Drugs acting in the bloodstream Flashcards
Regarding the anticoagulant effect of warfarin:
It is exerted directly on the blood
False
Warfarin prevents the reduction of vitamin K which is a co-factor in producing clotting factors II, VII, IX and X.
Regarding the anticoagulant effect of warfarin:
It is readily excreted in the urine
False
It is almost entirely metabolized in the liver by mixed function oxidases. The metabolites are excreted in the urine.
Regarding the anticoagulant effect of warfarin:
It is antagonized by salicylates
False
Regarding the anticoagulant effect of warfarin:
It is potentiated by phenylbutazone
True
Regarding the anticoagulant effect of warfarin:
It is potentiated by barbiturates
False
Regarding heparin:
It affects the coagulation pathway mainly by binding to ATIII (Antothrombin III); it has no direct antiplatelet activity
True. Its antiplatelet effects are mediated through its effects on fibrin.
Regarding heparin:
Haemorrhage and anaphylaxis are the commonest adverse drug reactions occurring after heparin therapy
False. Haemorrhage, hypotension and thrombocytopenia are the commonest adverse reactions.
Regarding heparin:
LMWH (Low Molecular Weight Heparin) is only partly reversed by protamine
True. Only anti-IIa activity is fully reversed, anti- Xa activity is partially reversed.
Regarding heparin:
For LMWH the APTT (Activated Partial Thromboplastin Time) ratio is a far more reliable indicator than INR (International Normalized Ratio)
False. Factor Xa assays are required to monitor effect of LMWHs, but owing to their safe profile, this is seldom performed.
Regarding heparin:
Heparin-induced thrombocytopenia is not dose-dependent
True. It can occur after the first dose of heparin.
Regarding warfarin, which of the following statements are true?
Protein C production is limited in patients on warfarin therapy
True. Protein C and S production are also inhibited by warfarin.
Regarding warfarin, which of the following statements are true?
It is 70% eliminated by renal filtration
False. It is almost entirely metabolized by the liver via inducible enzymes.
Regarding warfarin, which of the following statements are true?
It is highly protein bound
True. It is highly protein bound (99%) resulting in numerous drug interactions.
Regarding warfarin, which of the following statements are true?
Amiodarone, gliclazide or metronidazole can increase a patient’s INR
True. Gliclazide and amiodarone displace warfarin from albumin. Metronidazole is an enzyme inhibitor reducing warfarin metabolism.
Regarding warfarin, which of the following statements are true?
Unlike warfarin, heparin does not cause increased risk of stillbirths and abortions
False. Heparin causes an increased risk of fetal death and morbidity, but the incidence is less than warfarin.
Regarding low-molecular-weight heparin:
It has a similar effect on platelets as unfractionated heparin
False. LMWH interacts less with platelets than unfractionated heparin.
Regarding low-molecular-weight heparin:
It has a longer half-life than unfractionated heparin
True. The half-life of most low-molecular-weight heparins is 2–3 times longer than unfractionated heparin.
Regarding low-molecular-weight heparin:
Guidelines suggest at least 12 hours should elapse after dosing before attempting central neuraxial block
True. At least 12 h should elapse after dosing before attempting central neuraxial block, which is in accordance with the American Society of Regional Anesthesia (ASRA) guidelines; anti-Xa activity is about 50% of peak 12 h after dosing.
Regarding low-molecular-weight heparin:
It can be given 2-4 hours after uneventful spinal or epidural block
True. Low-molecular-weight heparin can be given 2-4 h after uneventful spinal or epidural block (see ASRA guidelines).
Regarding low-molecular-weight heparin:
It must be given before surgery to provide effective thromboprophylaxis
False. Postoperative dosing regimens have been shown to be equally effective in providing thromboprophylaxis.
With regard to coagulation studies:
You would expect a normal bleeding time in von Willebrand’s disease
False. You would expect a prolonged bleeding time due to the impaired platelet function.
With regard to coagulation studies:
The INR is the ratio of patient’s APPT to control using international reference preparation
False. It is the ratio of patient’s PT to control using international reference preparation.
With regard to coagulation studies:
Factor V abnormalities can result in a prolonged APTT
True. Factor V abnormalities can result in a prolonged APTT and PT.
With regard to coagulation studies:
Factor V abnormalities can result in a prolonged PT
True
With regard to coagulation studies:
Haemophilia is a cause of an elevated APTT
True. Both low factor VIII (haemophilia A) or IX (haemophilia B) would result in an elevated APTT.
