Systemic availability of acetylsalicylic acid in human subjects after oral ingestion of three different formulations

Aspirin may promote mitochondrial biogenesis via the production of hydrogen peroxide and the induction of Sirtuin1/PGC-1α genes

Based on the rapid hydrolysis of acetyl salicylic acid (ASA, Aspirin) to salicylic acid (SA), the ability of SA to form dihydroxy benzoic acid (DBA), and the latter's redox reactions to yield hydrogen peroxide (H(2)O(2)), we predicted that ASA may have the potential to induce Sirtuin1 (Sirt1) and its downstream effects. We observed that treatment of cultured liver cells with ASA resulted in the induction of Sirt1, peroxisome proliferator-activated receptor-gamma co-activator-1α (PGC-1α), and NAD(P)H quinone oxidoreductase 1 (Nqo1) genes. Paraoxonase 1 (PON1) and Aryl hydrocarbon receptor (AhR) siRNA transfections inhibited the induction of gene expressions by ASA suggesting the need for the acetyl ester hydrolysis and hydroxylation to DHBA. The latter also induced Sirt1, confirming the proposed pathway. As predicted, ASA and SA treatment resulted in the production of H(2)O(2), a known inducer of Sirt1 and confirmed in the current studies. More importantly, ASA treatment resulted in an increase in mitochondria as seen by tracking dyes. We suggest that DHBA, generated from ASA, via its oxidation/reduction reactions mediated by Nqo1 might be involved in the production of O(2)(-.) and H(2)O(2). As Sirt1 and PGC-1α profoundly affect mitochondrial metabolism and energy utilization, ASA may have therapeutic potential beyond its ability to inhibit cyclooxygenases.

Induction of paraoxonase 1 and apolipoprotein A-I gene expression by aspirin

Low-dose aspirin therapy has become a standard in the treatment of cardiovascular diseases. Aspirin has been shown to inhibit atherosclerosis in mouse models. To determine the mechanisms by which aspirin might inhibit atherosclerosis, we incubated HEPG2 cells and rat primary hepatocytes with aspirin or salicylic acid and noted an increase in paraoxonase 1(PON1) activity in the medium, together with an induction of PON1 and apolipoprotein A-I (apoA-I) gene expression. Mice treated with aspirin also showed a 2-fold increase in plasma PON1 activity and a significant induction of both PON1 and apoA-I gene expression in the liver. The induction of the PON1 gene in cell culture was accompanied by an increase in arylhydrocarbon receptor (AhR) gene expression. Accordingly, aspirin treatment of AhR(-/-) animals failed to induce PON1 gene expression. We previously suggested that aspirin might be hydrolyzed by serum PON1, which could account for its short plasma half-life of 10 min. Taken together with the current studies, we suggest that the antiatherosclerotic effects of aspirin might be mediated by its hydrolytic product salicylate and that the induction of PON1 and apoA-I might be important in the cardioprotective effects of aspirin.

Diclofenac potassium 12.5mg tablets for mild to moderate pain and fever: a review of its pharmacology, clinical efficacy and safety

Non-prescription (over-the-counter [OTC]) analgesics are used for the short-term treatment of acute painful conditions of mild to moderate intensity in everyday life. Well documented safety and efficacy, a rapid onset of action and a flexible daily dosing regimen are essential in this context. Film-coated, immediate-release, low-dose diclofenac potassium, developed for OTC use, offers a flexible daily dosing regimen with an initial dose of two tablets (2 x 12.5mg) followed by one or two tablets up to a maximum daily dose of six tablets (75 mg/day). The maximum plasma drug concentration is reached 30 minutes after administration, and the mean terminal half-life is 1-2 hours, allowing a 4- to 6-hour duration of activity, depending on the condition. Thirteen randomised, double-blind trials with both placebo and active controls have demonstrated the efficacy of diclofenac potassium 12.5mg tablets in conditions suitable for treatment with OTC medication, for example, acute lower back pain, headache, acute pain after dental extraction, symptoms of cold and influenza (including fever), and dysmenorrhoea. A single dose of diclofenac potassium 12.5mg is the lowest recommended effective dose. A two-tablet single dose of 25mg is at least as effective as ibuprofen 400mg. A flexible dosing regimen of an initial two tablets followed by one or two tablets up to a total daily dose of 75 mg is as effective as ibuprofen used in comparable fashion up to a total daily dose of 1200 mg. The incidence of adverse events in patients taking single or multiple doses of diclofenac potassium is similar to that of ibuprofen and placebo. In a safety study conducted to compare diclofenac potassium with ibuprofen for up to 3 months in patients with osteoarthritis of the knee, no differences in the pattern of adverse events were noted. There was no evidence of either hepatic injury or cardiovascular safety-related issues at any time during the study. Patients are generally capable of taking diclofenac potassium appropriately. A maximum OTC treatment duration of 5 days for pain and 3 days for fever is recommended.

