Aspirin

Aspirin

80mg Tablet

100mg Tablet

300mg Tablet

500mg Tablet

DRUG CATEGORY:

Analgesic; Anti-inflammatory agent; Anticoagulant agent

PHARMACOLOGY:

General Pharmacology:

The action o aspirin is vastly due to its capacity to inhibit prostaglandin biosynthesis. It does this by irreversibly blocking the enzyme cyclooxygenase (prostaglandin synthase), which catalyzes the conversion of arachidonic acid to endoperoxide compounds. At appropriate doses, the drug decreases the formation of both the prostaglandins and thomboxane A₂ but not the leukotrienes. Most of an anti-inflammatory dose of aspirin is rapidly deacetylated to form salicylate as the active metabolite. Salicylate reversibly inhibits prostaglandin synthesis.

Analgesic Action:

Aspirin acts peripherally through its effects on inflammation but probably also inhibit pain stimuli at a subcortical site.

Antipyretic Action:

Aspirin alleviates fever by causing blood vessels in the skin to open, allowing heat to leave the body more rapidly.

Platelet Action:

Aspirin inhibit platelet aggregation secondary to inhibition of thromboxane synthesis. Because its action is irreversible, aspirin inhibits platelet aggregation for up to 8 days until new platelets are formed.

PHARMACOKINETICS:

The salicylates are rapidly absorbed from the stomach and upper small intestines, yielding a peak plasma salicylate level within 1 to 2 hours. The acid medium in the stomach keeps a large fraction of the salicylate in the nonionized from, promoting absorption. However, when high concentration of salicylate enter the mucosal cell, the drug may damage the mucosal barrier. If the gastric pH is raised by a suitable buffer to 3.5 or higher, gastric irritation is minimized.

Aspirin is absorbed as such and is hydrolyzed to acetic acid and salicylate by esterases in tissue and blood. Salicylate is bound to albumin, but, as the serum concentration of salicylate increases, a greater fraction remains unbound and available to tissues. Ingested salicylate and that generated by the hydrolysis converted to water-soluble conjugates that are rapidly cleared by the kidney. When this pathway becomes saturated, a small increase in plasma levels. Alkalinization of the urine increases the rate of excretion of free salicylate. When aspirin is used in low doses (600mg), elimination is in accordance with first order kinetics and the serum half-life is 3 to 5 hours. With higher dosage, zero-kinetics prevail; at anti-inflammatory dosage (≥4 g/d), the half-life increase to 15 hours or more. This effect occurs in about a week and is related to saturation of hepatic enzymes that catalyze the formation of salicylate metabolites, salicylphenylglucuronide and salicyluric acid.

INDICATIONS:

Quick relief of mild to moderate pain such as headache, neuralgia and periodic pains. It reduces fever discomfort in colds and flu. It is also use for prophylaxis of patients who suffer from thromboembolic disorders in preventing myocardial infarction and transient ischemic attacks. Aspirin in a long term effect may reduce cataract formation according to some studies.

DOSAGE AND ADMINISTRATION:

Adult: 100mg tablet once a day for prophylaxis of thromboembolic disorders. Headache, rheumatism, muscular pains, toothache, neuralgia, periodic pains, fever and discomfort in colds and flu: 1 to 2 tablets. Repeat 3 to 4 hours if necessary.

Children: 5 yrs old 1 tab; 3 to 5 ½ tab. Repeat if necessary but not greater than 3 times daily. Caution when given to children age 16 and under, Reye's syndrome may can acquire.

Take aspirin immediately after meals, because it can cause upset stomach or bleeding. If you forget to take a dose of Aspirin, take it as soon as you remember. If it is almost time for your next dose, skip the forgotten dose and continue with your regular schedule. Do not take a double dose.

CONTRAINDICATIONS:

Aspirin is contraindicated to individuals who have history of salicylate-induced asthma. It is also contraindicated to patients who are suffering from active peptic ulcers, hemorrhagic diathesis, severe renal or cardiac failure and those taking methotrexate at doses of ≥15mg/wk. Aspirin should not be used by patients who are hypersensitive to this medication.

ADVERSE DRUG REACTIONS:

Most Common: Nausea, upset stomach, heartburn, loss of appetite, and loss of small amounts of blood in the stool.

Rare: Hives, rashes, liver damage, fever, thirst, and difficulties with vision. Aspirin may develop dizziness, hearing loss, or ringing or buzzing in your ears. Aspirin may contribute to the formation of stomach ulcers and bleeding. People who are allergic to Aspirin and those with a history of nasal polyps, asthma, or rhinitis may experience breathing difficulty and a stuffed nose.

DRUG INTERACTIONS:

1. Patients who are taking other anticoagulant drugs (such as clopidogrel, warfarin) should avoid Aspirin. The effect of anticoagulant will be augmented.
2. Do take aspirin concomitantly with adrenal corticosteroids, phenylbutazone, or alcoholic beverages.
3. Aspirin may increase blood levels of Methotrexate and of Valproic Acid when taking with either of these drugs, leading to increased chances of drug toxicity. Aspirin and Nitroglycerin tablets may lead to an unexpected drop in blood pressure.
4. Avoid taking Aspirin with a NSAID. There is no benefit to the combination, and the chance o side effects, especially stomach irritation, is vastly increased.
5. Large Aspirin doses (2000mg per day or more) can lower blood sugar. This can be a problem in diabetics who take insulin or oral antidiabetes drugs to control their condition.
6. Do not take aspirin with carbonated drinks or acidic beverages. Doing so may lead to increased stomach acidity leading to severe stomach irritation or bleeding.
7. Milk or other basic food can slower Aspirin absorption, because aspirin can be absorbed faster in an acidic environment. When aspirin is taken with these food ionization will occur and aspirin will not be absorbed.