Aspirin


Generic Medicine Info
Indications and Dosage
Oral
Acute ischaemic stroke, Angina pectoris, Myocardial infarction
Adult: For primary prevention: Loading: 150-300 mg.

Oral
Fever, Mild to moderate pain
Adult: Initially, 300-900 mg, repeated 4-6 hourly according to clinical needs. Max: 4 g daily.

Oral
Rheumatic disorders
Adult: 4-8 g daily in divided doses for acute disorders. 5.4 g daily in divided doses for chronic conditions.

Oral
Prophylaxis of cardiovascular events in high-risk patients
Adult: Long term: 75-150 mg once daily. Short term: 150-300 mg daily.

Rectal
Fever, Mild to moderate pain
Adult: As suppository: 450-900 mg 4 hourly. Max: 3.6 g daily.
Renal Impairment
Severe: Contraindicated.
Hepatic Impairment
Severe: Contraindicated.
Administration
Should be taken with food.
Contraindications
Hypersensitivity to aspirin or other NSAIDs. Peptic ulcer, haemorrhagic disease, coagulation disorder (e.g. haemophilia, thrombocytopenia), gout. Severe hepatic and renal impairment. Children <16 years and recovering from viral infection. Pregnancy (doses >100 mg daily during 3rd trimester) and lactation. Concomitant use with other NSAIDs and methotrexate.
Special Precautions
Patient with dyspepsia or lesion of the GI mucosa, asthma or allergic disorders, anaemia, dehydration, menorrhagia, uncontrolled hypertension, G6PD deficiency, thyrotoxicosis. Patients undergoing surgical procedures. Moderate hepatic and renal impairment. Pregnancy.
Adverse Reactions
Significant: Salicylate sensitivity, tinnitus.
Blood and lymphatic system disorders: Anaemia, hypoprothrombinaemia, thrombocytopenia.
Gastrointestinal disorders: Dyspepsia, gastric irritation, nausea, vomiting.
Nervous system disorders: Dizziness, confusion.
Respiratory, thoracic and mediastinal disorders: Asthma, bronchospasm, dyspnea, rhinitis.
Skin and subcutaneous tissue disorders: Rash, urticaria.
Potentially Fatal: Paroxysmal bronchospasm and dyspnoea. Coma, CV collapse, resp failure, severe hypoglycaemia. Rarely, Reye’s syndrome. Hypersensitivity reactions (e.g. Stevens Johnson syndrome, angioedema), gastrointestinal bleeding and perforation.
Overdosage
Symptoms: Vomiting, dehydration, tinnitus, vertigo, deafness, sweating, warm extremities with bounding pulses, increased respiratory rate, hyperventilation, acid-base disturbance, haematemesis, hyperpyrexia, hypoglycaemia, hypokalaemia, thrombocytopenia, increased INR/PTR, intravascular coagulation, renal failure, pulmonary oedema, CNS effects (e.g. confusion, disorientation, coma, convulsion). Management: Administer activated charcoal if patient presents ingestion of >250 mg/kg within 1 hr. Perform urinary alkalinisation by administration of 1.26% Na bicarbonate then monitor urine pH. Correct metabolic acidosis with 8.4% Na bicarbonate IV. For severe poisoning (plasma conc: >700 mg/L), haemodialysis is the treatment of choice.
Drug Interactions
Increased risk of GI bleeding and ulceration with corticosteroids. Increased risk of bleeding with coumarin anticoagulants (e.g. heparin, warfarin, phenindione) and antiplatelet agents (e.g. clopidogrel, dipyridamole). May result in severe acidosis and increased CNS toxicity with carbonic anhydrase inhibitors (e.g. acetazolamide). Increases the hypoglycaemic effect of sulfonylureas. Reduces binding of phenytoin and valproate to serum albumin leading to increased free concentration of the drugs. Reduces the effect of uricosurics (e.g. probenecid, sulfinpyrazone). Impairs the renal excretion of lithium and digoxin.
Potentially Fatal: Increased risk of GI bleeding and ulceration with other NSAIDs. Increased risk of haematological toxicity of methotrexate.
Food Interaction
Increased risk of GI bleeding with alcohol. Reduced GI irritation with admin of food and large quantity of water or milk.
Lab Interference
Interferes with thyroid function, Gerhardt, VMA determination, 5-HIAA, and xylose tolerance tests. False negative result for glucose oxidase urinary glucose test; false positive in cupric sulfate method.
Action
Description: Aspirin is a salicylate that exhibits analgesic, anti-inflammatory, and antipyretic activities. It is a selective and irreversible inhibitor of cyclooxygenase-1 (COX-1) enzyme resulting in direct inhibition of the biosynthesis of prostaglandins and thromboxanes from arachidonic acid. Additionally, it also inhibits platelet aggregation.
Synonym: acetylsalicylic acid (ASA).
Onset: Platelet inhibition: Within 1 hr (nonenteric-coated); delayed (enteric-coated); 20 minutes (if chewed).
Duration: 4-6 hours (immediate-release); Platelet inhibition: Approx 10 days.
Pharmacokinetics:
Absorption: Rapidly absorbed from the gastrointestinal tract; less reliable (rectal); absorbed through the skin. Partially hydrolysed by esterases to salicylate during absorption in the GI tract. Bioavailability: 50-75% (immediate-release). Time to peak plasma concentration: Approx 1-2 hours (nonenteric-coated); 3-4 hours (enteric-coated); Approx 2 hours (extended-release cap).
Distribution: Widely and rapidly distributed into most body tissues and fluids. Crosses the placenta and enters breast milk. Volume of distribution: 170 mL/kg. Plasma protein binding: 80-90%.
Metabolism: Metabolised in the liver into salicyluric acid, salicyl phenolic glucuronide, salicylic acyl glucuronide, gentisic acid, and gentisuric acid. Undergoes first-pass metabolism.
Excretion: Via urine (75% as salicyluric acid, 10% as salicylic acid). Elimination half-life: 15-20 minutes.
Chemical Structure

Chemical Structure Image
Aspirin

Source: National Center for Biotechnology Information. PubChem Database. Aspirin, CID=2244, https://pubchem.ncbi.nlm.nih.gov/compound/Aspirin (accessed on Jan. 21, 2020)

Storage
Store below 25°C.
ATC Classification
N02BA01 - acetylsalicylic acid ; Belongs to the class of salicylic acids and derivatives agents. Used to relieve pain and fever.
A01AD05 - acetylsalicylic acid ; Belongs to the class of other agents for local oral treatment.
B01AC06 - acetylsalicylic acid ; Belongs to the class of platelet aggregation inhibitors excluding heparin. Used in the treatment of thrombosis.
References
Anon. Aspirin. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 05/07/2016.

Anon. Aspirin. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 05/07/2016.

Aspirin 325 mg Tablet (Allegiant Health). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 05/07/2016.

Buckingham R (ed). Aspirin. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 05/07/2016.

Joint Formulary Committee. Aspirin (Acetylsalicylic Acid). British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 05/07/2016.

Disclaimer: This information is independently developed by MIMS based on Aspirin from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2021 MIMS. All rights reserved. Powered by MIMS.com
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