Flashcards in Katzung 12th ed - Chapter 34 - Anticoagulants (1) Deck (22):
In basic terms, describe the pharmacodynamics of Low Molecular Weight Heparin
LMWH binds to Antithrombin III, and enhances its inactivation of factor Xa.
In basic terms, describe the pharmacodynamics of Unfractionated Heparin.
Unfractionated Heparin binds to Antithrombin III, and enhances its activity 1000-fold. This activity is to inactivate factor Xa, factor IXa, and thrombin.
In basic terms, what is HIT?
Heparin Induced Thrombocytopaenia is a hypercoagulable state that can occur in patients treated with unfractionated heparin.
How common is HIT? Which patients are at higher risk of developing HIT and which are at lower risk?
HIT occurs in 1-4% of patients receiving UFH for a minimum of 7 days. It is more common in surgical patients, and less common in paediatric and pregnant patients.
Name a specific antidote to heparin, used in cases of excessive dosing. By which route is it given, and what is the dose?
Protamine sulphate. Give 1mg IV for every 100 units of heparin remaining in the patient.
What is the basic pharmocodynamics of rivaroxaban?
Rivaroxaban inhibits factor Xa.
What is the half-life of rivaroxaban?
Apart from rivaroxaban, name another drug that inhibits factor Xa?
What is the basic pharmacodynamics of dabigatran?
Dabigatran is a direct thrombin inhibitor.
Dabigatran: what if the patient has renal impairment?
Dose adjustment required: halve the dose.
Dabigatran puts patients at greater risk of ________ than warfarin does.
Warfarin: describe the basic pharmacodynamics.
Warfarin prevents the activation of vitamin K, which means that there is impaired synthesis of factors II (prothrombin), VII, IX, X (the vitamin-K-dependent clotting factors).
Warfarin: how much is protein-bound?
How is the INR calculated?
This is the patient's prothrombin time divided by the international mean prothrombin time (which is designated as 1).
Which drugs reduce the effect of warfarin by increasing its metabolism?
Barbiturates, Rifampicin. These drugs induce hepatic enzymes.
Cholestyramine binds warfarin in the intestine.
Which drugs (and conditions) reduce the effect of warfarin by interacting with or enhancing the synthesis of clotting factors?
Vitamin K, loop diuretics, hypothyroidism (decreased turnover of clotting factors), hereditary resistance to clotting factors.
Which drugs (and conditions) increase the effect of warfarin by interacting with or inhibiting the synthesis of clotting factors?
3rd gen cephalosporins (kill bacteria that produce vitamin K), Heparin, Hyperthyroidism (increased turnover of clotting factors), Aspirin in high doses (increased turnover of clotting factors)