Aspirin
Aspirin is a non-steroidal anti-inflammatory drug. Now when you fall down or sustain any sort of injury, there will be release of various inflammatory mediators especially prostaglandins at the site of inflammation and these are responsible for carrying out the inflammatory reactions such as burning sensation. Now have you ever heard of this enzyme called as COX which is cyclooxygenase. This is the enzyme which is responsible for the production of prostaglandins from arachidonic acid. Now aspirin effectively inhibits cyclooxygenase enzyme, by doing so they decrease prostaglandin synthesis and thereby decreasing inflammation. The cyclooxygenase enzyme has two isoforms cyclooxygenase 1 and cyclooxygenase 2 which is responsible for inflammatory reactions. Now aspirin being a non-selective COX inhibitor, inhibits both the isoforms. The COX 1 isoform is responsible for physiological activities whereas COX 2 isoform is responsible for inflammatory reactions.
Oral Rroute
Aspirin is usually given by oral route. It is absorbed from the gastric mucosa as well as intestinal mucosa. Aspirin is absorbed only in the unionized form in which it will be diffusible. When aspirin
enters the gastric mucosal cells it can get converted into ionized form when it becomes non diffusible. When aspirin becomes non diffusible, that is in the ionized form it cannot leave the gastric mucosal cell and so it gets trapped inside the gastric mucosal cell leading to ion trapping. This increases the gastric mucosal damage. In addition to that aspirin also blocks a physiologically important enzyme which is COX 1 which is responsible for maintenance of gastric mucosal integrity and by blocking the COX 1 enzyme aspirin increases the risk of mucosal damage. Aspirin is metabolized byliver and excreted by kidneys.
Bound to Plasma Proteins
About 80 percent of aspirin in the plasma is bound to plasma proteins and it displaces drugs such as warfarin, naproxen and many other drugs from plasma proteins. By doing so they increase the plasma levels of these drugs and increase the toxicity associated with these drugs.
Actions
- Analgesic
- Antipyretic
- Antiinflammatory
- Inhibits Platelet Aggregation
- Hyperventilation, Resoiratory Failure and Death
- Acid-base Imbalance
- Increases Cardiac Output
- Gastric Mucosal Damage and Ulceratio
The pharmacological actions of aspirin. In lower doses, aspirin acts as an analgesic drug and that's by desensitizing the peripheral pain receptors to the action of prostaglandins and by doing so pain perception is reduced. Aspirin also act as antipyretic drug by resetting the hypothalamic thermostat and by doing so it increases sweating and cutaneous vasodilatation and various other mechanisms to increase heat loss from the body. At higher doses aspirin acts as a very good anti-inflammatory drug and that's by decreasing prostaglandin synthesis by blocking the cyclooxygenase enzyme which i've already explained before. Aspirin also inhibits platelet aggregation. Now this effect is well observed in lower doses of aspirin. It does that by decreasing thromboxane A2 synthesis which is also a product produced by the cyclooxygenase enzyme. Aspirin causes hyperventilation in higher doses leading to acidotic breathing and in very toxic doses aspirin causes respiratory failure and even death. Aspirin is more often associated with various acid-base imbalance disorders such as compensated respiratory alkalosis in higher doses and uncompensated metabolic acidosis in very toxic doses due to renal failure. Aspirin can also increase the cardiac output to meet for the increased peripheral oxygen demand produced by aspirin. As I've explained earlier aspirin can cause gastric mucosal damage, ulceration and gastric bleeding.
Uses of Aspirin
- analgesic and antipyretic
- Acute Rheumatic Fever
- Rheumatoid Arthritis
- Post Myocardial Infarction and Post Stroke
- Patent Ductus Arteriosus
Uses of aspirin. Aspirin can be used as analgesic as well as antipyretic in low doses but however for this purpose better alternatives such as paracetamol can be used which is associated with lesser side-effects. Aspirin is very commonly used in the treatment of acute rheumatic fever where it helps in symptomatic control of the disease it is also used for rheumatoid arthritis but for this purpose better alternatives are available. It is most commonly used in post myocardial infarction and post stroke patients to prevent recurrence of the disease. Aspirin is also used in patent ductus arteriosus in which case it is used to bring about closure of the patent ductus arteriosus without the need for surgery.
toxicity
Let's see about the toxicity of aspirin. Aspirin in lower doses are usually associated with milder side effects such as mild GI distress, epigastric pain, nausea, vomiting, etc., However when higher doses of aspirin are given, this can lead to a syndrome known as salicylism in which there be various clinical manifestations ranging from hyperventilation and acidotic breathing, reversible hearing loss and vision loss, tinnitus, vertigo, nausea, vomiting and so many other features. Hypersensitivity and associated anaphylactic reactions is rare in the case of aspirin and there is this thing called as acute salicylate poisoning when you give over doses of aspirin at a time. There will be severe manifestations such as respiratory depression, coma and uncompensated metabolic acidosis due to the accumulation of various metabolic acids in the body and can lead to death of the patient. The various.
Contraindications
Contraindications for aspirin. In children, especially who are infected with influenza, chickenpox and various other viral infections, it's better to avoid aspirin as it can cause Reye's syndrome in these patients. This is actually manifested by encephalopathy as well as liver damage. It should be avoided in patients with heart diseases because this can increase the workload of the heart and can lead to precipitation of congestive cardiac failure. It can cause gastric ulcers as I've already told you, so it should be prevented in patients with gastric ulcers. Most importantly it should be avoided in pregnant women, because it can cause prolonged labor and it can also cross the placental barrier to reach the fetus and very importantly it should be prevented in persons with bleeding disorders because this increases the risk of bleeding.