Drugs that act on the blood

Question 1

Fibrinolytic drugs

Answer 1

dissolve a pre-existing clot or thrombus

used when patients have had an acute myocardial infarction.

acute/emergency drug - v fast acting. Via IV

danger of haemorrage / fragments of clot splitting off.

anteplase digests clots in coronory arteries. converts plasminogen to plasmin.

streptokinase - used to dissolve blood clots. Breaks down clots in coronary vessels (heart and lungs).
Extracted from bacteria

Question 2

HEPARIN (parin = heparin!!)

Answer 2

Protein. Natural anticoagulant. Present in the liver, kidney, lungs, mast cells.

Heparin - unfractionated

Low MW Heparins - enoxapain, dalteparin, tinzaparin (Parin= heparin!!) more predictable than heparin. Can be given post surgery to reduce the risk of thrombosis. Given in pregnancy

Heparin activates antithrombin III

Factor Xa deactivates them.

Problems - poorly absorbed orally. Given by IV. Risk of haemorrhage - in severe cases protamine sulphate stops it working.

Question 3

WARFARIN

Answer 3

related to vitamin K

antagonises vit K role in clotting.

Factors II (prothrombin) VII and IX

SLow onset of 3 days

risk of haemorrhage - in severe cases give vitamin K

avoid in early and late pregnancy

Drug interactions - carbamazepine - increases warfarin metabolism

Cemetidine - reduces metabolism of warfarin.

Question 4

Future anti-coagulant drugs

Answer 4

Riraroxaban (xarelto) given orally. Licenced for knee replacements. Inhibits thrombin (Factor Xa)

Diblgartan - direct thrombin inhibitor. Prodrug. Converted by enzymes in the GI tract into dabigatran,a thrombin inhibitor.

Question 5

Anti-platelet drugs

Answer 5

Damage to blood vessel wall exposes proteins. Platelets adhere to the wall. Helped by Viii to form a clot and release thromboxane.

1. Increaces the ability of cells to stick together.
2. Makes the blood vessel smaller. - vaso constriction.

Prostacyclin - also produced. Prevents too much clotting.

Targets - receptors on platelets - reduce

Asprin - irreversibly blocks platelet COX enzyme. Prevents thromboxine synthesis. Lasts 7-10 days until new ones are made. Low doses used.

CLOPIDIGREL - inhibits glycoprotein 11a/11b. Receptor on platelets.
Blocks glycoprotein pathway.
When fibrin is formed the platelets cannot stick together.

pro drug - activated by liver.

Dipinidramole. PDE Enzyme. Prevents breakdown of AMP in platelets.