similar frequency in ASA and ASA patients (17.7% and 13.3%, respectively; p 0.27); no individual gastrointestinal adverse events occurred more frequently in ASA versus ASA patients (all p 0.1). Conclusions: Flushing and discontinuation due to flushing tended to be reduced in subjects reporting use of cardioprotective ASA before niacin therapy, suggesting that prior experience with ASA improves niacin tolerability. Relationships between ASA use and niacin persistence should be further explored in prospective studies.

W1932 Gastroprotective Strategies Are Underutilized in High-Risk Patients Using Cardioprotective Doses of Aspirin

Background: The upper gastrointestinal (UGI) risk associated with over-the-counter (OTC) non-steroidal anti-inflammatory drugs (NSAID) and aspirin (ASA) use remains unclear. Purpose: Quantify the potential risk of endoscopically visualized lesions to the upper gastrointestinal tract after ingestion of ASA, ibuprofen, naproxen, and ketoprofen at the Federal Drug Administration approved dosage for sale without a prescription. Methods: Using a standardized search strategy, two independent investigators searched PubMed, EBSCO, and Medline databases to identify all English-language studies published from 19662006. All studies met a priori inclusion criteria of trials examining the primary endpoint of endoscopically visualized UGI lesion, defined as ulceration of the stomach and duodenum with associated hemorrhage, gastritis, or perforation after consumption of OTC NSAID or ASA. All potential studies were scored for methodological quality using validated scoring systems (The Jadad score and the Downs & Black), then independently abstracted for the outcome of interest. Clinical studies of similar quality were pooled and compared using random effects modeling to calculate a relative risk (RR) or adjusted odds ratio (OR) with 95% confidence intervals (CI). The heterogeneity was calculated using the I2 statistic. Results: Eight randomized control trials (RCT), ten case-control trials, and five cohort studies met the inclusion criteria and were of comparative study quality. Pooled estimates of the seven RCTs for OTC NSAID and ASA (n=387) revealed greater than four-fold increased risk of UGI lesion when compared to placebo (RR, 4.71; 95% CI, 3.13-7.08; p<0.00001; I2 = 0%). The six case-control studies (n=867 cases; n=5623 controls) produced similarly significant results with a pooled OR of 2.2 (95% CI, 1.93-2.54; p<0.00001; I2=44.2%). Subgroup analysis OTC NSAIDs alone versus placebo (3 RCTs, n=172) demonstrated a RR of 4.41 (95% CI, 2.14-9.10; p<0.0001; I2=0%). Results from six case-controlled ASA trials using doses of less than 325mg suggested a near two-fold increased risk of UGI lesion (OR, 1.94; 95% CI, 1.75-2.16; p<0.00001; I2 = 0%) when compared to controls. Similar results were noted in the eight case-control arms that used adjusted multivariate risk ratios (RR, 2.87; 95% CI, 2.42-3.39; p<0.00001; I2 = 0%). Conclusion: Consumption of OTC doses of NSAID and ASA increases the risk of endoscopically visualized UGI lesions twoto fourfold when compared to placebo. The clinical significance of these lesions remains unclear, and further studies will need to be completed to assess if these lesions pose a significant risk to the patient.

Secondary Stroke Prevention - Recent Advances: Subtherapeutic Dosage

The authors do not mention that in ESPRIT – in the comparison between dipyramidole+ASA versus ASA – a substantial proportion of patients did not receive sufficiently high doses of ASA (< 75 mg/day). It is correct to state that in case of subtherapeutic ASA dosage, additional dipyramidole offers protection from serious events, with an NNT of 80 per year. This statement is far removed from clinical practice and does not benefit patients, and the NNT is not impressive either.

