Pharmacology
Renal, Blood and Haematological Pharmacology
Blood and kidney drugs for MBBS and NEET-PG: heparin, warfarin, antiplatelets, thrombolytics, haematinics and diuretics, mapped to NMC codes.
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Renal, Blood and Haematological Pharmacology
Blood and kidney drugs for MBBS and NEET-PG: heparin, warfarin, antiplatelets, thrombolytics, haematinics and diuretics, mapped to NMC codes.
This chapter covers the drugs acting on the kidney and the blood, including diuretics, anticoagulants, antiplatelet agents, thrombolytics and the haematinics used in anaemia. It links their mechanisms to the therapeutics of oedema, thromboembolism, bleeding disorders and nutritional deficiency.
High-yield: Renal, Blood and Haematological Pharmacology
- Heparin acts immediately by potentiating antithrombin and is monitored by the activated partial thromboplastin time; protamine reverses it.
- Low-molecular-weight heparin such as enoxaparin has a predictable response and usually needs no monitoring.
- Warfarin inhibits vitamin K-dependent clotting factors, has a delayed onset, is monitored by the INR and is teratogenic.
- Warfarin overdose or bleeding is managed with vitamin K and, if severe, prothrombin complex concentrate or fresh frozen plasma.
- Many drugs potentiate warfarin by enzyme inhibition, so bleeding risk rises when it is combined with metronidazole or amiodarone.
- Aspirin and clopidogrel are antiplatelet agents; clopidogrel blocks the ADP receptor on platelets.
- Streptokinase and alteplase are thrombolytics used in acute myocardial infarction; the main risk is haemorrhage.
- Direct oral anticoagulants such as dabigatran and rivaroxaban need no routine monitoring and have specific reversal agents.
- Oral iron is first-line for iron deficiency anaemia and commonly causes constipation and dark stools.
- Vitamin B12 deficiency causes megaloblastic anaemia with neurological features, treated with intramuscular hydroxocobalamin.
- Folic acid supplementation before and during early pregnancy reduces the risk of neural tube defects.
- Erythropoietin treats the anaemia of chronic kidney disease but raises the risk of hypertension and thrombosis.
- Loop diuretics act on the thick ascending limb and are the most powerful diuretics, useful in pulmonary oedema.
- Mannitol is an osmotic diuretic used to reduce raised intracranial and intraocular pressure.
Anticoagulants and haematinics
- **Heparin:** Immediate action; monitored by APTT; reversed by protamine; safe in pregnancy.
- **Warfarin:** Delayed onset; monitored by INR; reversed by vitamin K; teratogenic.
- **Iron deficiency:** Oral ferrous salts first-line; constipation and dark stools common.
- **Megaloblastic anaemia:** Vitamin B12 or folate; give B12 with neurological signs before folate alone.
NMC competencies in this chapter
- **PH1.24:** Drugs acting on blood: anticoagulants, antiplatelets and thrombolytics
- **PH1.25:** Haematinics and drugs for anaemia
- **PH1.35:** Diuretics and drugs acting on the kidney
Frequently Asked Questions
How do heparin and warfarin differ in onset?
Heparin works immediately by activating antithrombin, while warfarin takes days because it must first deplete existing vitamin K-dependent clotting factors.
How is warfarin monitored and reversed?
It is monitored by the INR, and bleeding is reversed with vitamin K, with prothrombin complex concentrate or fresh frozen plasma for severe cases.
Why is warfarin avoided in pregnancy?
It crosses the placenta and is teratogenic, so heparin, which does not cross the placenta, is preferred when anticoagulation is needed in pregnancy.
When is vitamin B12 given before folate?
In megaloblastic anaemia with neurological signs, giving folate alone can worsen the neuropathy, so B12 must be corrected first or given together.
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