Aspirin

Oral
Mild to moderate pain
Adult: 300-900 mg 4-6 hourly as required. Max: 4,000 mg daily. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Oral
Fever
Adult: 300-900 mg 4-6 hourly as required. Max: 4,000 mg daily. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Oral
Myocardial infarction
Adult: Initial treatment: Loading dose: 150-300 mg. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Oral
Unstable angina
Adult: Initial treatment: Loading dose: 150-300 mg. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Oral
Transient ischaemic attack
Adult: Initial treatment: Loading dose: 150-300 mg. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Oral
Secondary prevention of thrombotic cerebrovascular disease
Adult: Long-term use: 75-150 mg once daily. Doses up to 300 mg daily may be necessary for some circumstances, particularly for short-term use. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Oral
Secondary prevention of cardiovascular disease
Adult: Long-term use: 75-150 mg once daily. Doses up to 300 mg daily may be necessary for some circumstances, particularly for short-term use. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Oral
Prevention of thrombotic complications following coronary artery bypass graft surgery
Adult: Long-term use: 75-150 mg once daily. Doses up to 300 mg daily may be necessary for some circumstances, particularly for short-term use. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Rectal
Mild to moderate pain
Adult: As supp: 450-900 mg 4 hourly. Max: 3,600 mg daily. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Rectal
Fever
Adult: As supp: 450-900 mg 4 hourly. Max: 3,600 mg daily. Treatment or dosage recommendations may vary among countries and individual products (refer to specific product guidelines).
Renal impairment: Severe: Contraindicated.
Hepatic impairment: Severe: Contraindicated.

Should be taken with food.

Hypersensitivity to aspirin, salicylates and other NSAIDs; history of asthma attacks, angioedema, urticaria, or rhinitis precipitated by aspirin or other NSAIDs. Nasal polyps associated with asthma; active or history of recurrent peptic ulceration and gastrointestinal haemorrhage; haemorrhagic diathesis, coagulation disorders (e.g. haemophilia, thrombocytopenia), severe cardiac failure, gout. Severe renal and hepatic impairment. Children <16 years and/or those who have or are recovering from chickenpox or flu-like symptoms. Pregnancy (doses >100 mg daily during 3rd trimester) and lactation (during long-term use and/or high doses). Concomitant use with methotrexate ≥15 mg weekly.

Patient with allergic disease, asthma, chronic respiratory disease, anaemia, less severe cardiac failure, SLE, connective tissue disorders, thyrotoxicosis, hypertension, G6PD deficiency, risk factors for peptic ulcer disease (e.g. alcoholism, smoking). Patients undergoing surgical procedures, including tooth extraction. Not recommended for use during menorrhagia. Avoid use for 6 weeks following varicella vaccination. May mask signs and symptoms of infection. Concomitant use with anticoagulants (e.g. warfarin), thrombolytic, other antiplatelet agents, SSRIs, and oral corticosteroids. Avoid concomitant use with other NSAIDs. Dehydrated and debilitated patients. Mild to moderate renal and hepatic impairment. Elderly. Pregnancy (1st-2nd trimester). Monitoring Parameters Obtain CBC, Fe studies, ferritin, stools for occult blood, and liver and renal function tests during prolonged therapy. Monitor for signs and symptoms of hypersensitivity reactions and bleeding.

Significant: Bronchospasm, asthma attacks, hypersensitivity reactions, prolonged bleeding time; reduced uric acid excretion (low dose use); haemolytic anaemia (in patients with G6PD deficiency), medication overuse headache (long-term use), salicylism (repeated use of large doses). Blood and lymphatic system disorders: Rarely, thrombocytopenia, agranulocytosis, aplastic anaemia. Ear and labyrinth disorders: Reduced hearing ability, tinnitus, vertigo. Gastrointestinal disorders: Dyspepsia, nausea, vomiting, diarrhoea, mild stomach pain, heartburn. Hepatobiliary disorders: Hepatic insufficiency, hepatitis. Investigations: Increased transaminases. Nervous system disorders: Headache. Renal and urinary disorders: Impaired renal function, Na and fluid retention, urate kidney stones, haematuria. Reproductive system and breast disorders: Rarely, menorrhagia. Respiratory, thoracic and mediastinal disorders: Rhinitis, dyspnoea. Skin and subcutaneous tissue disorders: Urticaria.
Potentially Fatal: Gastrointestinal bleeding, ulceration, and perforation. Rarely, Reye's syndrome, serious skin reactions (e.g. Stevens-Johnson syndrome, erythema multiforme, toxic epidermal necrolysis).

