Acetylsalicylic acid

Absorption

Absorption is generally rapid and complete following oral administration but absorption may be variable depending on the route, dosage form, and other factors including but not limited to the rate of tablet dissolution, gastric contents, gastric emptying time, and gastric pH .
Detailed absorption information
When ingested orally, acetylsalicylic acid is rapidly absorbed in both the stomach and proximal small intestine. The non-ionized acetylsalicylic acid passes through the stomach lining by passive diffusion. Ideal absorption of salicylate in the stomach occurs in the pH range of 2.15 - 4.10. Intestinal absorption of acetylsalicylic acid occurs at a much faster rate. At least half of the ingested dose is hydrolyzed to salicylic acid in the first-hour post-ingestion by esterases found in the gastrointestinal tract. Peak plasma salicylate concentrations occur between 1-2 hours post-administration .

Toxicity

Lethal doses
Acute oral LD50 values have been reported as over 1.0 g/kg in humans, cats, and dogs, 0.92 g/kg - 1.48 g/kg in albino rats, 1.19 g/kg in guinea pigs, 1.1 g/kg in mice, and 1.8 g/kg in rabbit models .
Acute toxicity
Salicylate toxicity is a problem that may develop with both acute and chronic salicylate exposure . Multiple organ systems may be affected by salicylate toxicity, including the central nervous system, the pulmonary system, and the gastrointestinal system. Severe bleeding may occur. In the majority of cases, patients suffering from salicylate toxicity are volume-depleted at the time of presentation for medical attention. Fluid resuscitation should occur immediately and volume status should be monitored closely. Disruptions in acid-base balance are frequent in ASA toxicity .
The acute toxicity of acetylsalicylic in animals has been widely studied. The signs of poisoning in rats from lethal doses are mild to severe gastroenteritis, hepatitis, nephritis, pulmonary edema, encephalopathy, shock and some toxic effects on other organs and tissues. Mortality has been observed following convulsions or cardiovascular shock. An important differentiating property between various animal species is the ability to vomit toxic doses. Humans, cats and dogs have this ability, but rodents or rabbits do not .
Chronic toxicity and carcinogenesis
Chronic ASA toxicity is frequently accompanied by atypical clinical presentations that may be similar to diabetic ketoacidosis, delirium, cerebrovascular accident (CVA), myocardial infarction (MI) or cardiac failure. Plasma salicylate concentrations should be measured if salicylate intoxication is suspected, even if there no documentation available to suggest ASA was ingested. In older age, nephrotoxicity from salicylates increases, and the risk of upper gastrointestinal hemorrhage is increased, with higher rates of mortality . It is also important to note that ASA toxicity may occur even with close to normal serum concentrations. Prevention of chronic ASA includes the administration of smallest possible doses, avoidance of concurrent use of salicylate drugs, and therapeutic drug monitoring. Renal function should be regularly monitored and screening for gastrointestinal bleeding should be done at regular intervals .
Chronic toxicity studies were performed in rodents. ASA was administered at doses measured to be 2 to 20 times the maximum tolerated clinical dose to mice for up to one year. Negative dose-related effects were seen. These include decreased mean survival time, decreased number of births and progeny reaching an appropriate age for weaning. No evidence of carcinogenesis was found in 1-year studies . At daily doses of 0.24 g/kg/day given for 100 days to albino rats, ASA led to signs to excessive thirst, aciduria, diuresis, drowsiness, hyperreflexia, piloerection, changes in respiration, tachycardia, followed by soft stools, epistaxis, sialorrhea, dacryorrhea and mortality during hypothermic coma in the second study month .
Use in pregnancy and lactation
While teratogenic effects were observed in animals nearly lethal doses, no evidence suggests that this drug is teratogenic in humans . It is advisable, however, to avoid ASA use the first and second trimester of pregnancy, unless it is clearly required. If acetylsalicylic acid containing drugs are ingested by a patient attempting to conceive, or during the first and second trimester of pregnancy, the lowest possible dose at the shortest possible duration should be taken . This drug is contraindicated in the 3rd trimester of pregnancy .

Description

Acetylsalicylic acid is a white crystalline powder commonly known by its common name as aspirin or ASA. Aspirin is the most widely used medication in the world.

Description

Aspirin, or more formally, acetylsalicylic acid, was first identified and prepared by C. F. Gerhardt in 1853. By 1899, Bayer was manufacturing it and selling it worldwide. It was the leading over-the-counter pain remedy until the 1950s, when acetaminophen and then ibuprofen began to take away much of its market. In the 1980s, the discovery that aspirin is an anticlotting agent strengthened its sales because many people take it to lower the chance of heart attack or stroke.

The Uses of Acetylsalicylic acid

Acetylsalicylic acid's original use as an analgesic, an antipyretic, and to reduce inflammation continues to this day. More recently there is some evidence that aspirin lessens the chance of heart attacks as a result of its effect as a blood "thinner."