Low dose acetylsalicylic acid in the antithrombotic treatment of patients with stable angina pectoris and acute coronary syndromes (unstable angina pectoris and acute myocardial infarction)

Acetylsalicylic acid has an antithrombotic effect by inhibition of thromboxane A2 synthesis in platelets. Thromboxane A2 is a potent stimulator of platelet aggregation and vasoconstriction and synthesis may be completely inhibited by a single oral dose of 150 mg acetylsalicylic acid or an intravenous dose of 100 mg. A daily maintenance dose of 75 mg acetylsalicylic acid is sufficient to effectively inhibit thromboxane A2 synthesis in long-term treatment. Acetylsalicylic acid therapy reduces acute myocardial infarction and sudden death in patients with stable angina pectoris and the drug is equally effective in patients with symptomatic and 'silent' angina pectoris. Early intervention with acetylsalicylic acid in patients with unstable angina pectoris reduces the risk of acute myocardial infarction and death. In patients with acute myocardial infarction, acute therapy with acetylsalicylic acid significantly reduces mortality both in monotherapy and in combination with thrombolytics. In the secondary prophylaxis following acute myocardial infarction, acetylsalicylic acid reduces the incidence of reinfarction and coronary death. Treatment of 100 patients with acute coronary syndrome (unstable angina pectoris or acute myocardial infarction) for 2 years may hinder the development of 3-4 fatal and 4 non-fatal vascular events. The risk of gastrointestinal side-effects and bleeding during acetylsalicylic acid therapy is dose-dependent and the incidence is low with a daily dose of 75-150 mg.

Preparation and analysis of deuterium-labeled aspirin: application to pharmacokinetic studies

Inhibition of endogenous prostacyclin and thromboxane biosynthesis by aspirin is critically dose-dependent in humans. Gastrointestinal and hepatic hydrolysis may limit systemic availability of aspirin, especially in low doses, perhaps contributing to the biochemical selectivity of aspirin. Existing analytical methods do not permit determination of systemic bioavailability when low (less than 100 mg) doses of aspirin are administered. Deuterium-labeled aspirin (2-acetoxy[3,4,5,6-2H4]benzoic acid) was synthesized from salicylic acid by catalytic exchange and subsequent acetylation. Analysis of the compounds as benzyl esters by GC-MS followed extractive alkylation from plasma. Heptadeuterated compounds were used as internal standards. Simultaneous administration of tetradeuterated aspirin intravenously with native aspirin orally to anesthetized dogs permitted kinetic studies of both aspirin and salicylic acid. The sensitivity of the method is superior to published methods using HPLC and, thus, more applicable to studies of low dose aspirin. Pulse administration of stable isotope-labeled aspirin permits detailed and repeated studies of dose-related aspirin pharmacokinetics in humans.

Systemic availability of acetylsalicylic acid in normal men and women and its effect on in vitro platelet aggregability

The systemic availability of acetylsalicylic acid (ASA) after oral ingestion of 1 g in an effervescent formulation was 16.3 +/- 2.0% and 16.9 +/- 3.2% of the ingested dose in normal women and men, respectively. The average plasma half-life of ASA in each sex was also identical at 18.5 +/- 1.4 and 18.1 +/- 1.2 min, respectively. The inhibitory effect of ASA on collagen-induced platelet aggregation in vitro on blood from both sexes was studied. The IC50 was 23.9 +/- 2.9 micrograms/ml in females and 22.5 +/- 2.7 micrograms/ml in males, which did not differ significantly. The inhibition by salicylic acid (SA) of the antiaggregatory effect of ASA was similar in both sexes with increases in IC50 to 33.5 +/- 5.1 micrograms/ml in females (p less than 0.02) and to 29.5 +/- 3.8 micrograms/ml in males (p less than 0.05). It is concluded that the observed sex-difference in the antithrombotic effect of ASA cannot be explained neither by differences between females and males in the pharmacokinetic properties of ASA after oral ingestion, nor by differences in the in vitro effect of ASA on the platelet aggregation induced by collagen.