Symptoms: Vomiting, nausea, abdominal pain, dehydration, tinnitus, headache, vertigo, deafness, hearing disorders, sweating, warm extremities with bounding pulses, hyperventilation resulting in respiratory alkalosis, metabolic acidosis with normal or high arterial pH (normal or reduced hydrogen ion concentration), haematemesis, hyperpyrexia, hypoglycaemia, hypokalaemia, thrombocytopenia, increased INR, intravascular coagulation, renal failure, non-cardiac pulmonary oedema, hyperthermia, restlessness, hallucinations, confusion, disorientation, convulsions, CV collapse, respiratory arrest, coma. Management: Symptomatic and supportive treatment. Induce vomiting in the event of moderate intoxication; if unsuccessful, consider performing gastric lavage in adults and children who ingested >500 mg/kg salicylate within 1 hour of presentation, then administer activated charcoal for ingestion of >250 mg/kg salicylate. Perform urinary alkalinisation by administration of 1.26% Na bicarbonate and monitor urine pH levels. Maintain fluid and electrolyte balance. Correct metabolic acidosis with 8.4% Na bicarbonate IV. For severe poisoning and plasma concentrations >700 mg/L or lower concentrations associated with severe clinical or metabolic features, haemodialysis is the treatment of choice.

Increased risk of bleeding with other antiplatelet agents (e.g. clopidogrel, dipyridamole), anticoagulants (e.g. heparin, warfarin), and thrombolytics. Increased risk of gastrointestinal bleeding or ulceration with other NSAIDs, SSRIs (e.g. sertraline, paroxetine), and corticosteroids. Reverses the effect of uricosuric agents (e.g. probenecid, sulfinpyrazone). May increase the effects of antidiabetics (e.g. sulfonylureas, insulins) and thiopental. Impairs the renal excretion of lithium and digoxin, thus increasing the plasma concentrations of the drugs. Increased excretion with antacids. May decrease the effects of diuretics (e.g. spironolactone, furosemide) and antihypertensive agents (e.g. ACE inhibitors, β-blockers). May result in severe acidosis and increased CNS toxicity with carbonic anhydrase inhibitors (e.g. acetazolamide). May increase the nephrotoxic effect of ciclosporin and tacrolimus. Increases the plasma concentration of zafirlukast. Reduces the binding of phenytoin and valproic acid to serum albumin, resulting in increased free concentration of the drugs. Concomitant use with metamizole or ibuprofen may reduce the cardioprotective effect of aspirin. May enhance the adverse or toxic effect of varicella virus-containing vaccines (particularly the risk for Reye's syndrome), sulfonamides, and vancomycin (particularly ototoxicity). Increased rate of absorption with metoclopramide and domperidone.
Potentially Fatal: Enhances the haematological toxicity of methotrexate, particularly when used at doses ≥15 mg weekly.

Increased risk of gastrointestinal bleeding with alcohol. Decreased rate but not the extent of absorption with food.

May lead to false-negative results for glucose oxidase urinary glucose tests. May lead to false-positive results of aldosterone/renin ratio (ARR) and when using cupric sulfate method. Aspirin interferes with Gerhardt test, vanillylmandelic acid (VMA) determination, 5-hydroxyindoleacetic acid, xylose tolerance test, and thyroid function tests (T₃ and T₄).

Aspirin is a salicylate that exhibits analgesic, anti-inflammatory, and antipyretic activities. It is an irreversible inhibitor of cyclooxygenase-1 and 2 (COX-1 and 2) enzymes, resulting in direct inhibition of the biosynthesis of prostaglandins. It inhibits platelet aggregation via acetylation of platelet cyclooxygenase, thus irreversibly preventing the formation of platelet aggregating factor thromboxane A₂. Synonym: acetylsalicylic acid (ASA).
Onset: Platelet inhibition: <1 hour (nonenteric-coated tab); 3-4 hours (enteric-coated tab); 20 minutes (when chewing nonenteric- or enteric-coated tab).
Duration: Oral: 4-6 hours. Platelet inhibition: Approx 10 days.
Absorption: Rapidly and well absorbed from the gastrointestinal tract (oral). Food reduces the rate but not the extent of absorption. Bioavailability: 50-75%. Time to peak plasma concentration: Nonenteric-coated tab: Approx 1-2 hours (20 minutes when chewed); Enteric-coated tab: 3-4 hours (2 hours when chewed).
Distribution: Widely and readily distributed into most body tissues and fluids. Crosses the placenta and enters breast milk. Volume of distribution: 10 L. Plasma protein binding: Aspirin: 33%. Salicylate: 90-95% (<100 mcg/mL concentration); 70-85% (100-400 mcg/mL concentration); 25-60% (>400 mcg/mL concentration).
Metabolism: Partially hydrolysed by esterases in the gastrointestinal mucosa to salicylate (active), which is then conjugated in the liver into salicyluric acid, salicyl phenolic glucuronide, salicylic acyl glucuronide, gentisic acid, and gentisuric acid.
Excretion: Via urine (75% as salicyluric acid, 10% as salicylic acid, 10% as phenolic glucuronide, 5% as acyl glucuronide). Elimination half-life: Aspirin: 15-20 minutes (plasma concentration). Salicylate: Approx 2-3 hours (325 mg dose); 15-30 hours (high doses).

Oral: Tab/cap/caplets: Store below 30°C. Storage recommendations may vary among countries or individual products. Refer to specific product guidelines. Rectal: Rectal supp: Store between 2-15°C. Do not freeze. Storage recommendations may vary among countries or individual products. Refer to specific product guidelines.

Anticoagulants, Antiplatelets & Fibrinolytics (Thrombolytics) / Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)