Pharmacology
Central Nervous System
Which one of the following is a possible complication of aspirin therapy:
Answer:
Owing to an association with Reye’s syndrome, aspirin-containing preparations should not be given to children under 16 years, unless specifically indicated, e.g. for Kawasaki disease. Reye's syndrome is characterised by acute non inflammatory encephalopathy and fatty degenerative liver failure.Aspirin (Analgesic)
Pharmacology / Central Nervous System
Last Updated: 25th July 2020
Mechanism of Action
Aspirin is a non-steroidal anti-inflammatory drug (NSAID). Aspirin irreversibly inhibits cyclooxygenase (COX) enzymes and the resulting inhibition of prostaglandin synthesis results in analgesic, antipyretic and to a lesser extent anti-inflammatory actions. Low-dose aspirin also has an important antiplatelet activity through inhibition of thromboxane-A2 synthesis. The inhibition of prostaglandin synthesis in the gastric mucosa can result in gastrointestinal damage.
Indications
Aspirin is well absorbed orally and has a duration of action of about 4 hours. Aspirin is indicated for headache, transient musculoskeletal pain, dysmenorrhoea, and pyrexia. Aspirin is a first-line option for the management of migraine. In most circumstances where analgesia is required, other nonsteroidal anti-inflammatory drugs (such as ibuprofen) are preferred to aspirin, because they are better tolerated.
Contraindications
Aspirin (at analgesic doses) is contraindicated in:
- People with a history of true hypersensitivity to aspirin or salicylates (symptoms of hypersensitivity to aspirin or salicylates include bronchospasm, urticaria, angioedema, and vasomotor rhinitis)
- People with previous or active peptic ulceration
- People with haemophilia or another bleeding disorder
- Children younger than 16 years of age (risk of Reye's syndrome)
- People with gout, or a history of gout (aspirin increases the level of uric acid)
- People with severe cardiac failure (analgesic dose)
- People with severe hepatic impairment (increased risk of gastrointestinal bleeding)
- People with severe renal impairment (increased risk of deterioration of renal function and GI bleeding)
N.B. Owing to an association with Reye’s syndrome, aspirin-containing preparations should not be given to children under 16 years, unless specifically indicated, e.g. for Kawasaki disease.
Cautions
Aspirin (at analgesic doses) should be used with caution in:
- People who may be at high risk of increased bleeding — for example those receiving treatment with warfarin, NSAIDs, SSRIs, corticosteroids, or other drugs known to increase bleeding
- People with asthma or allergic disease (may precipitate bronchospasm)
- People with uncontrolled blood pressure
- People with thyrotoxicosis
- People with G6PD deficiency
- People with dehydration or renal impairment
- Elderly people (at higher risk of complications)
Side Effects
- Increased risk of bleeding
- Gastrointestinal adverse effects including irritation, bleeding, ulceration and dyspepsia
- Bronchospasm and asthma attacks in patients with asthma
- Skin reactions in hypersensitive patients
Overdose
The main features of salicylate poisoning are hyperventilation, tinnitus, deafness, vasodilatation, and sweating. Coma is uncommon but indicates very severe poisoning.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
