Pathology
Haematology
Question 70 of 180
Aspirin works as an antiplatelet drug through its ability to inhibit the synthesis of:
Answer:
Aspirin irreversibly inhibits cyclo-oxygenase impairing platelet synthesis of the prostaglandin thromboxane A2, preventing platelet aggregation.Antiplatelet and Anticoagulant Drugs
Pathology / Haematology / Coagulation Disorders
Last Updated: 25th June 2019
Antiplatelets
- Aspirin irreversibly inhibits cyclo-oxygenase impairing platelet synthesis of the prostaglandin thromboxane A2, preventing platelet aggregation.
- Dipyridamole inhibits both the reuptake of adenosine and phosphodiesterase, preventing the degradation of cAMP and thus blocking the platelet aggregation response to ADP.
- Clopidogrel inhibits the binding of ADP to its platelet receptor, preventing platelet aggregation.
- Abciximab, eptifibatide and tirofiban are GPIIb/IIIa inhibitors, inhibiting platelet aggregation by preventing the binding of fibrinogen, von Willebrand factor and other adhesive molecules.
Aspirin Antiplatelet Effect. (Image by Vtvu [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)])
Anticoagulants
- Unfractionated heparin potentiates the activity of antithrombin, which then inactivates thrombin, factor Xa and other proteases.
- Low molecular weight heparin (LMWH) preparations inhibit factor Xa directly. Inhibition of factor Xa prevents thrombin generation and thrombus development.
- Warfarin is a coumarin derivative that acts by inhibiting vitamin-K dependent clotting factors (factors VII, IX, X and II) as well as the anticoagulant proteins C and S.
- Apixaban, dabigatran, edoxaban and rivaroxaban are new anticoagulants with a novel mode of action:
- Apixaban, edoxaban and rivaroxaban are direct and reversible inhibitors of factor Xa.
- Dabigatran is a reversible inhibitor of free thrombin, fibrin-bound thrombin, and thrombin-induced platelet aggregation.
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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 |