Clinical Outcomes of Palliative Surgery Including a Systemic-to-Pulmonary Artery Shunt in Infants With Cyanotic Congenital Heart Disease

Aspirin (ASA) often is used to prevent thrombosis in infants with congenital heart disease after placement of a systemic-to-pulmonary artery shunt, but its effect on outcomes is unknown. The present multicenter study prospectively collected data on 1-year postoperative rates of death, shunt thrombosis, or hospitalization age <4 months for bidirectional Glenn/hemi-Fontan surgery in 1004 infants. The use and dose of ASA were recorded. Kaplan-Meier event rates were calculated for each event and the composite outcome, and a Cox regression model was constructed for time to event. Model terms were ASA use and type of surgery, with adjustment for age at surgery. Diagnoses were hypoplastic left heart syndrome (n=346), tricuspid atresia (n=103), tetralogy of Fallot (n=127), pulmonary atresia (n=177), heterotaxy syndrome (n=38), and other (n=213). There were 344 shunts placed without cardiopulmonary bypass (closed shunt), 287 shunts with bypass (open shunt), 323 Norwood procedures, and 50 Sano procedures. Overall, 80% of patients received ASA. One-year postoperative events rates were high: 38% for the composite end point, 26% for death, and 12% for shunt thrombosis. After the exclusion of patients with early mortality, patients receiving ASA had a lower risk of shunt thrombosis (hazard ratio, 0.13; P=0.008) and death (closed shunt: hazard ratio, 0.41, P=0.057; open shunt: hazard ratio, 0.10, P<0.001; Norwood: hazard ratio, 0.34, P<0.001; Sano: hazard ratio, 0.68, P=NS) compared with those not receiving ASA. The morbidity and mortality for infants after surgical placement of a systemic-to-pulmonary artery shunt are high. ASA appears to lower the risk of death and shunt thrombosis in the present observational study.

Salicylates Trigger Protein Synthesis Inhibition in a Protein Kinase R-like Endoplasmic Reticulum Kinase-dependent Manner

The non-steroidal anti-inflammatory drug aspirin and its metabolite, sodium salicylate, have profound effects on cellular protein synthesis and cell physiology. However, the underlying mechanism by which they cause these responses remains unclear. We show here that salicylates induce phosphorylation of the alpha-subunit of eukaryotic translation initiation factor 2 (eIF2alpha), resulting in the inhibition of mRNA translation in cells. Exposure of cells to acetyl salicylic acid resulted in strong activation of eIF2alpha stress-activated protein kinase R-like endoplasmic reticulum kinase (PERK). Analysis of fibroblasts with a targeted deletion of the perk gene revealed that PERK is indispensable for triggering the phosphorylation of eIF2alpha as well as the inhibition of protein synthesis induced by salicylates. Although salicylate treatment did not trigger activation of inositol-requiring enzyme 1, there was an increased expression of the pro-apoptotic transcription factor CHOP-(gadd153), a downstream event to eIF2alpha phosphorylation known to mediate endoplasmic reticulum stress-mediated responses. Thus, salicylates selectively trigger an endoplasmic reticulum stress-responsive signaling pathway initiated through activation of PERK to induce their cellular effects.

Aspirin before reperfusion blunts the infarct size limiting effect of atorvastatin

We assessed whether aspirin (acetylsalicylic acid, ASA), administered before reperfusion, abrogates the infarct size (IS)-limiting effect of atorvastatin (ATV). Statins reduce IS. This dose-dependent effect is mediated by upregulation of cycloxygenase-2 (COX2) and PGI(2) production. Administration of selective COX2-inhibitors either with ATV for 3 days or immediately before coronary occlusion blocks the IS-limiting effect of ATV. Sprague-Dawley rats received 3-day ATV (10 mg x kg(-1) x day(-1)) or water alone. Rats underwent 30 min coronary artery occlusion and 4 h reperfusion (IS protocol, n=8 in each group), or rats underwent 30 min coronary artery occlusion and 10 min reperfusion (enzyme expression and activity protocol, n=4 in each group). Immediately before reperfusion rats received intravenous ASA (5, 10, or 20 mg/kg) or saline. Area-at-risk (AR) was assessed by blue dye and IS by triphenyltetrazolium chloride. ATV reduced IS (10.1 +/- 1.4% of the AR) compared with controls (31.0 +/- 2.2%). Intravenous ASA alone did not affect IS (29.0 +/- 2.6%); however, ASA dose dependently (5, 10, and 20 mg/kg) attenuated the protective effect of ATV on IS (15.8 +/- 0.9%, 22.0 +/- 1.6%, and 23.7 +/- 3.8%, respectively). ASA dose dependently blocked the upregulation of COX2 by ATV. COX2 activity was as follows: control, 8.93 +/- 0.90 pg/mg; ATV, 75.85 +/- 1.08 pg/mg; ATV + ASA5, 34.39 +/- 1.48 pg/mg; ATV + ASA10, 19.87 +/- 1.10 pg/mg; and ATV + ASA20, 9.36 +/- 0.94 pg/mg. ASA, administered before reperfusion in doses comparable to those used in the clinical setting, abrogates the IS-limiting effect of ATV in a model with mechanical occlusion of the coronary artery. This potential adverse interaction should be further investigated in the clinical setting of acute coronary syndromes.

