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Blood Pharmacology

Blood Pharmacology. Peer Support 2014. Case 1. Mrs A recently seen one of your colleagues complaining of fatigue. Her blood test results are now back and she has came to your clinic for a follow up appointment. You diagnose her as being anaemic . What are the 3 main classes of anaemia ?

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Blood Pharmacology

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  1. Blood Pharmacology Peer Support 2014

  2. Case 1 Mrs A recently seen one of your colleagues complaining of fatigue. Her blood test results are now back and she has came to your clinic for a follow up appointment. You diagnose her as being anaemic. What are the 3 main classes of anaemia? • Microcytic, Hypochromic • Normocytic, Normochromic • Macrocytic, Normochromic

  3. Case continued… • Mrs A blood results are as follows: - Hb 9.9 (11.5-16g/dL) - MCV 71 (76-96fL) - WCC 7.8 (4-11x10^9/L) - Plts 220 (150-400x10^9/L) Which class of anaemia is Mrs A suffering from? Microcytic, hypochromic Give 3 causes of this type of anaemia? Iron deficiency Thalasseamias Anaemia of chronic disease

  4. 2 Causes of Normocytic, Normochromic anaemia? • Acute haemorrhage • Haemolyticanaemia • Bone marrow failure • Pregnancy 2 causes of Macrocytic, Normochromic anaemia? • B12 deficiency • Folate deficiency • Hypothyroidism

  5. Further blood tests are ordered for Mrs A. She has low ferritin levels, therefore her symptoms are likely due to poor iron intake. • What medication would be suitable for Mrs A to start taking? • Ferrous Sulphate(200mg TDS) Ferrous sulphate is often poorly tolerated by patients. What are possible side effects? • Constipation • Black Stools • GI upset – dyspepsia, nausea

  6. Case 2 • Mrs B is an 84 year old gentleman who has been referred to the emergency department as his blood results are abnormal. He takes warfarin for atrial fibrilation. • What blood result is likely to be abnormal? • INR What is INR? • A standardised version of the prothrombin time INR should usually be 1. What is the usual therapeutic range? - 2-3

  7. Case 2 continued… Mr B’s INR is 6. What treatment options do you have? • Conservative: Stop warfarin and wait for his INR to fall before restarting warfarin • Give Vitamin K If Mr B was actively bleeding, what action should be taken? - FFP (Fresh frozen plasma) This will reverse the effect of warfarin immediately

  8. Warfarin – Mechanism of Action • EXTRINSIC Pathway • What enzyme does warfarin inhibit? - Vitamin K Epoxide Reductase (in the liver) – therefore lowering the level of reduced vitamin K. (Vitamin K required as a cofactor for the carboxylation of glutamate residues in some coagulation factors) Which coagulation factors does this have an effect upon? • II, VII, IX and X How long does it usually take for warfarin to have a therapeutic effect? Approx 72 hrs Why is this? - This is how long it takes for the clotting factors already active in the blood to be metabolised and depleted.

  9. Give 3 examples of situations when warfarin must not be given? • Haemmorhagic Stroke • 48 hours post partum • During pregnancy • Malignant hypertension Give 2 drugs/substances that may interact with warfarin, causing an INCREASE in INR? • Erythromycin • Acute alcohol intoxication Give 2 that can cause warfarin to have a reduced therapeutic effect? • Barbituates • Phenytoin

  10. Side effects of warfarin, besides bleeding? • Skin Necrosis • Pancreatitis • Alopecia • Hepatitis • Jaundice • NVD Warfarin vs Heparin - PeTPiTT – Try to remember which pathway and the relevant lab tests

  11. Heparin and LMWH • Advantages of LMWH over Heparin? • Longer plasma half life • Better bioavailability • More predictable dose response Give an example of a LMWH drug? • Enoxaparin Mechanism of action of heparin/LMWH? • Bind to and activiateAntithrombin III • Antithrombin III inactivates Thrombin • Factor Xa is also inhibited

  12. If a patients is accidently given a heparin overdose – what can be given to reverse the effect? • Protamine Sulphate– a basic peptide, binds with heparin and prevents its function 2 Side effects of longterm heparin use? • Thrombocytopenia (HIT 2 types) • Alopecia • Osteoperosis

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