Background

Also known as Aspirin, acetylsalicylic acid (ASA) is a commonly used drug for the treatment of pain and fever due to various causes. Acetylsalicylic acid has both anti-inflammatory and antipyretic effects. This drug also inhibits platelet aggregation and is used in the prevention of blood clots stroke, and myocardial infarction (MI) .
Interestingly, the results of various studies have demonstrated that long-term use of acetylsalicylic acid may decrease the risk of various cancers, including colorectal, esophageal, breast, lung, prostate, liver and skin cancer . Aspirin is classified as a non-selective cyclooxygenase (COX) inhibitor and is available in many doses and forms, including chewable tablets, suppositories, extended release formulations, and others .
Acetylsalicylic acid is a very common cause of accidental poisoning in young children. It should be kept out of reach from young children, toddlers, and infants .

Indications

Pain, fever, and inflammation
Acetylsalicylic acid (ASA), in the regular tablet form (immediate-release), is indicated to relieve pain, fever, and inflammation associated with many conditions, including the flu, the common cold, neck and back pain, dysmenorrhea, headache, tooth pain, sprains, fractures, myositis, neuralgia, synovitis, arthritis, bursitis, burns, and various injuries. It is also used for symptomatic pain relief after surgical and dental procedures .
The extra strength formulation of acetylsalicylic acid is also indicated for the management migraine pain with photophobia (sensitivity to light) and phonophobia (sensitivity to sound).
Other indications
ASA is also indicated for various other purposes, due to its ability to inhibit platelet aggregation. These include:
Reducing the risk of cardiovascular death in suspected cases of myocardial infarction (MI) .
Reducing the risk of a first non-fatal myocardial infarction in patients, and for reducing the risk of morbidity and mortality in cases of unstable angina and in those who have had a prior myocardial infarction .
For reducing the risk of transient ischemic attacks (TIA) and to prevent atherothrombotic cerebral infarction (in conjunction with other treatments) .
For the prevention of thromboembolism after hip replacement surgery .
For decreasing platelet to platelet adhesion following carotid endarterectomy, aiding in the prevention of transient ischemic attacks (TIA) .
Used for patients undergoing hemodialysis with a silicone rubber arteriovenous cannula inserted to prevent thrombosis at the insertion site .
Important note regarding use of the extended-release formulation
In the setting of acute myocardial infarction, or before percutaneous interventions, the extended-release form of acetylsalicylic acid should not be used. Use immediate-release formulations in scenarios requiring rapid onset of action . The extended-release form is taken to decrease the incidence of mortality and myocardial infarction (MI) for individuals diagnosed with chronic coronary artery disease (CAD), including patients with previous myocardial infarction (MI) or unstable angina or with chronic stable angina. Additionally, the extended-release form is used to decrease the risk of death and recurrent episodes of stroke in patients with a history of stroke or TIA .

What are the applications of Application

Aspirin is an inhibitor of COX-1 (cylooxygenase) and NFκB

Pharmacokinetics

Effects on pain and fever
Acetylsalicylic acid disrupts the production of prostaglandins throughout the body by targeting cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) . Prostaglandins are potent, irritating substances that have been shown to cause headaches and pain upon injection into humans. Prostaglandins increase the sensitivity of pain receptors and substances such as histamine and bradykinin. Through the disruption of the production and prevention of release of prostaglandins in inflammation, this drug may stop their action at pain receptors, preventing symptoms of pain. Acetylsalicylic acid is considered an antipyretic agent because of its ability to interfere with the production of brain prostaglandin E1. Prostaglandin E1 is known to be an extremely powerful fever-inducing agent .
Effects on platelet aggregation
The inhibition of platelet aggregation by ASA occurs because of its interference with thromboxane A2 in platelets, caused by COX-1 inhibition. Thromboxane A2 is an important lipid responsible for platelet aggregation, which can lead to clot formation and future risk of heart attack or stroke .
A note on cancer prevention
ASA has been studied in recent years to determine its effect on the prevention of various malignancies . In general, acetylsalicylic acid is involved in the interference of various cancer signaling pathways, sometimes inducing or upregulating tumor suppressor genes . Results of various studies suggest that there are beneficial effects of long-term ASA use in the prevention of several types of cancer, including stomach, colorectal, pancreatic, and liver cancers . Research is ongoing.

Metabolism

Acetylsalicylic acid is hydrolyzed in the plasma to salicylic acid. Plasma concentrations of aspirin following after administration of the extended-release form are mostly undetectable 4-8 hours after ingestion of a single dose. Salicylic acid was measured at 24 hours following a single dose of extended-release acetylsalicylic acid .
Salicylate is mainly metabolized in the liver, although other tissues may also be involved in this process . The major metabolites of acetylsalicylic acid are salicylic acid, salicyluric acid, the ether or phenolic glucuronide and the ester or acyl glucuronide. A small portion is converted to gentisic acid and other hydroxybenzoic acids .