The Severity of Historical ASA/NSAID-Induced Asthma Attacks Does Not Correlate with Severity of Asthma Induced During Oral ASA Challenges

Attacks Does Not Correlate with Severity of Asthma Induced During Oral ASA Challenges A. N. Williams, R. A. Simon, K. M. Woessner, D. D. Stevenson; Scripps Clinic, San Diego, CA. RATIONALE: Historical aspirin (ASA) or nonsteroidal antiinflammatory drug (NSAID)-induced reactions might provide predictive information about the severity of reactions in patients with aspirin exacerbated respiratory disease (AERD) undergoing oral ASA challenges (OAC). METHODS: The provoking doses, treatments, and treatment settings of the historical ASA/NSAID-induced asthma attacks was obtained from 210 consecutive patients with suspected AERD referred for OAC and ASA desensitization. RESULTS: Of 210 subjects, 147 (70%) reported seeking acute medical care for their historical ASA/NSAID-induced asthma attacks. Of these 147, 101 (69%) were treated in ERs and released and 46 (31%) required hospitalization. During OAC in these 147 subjects, 37 (25%) had a >20% decline and 14 (10%) had a >30% decline in FEV1 values. Of the 46 patients previously hospitalized for ASA/NSAID-induced asthma attacks, 15 (33%) had a >20% decline and 6 (13%) had a >30% decline in FEV1 during OAC. By contrast, of the 63 patients who treated their prior ASA/NSAID-induced reactions at home, 10 (16%) had a >20% decline and 5 (8%) had a >30% decline in FEV1 during OAC (p value NS for both). The average provoking doses of ASA were 550 mg for the historical reaction and 62 mg during OAC. CONCLUSIONS: The severity of the historical ASA/NSAID-induced asthma attack was not helpful in predicting asthma severity during OAC. Even though 70% of patients sought acute medical care for asthma attacks provoked by therapeutic doses of ASA/NSAID, a minority had clinically significant asthma during low-dose OAC. These data provide further reassurance regarding the safety of outpatient ASA desensitization. Funding: General Clinical Research Center, Scripps Clinic

Relationships between the adverse effects of drugs and genetic polymorphism in genes encoding drug metabolizing enzymes

Van Oijen et al. reported in the Journal [1] an investigation which aimed to ‘assess whether polymorphisms in UGT1A6 and CYP2C9 were related to the prevalence of upper gastrointestinal symptoms in cardiovascular patients using acetylsalicylic acid for the secondary prevention of ischaemic heart disease’. The study was based on the assertion that UGT1A6 and CYP2C9 mediate the glucuronidation and hydroxylation of acetylsalicylic acid (aspirin; ASA), respectively, although no references were provided to support this proposition. There was no significant association between UGT1A6 and CYP2C9 genotypes and the incidence of gastrointestinal adverse effects in 160 patients receiving ASA. Not discounting other important issues associated with the study, particularly unavailability of the ASA dose(s) received by patients, we wish to comment on the theoretical basis for the investigation. The metabolism of ASA is well characterized (reviewed in [2]). ASA itself is not glucuronidated or hydroxylated. Rather, ASA is hydrolyzed to the pharmacologically active salicylic acid (SA) by esterases in the gastrointestinal tract and liver, and only approximately 50–70% of the dose reaches the systemic circulation as unchanged drug following oral administration. ASA escaping first pass extraction is rapidly hydrolyzed to SA with a half-life of about 15 min. Once formed, SA is metabolized to salicyluric acid (SUA; the glycine conjugate), phenolic- (SPG) and acyl- (SAG) glucuronides, and gentisic acid (2,5-dihydroxybenzoic acid; GA). SUA is the major metabolite of SA. In subjects administered 900 mg of ASA, SUA accounted on average for 68% of the dose recovered in urine [3]. SA, SPG, SAG and GA accounted for 12.2%, 10.6%, 8.2% and 1.4% of the recovered dose, respectively. Although formation clearances of SUA and SPG are known to be dose-dependent [4], SA clearance via the SUA pathway is, on average, about three-fold higher than by glucuronidation while hydroxylation to form GA represents a very minor pathway of SA elimination. In contrast to ASA, the elimination half-life of SA (the precursor of GA and the glucuronide conjugates) ranges from a few hours to almost 1 day, depending on the dose. SUA is formed in a two-step process; the first, and activating, step involves formation of a CoA thioester (mediated by a ‘medium chain’ CoA ligase) which is subsequently acylated by glycine N-acyltransferase. The UDP-glucuronosyltransferase(s) (UGT) involved in SA metabolism has not been characterized unambiguously. Ciotti et al.[5] reported that recombinant UGT1A6 glucuronidated SA, but activity was very low (0.05 pmol glucuronide min−1) and relative formation of SPG and SAG was not assessed. More recently, multiple UGTs have been shown to have the capacity to catalyze both the phenolic and acyl glucuronidation of SA [6]; these include UGT 1A1, 1A3, 1A6, 1A7, 1A9, 1A10, 2B4 and 2B7. (It should be noted that UGT 1A7 and 1A10 appear to be expressed only in the gastrointestinal tract, while the other forms are expressed in liver and variably in other tissues). It was not possible from the data presented to ascertain the dominant UGT(s) involved in SPG and SAG formation. To the best of our knowledge, the role of CYP2C9 and other P450s in GA formation has not been assessed in a systematic manner. Thus, the conclusions of van Oijen et al.[1] are hardly surprising. Glucuronidation accounts, on average, for about 20% of SA metabolic clearance and UGT1A6 appears to be just one of several enzymes involved in SAG and SPG formation. GA is a very minor metabolite of SA (approx. 1%) and a role for CYP2C9 as the principal catalyst for the conversion of SA to GA has not apparently been demonstrated. Other studies have also investigated relationships between ASA response and CYP2C9 and UGT1A6 polymorphisms. Bigler et al.[7] reported an inverse relationship between colon adenoma risk and ASA ‘use’ in subjects with a CYP2C9*1/variant UGT1A6 genotype. In contrast, McGreavey et al.[8] found that polymorphisms in CYP2C9 and UGT1A6 (and some other genes) did not influence the protective effect of NSAIDs, either including or excluding ASA use, on the risk of colorectal cancer. Relationships between mutations in genes encoding xenobiotic metabolizing enzyme(s) and the response to compounds eliminated or metabolically activated by a polymorphic enzyme (e.g. CYP2C9, CYP2D6, UGT1A1) have been demonstrated in numerous studies. However, clinically meaningful, generalizable conclusions should not be expected from pharmacogenetic studies based on flawed knowledge of the enzyme(s) responsible for metabolite formation and where the relative contribution of the metabolic pathway to overall elimination (e.g. GA formation) is negligible.

Consensus Development Conference on the Use of Nonsteroidal Anti-Inflammatory Agents, Including Cyclooxygenase-2 Enzyme Inhibitors and Aspirin

Consensus Development Conference on the Use of Nonsteroidal Anti-Inflammatory Agents, Including Cyclooxygenase-2 Enzyme Inhibitors and Aspirin

The effect of aspirin and vitamins C and E on HbA 1c assays

Background Aspirin (ASA) and vitamins C and E may inhibit non-enzymatic glycation in vivo and may also interfere with HbA 1c assays, masking true results. We investigated the effect of usual doses of ASA, vitamin C and E on HbA1c levels in a group of non-diabetic volunteers. Methods A randomized clinical trial was performed with 28 healthy non-diabetic individuals. Subjects were allocated to take ASA 200 mg/day, vitamin C 1 g/day, vitamin E 400 mg/day, or to a control group, for a period of 4 months. Blood samples were collected at baseline and at monthly intervals for HbA1c analysis by HPLC Variant II (BioRad), HPLC L-9100 (Merck – Hitachi) and Tina Quant® HbA 1c II immunoassay (Roche). Results HbA 1c levels of the control, vitamin C and E groups did not change throughout the study, independently of the method used. HbA 1c measured by Hitachi L-9100 HPLC increased significantly ( P = 0.033) at 4 months after ASA intake, although this increase was of only 0.17%. Conclusions: Treatment with vitamins C and E in pharmacological doses does not have any impact on HbA1c measurements in non-diabetic patients with the three methods employed. ASA induces a modest, not clinically relevant, increase in HbA1c levels with one of the methods.

Combined aspirin and Clopidogrel resistance associated with recurrent coronary stent thrombosis

We report about a 72-year-old woman who was admitted to our hospital because of an acute ST-elevation myocardial infarction (STEMI). At admission, she received a loading dose of 300 mg Clopidogrel and 500 mg aspirin (ASA) prior to angioplasty with stenting of a 90% diameter stenosis of the proximal right coronary artery. After intervention, 75 mg Clopidogrel and 300 mg ASA OD were continued. Three days later, she developed a recurrent acute STEMI due to stent thrombosis and a second stent implantation was performed. The dose of Clopidogrel and ASA remained unchanged. Three days later, the patient suffered a third STEMI due to a restent thrombosis and additional stent implantation was performed. The dose of Clopidogrel and ASA was increased to 75 mg BD and 500 mg OD. Platelet function analysis and aggregation studies demonstrated dose-independent ASA resistance. ADP-induced aggregation showed a short-term platelet inhibition with subsequent rapid normalisation, thus suggesting Clopidogrel resistance. Therefore, the treatment was changed to coumadin and ASA 100 mg OD. Since then, the patient has been clinically stabile. Our case indicates for the first time the existence of a subgroup of patients with combined Clopidogrel and ASA resistance. We conclude that identification of these patients is required and alternative therapeutic options have to be considered.

Apoptosis Induced by Aspirin and 5-Fluorouracil in Human Colonic Adenocarcinoma Cells

Various biochemical, clinical and epidemiological studies have shown that aspirin (ASA) and other nonsteroidal anti-inflammatory drugs (NSAIDs) demonstrate antineoplastic properties, particularly in the gastrointestinal tract, inhibiting the proliferation of colorectal cancer cells. The mechanism of action may be prostaglandin mediated through inhibition of the COX enzymatic system. This includes two iso-enzymes, COX-I and COX-II, working in concert with the activation of apoptosis, activation of immune surveillance, inhibition of proliferation, and inhibition of carcinogen activation. 5-Fluorouracil (5-FU) has demonstrated activity against colorectal cancer, leading to apoptosis of neoplastic cells. We evaluated the effects of varying doses of ASA (0.5, 1, 1.5 mM), both as a single agent and in combination with 5-FU (50 microg) in HT-29, a colon adenocarcinoma cell line. Proliferation assays showed that aspirin at a concentration of 1 mM inhibits cell growth. Cells treated with ASA, both alone and in combination with 5-FU, demonstrated apoptotic activity with the up-regulation of Bax protein, which is consistent with 5-FU anticancer treatment. Furthermore, there was synergistic cell death with ASA and 5-FU. DNA fragmentation, TUNEL, and trypan blue exclusion methods indicated that a combination of ASA and 5-FU induces apoptosis in cells in a time- and concentration-dependent manner. This study serves to further elucidate the mechanism of action of ASA, and ASA in combination with 5-FU, in colorectal cancer as evidenced by its effect on the HT-29 cell line.

The PFA-100® detects sub-optimal antiplatelet responses in patients on aspirin

Although it is suspected that some patients with acute coronary syndromes (ACS) could have a sub-optimal response to aspirin (SASAR), currently a fixed dose of ASA is long-term used in all individuals. This study was designed to determine SASAR and whether a SASAR is a predictor for recurrence of ischemic events in patients on low-dose ASA with a previous ACS. One hundred patients taking ASA 100 mg/day were assessed at 1 and 6 months after a first ACS. SASAR was initially defined as a failure of the ASA treatment to significantly prolong the closure time in the Platelet Function Analyzer (PFA-100®). SASAR in these samples was reconfirmed by conventional aggregometry. TXB2 levels were determined in plasma. At one month 49 patients showed SASAR in the PFA-100®; only 25 of them showed SASAR by conventional aggregometry. At six months, 39 of 81 patients showed SASAR by PFA-100®, but conventional aggregometry detected SASAR in only 12 of the 39 patients. TXB2 levels were significantly higher in patients with SASAR. Five patients with SASAR, by both tests, died during follow-up (p=0.013). The PFA-100® detected a high rate of SASAR in patients with ACS. This instrument could be used to screen for suboptimal response to the antiplatelet action of ASA. Whether persistence of SASAR could relate to a higher risk of recurrence and how adjusting the dose of ASA could reduce the rate of SASAR are issues that deserve further investigations.

Approach to "aspirin allergy" in cardiovascular patients.

Aspirin (ASA), by irreversibly inhibiting platelet cyclooxygenase-1 enzyme (COX-1), prevents platelet aggregation and is the mainstay of pharmacotherapy of patients with coronary artery disease (CAD). Long-term ASA therapy reduces mortality in CAD patients after an initial coronary event. Periprocedural ASA therapy significantly reduces major adverse cardiovascular events (MACE) after percutaneous coronary interventions.1,2 Despite a plethora of clinical data showing marked efficacy of ASA therapy in cardiovascular patients, ASA use continues to be less than optimal in real-world registries.3,4 A history of adverse reactions to ASA may prevent long-term use in a cardiovascular patient, thereby reducing optimal event protection. Most adverse reactions to ASA, such as gastrointestinal intolerance, are predictable and are dose and host related.5 However, ASA can also cause a hypersensitivity reaction, of which there are 3 types: respiratory sensitivity (asthma and/or rhinitis), cutaneous sensitivity (urticaria and/or angioedema), and systemic sensitivity (anaphylactoid reaction).6 Various terms have been used to describe the hypersensitivity reactions to ASA, including ASA intolerance, ASA idiosyncrasy, pseudoallergic reactions, and ASA sensitivity.7 The prevalence of ASA sensitivity in cardiovascular patients is not well known. Besides substitution with an alternative class of antiplatelet agents such as thienopyridines, ASA desensitization is an option for ASA-allergic patients who require long-term therapy for cardiovascular diseases.7 In this article, we review various hypersensitivity reactions to ASA and discuss desensitization protocols to allow ASA therapy in ASA-sensitive cardiovascular patients. ### ASA-Exacerbated Respiratory Disease ASA-exacerbated respiratory disease (AERD) is a triad of asthma, ASA sensitivity, and rhinitis/nasal polyps. Patients with AERD have aggressive mucosal inflammation and suffer from precipitation of asthma and rhinitis after ingestion of ASA and nonsteroidal antiinflammatory drugs (NSAIDs).8 AERD is also commonly referred to as ASA-sensitive, ASA-induced, or ASA-intolerant asthma. AERD is the cause of 10% to 15% of all cases of asthma,8 is usually …