ELM 8.1 Flashcards
In this question there are three correct answers that each score 1/3 of the marks. You can select up to three answers.
Types of acute coronary syndrome (ACS) include:
[mark all correct answers]
a.
NSTEMI
b. Stable angina c. STEMI d. Unstable angina
a, c, d
All of these conditions involve severe chest pain radiating to the left side of the body. The pain is caused by cardiac ischaemia from blockage of a coronary artery. ACS includes NSTEMI, STEMI and unstable angina. These three conditions are not relieved by rest, unlike stable angina.
The key feature that distinguishes unstable angina and NSTEMI is:
a. presence of blood markers b. ST inversion c. ST depression d. ST elevation
a
Unstable angina is the least serious of the ACS and patients will not have the cardiac proteins in the blood that are released during the muscle damage seen in STEMI and NSTEMI.
In this question there are three correct answers that each score 1/3 of the marks. You can select up to three answers.
Unfractionated heparins bind directly to:
[mark all correct answers]
a.
anti-thrombin III
b. factor IIa c. factor Xa d. thrombin
a, b, d
Heparin binds to antithrombin III (ATIII) and increases its affinity for factor Xa and for thrombin (factor IIa). Xa is a lot more sensitive to ATIII than is thrombin and to inhibit thrombin heparin must also bind directly to thrombin. Low molecular weight heparins are not long enough to bridge between ATIII and thrombin and so only act via inhibition of Xa.
Which of the following compounds is made by fractionating heparin?
a. Enoxaparin b. Fondaparinux c. Anti-thrombin III d. Protamine
a
Enoxaparin is a low molecular weight heparin made by fractionating heparin. Fondaparinux is a similar compound, but it is synthetic. Antithrombin III is part of the clotting cascade control mechanism. Protamine is an antidote to heparin.
In this type of question, two statements are given (X and Y). You must decide if each of these statements is true and, if both are true, whether X is the reason for Y.
Statement X: Warfarin is a vitamin K reductase inhibitor
Statement Y: Warfarin blocks the production of active clotting factors
a. Statement X is false; statement Y is false b. Statement X is false; statement Y is true c. Statement X is true; statement Y is false d. Statement X is true; statement Y is true AND X is NOT the reason for Y e. Statement X is true; statement Y is true AND X IS the reason for Y
e
Vitamin K is needed for the production of active clotting factors. Warfarin is an analogue of vitamin K and inhibits the enzyme vitamin K reductase, which is needed to recycle vitamin K for use in clotting factor activation.
In this question, choose the one most appropriate response from the options
Warfarin is an analogue of which naturally occurring toxin?
a. anti-thrombin III b. dicoumarol c. haemolysin d. vitamin K
b
Warfarin was developed based on the structure of dicumarol, a toxin produced when fungi breakdown sweet clover. It is also an analogue of vitamin K, so it’s important to notice the word “toxin” in the question.
When warfarin is used to prevent thrombosis, potential problems include:
[mark all correct answers]
a.
increased risk of haemorrhage
b. interactions with other drugs c. lack of oral effectiveness d. teratogenic effects
a, b, d
Warfarin interacts with many other drugs and even components of the patient’s diet. It can be taken orally (unlike heparin) and it is a teratogen. Like all drugs we’ve met in this part of the course, it can increase the risk of haemorrhage.
A drug that acts as a substrate for thrombin is:
a. Bivalirudin b. Dabigatran c. Hirudin d. Rivaroxaban
a
Bivalirudin is a synthetic hirudin analogue that is a competitive substrate at thrombin. Dabigatran and hirudin are competitive inhibitors of thrombin. Rivaroxaban acts at Factor Xa, not thrombin.
Which of the following are orally active anticoagulants?
[mark all correct answers]
a.
Dabigatran
b. Hirudin c. Rivaroxaban d. Warfarin
a, c, d
Hirudin is a peptide and in general, peptide drugs cannot be administered orally because they are broken down in the GI tract.
Which of the following is a prodrug?
a. Clopidogrel b. Dipyridamole c. Ticagrelor d. Warfarin
a
Clopidogrel is a prodrug and needs to be metabolised by CYP2C19 to become active. About 30% of the population have a low functioning allele of this enzyme and so do not respond as well to clopidogrel.
What is the signalling molecule produced by the vascular endothelium that inhibits platelet activation?
a. ADP b. Endothelin c. Prostacyclin d. Thromboxane A2
c
Thromboxane A2 and ADP are signals produced by platelets that INCREASE activation and aggregation. Endothelin is a peptide produced by the endthelium that constricts blood vessels. We do not cover it in BIOL10822 which is a shame because it is the most powerful endogenous vasoconstrictor.
An enzyme-inhibitor drug that increases levels of cAMP in platelets is:
a. alteplase b. aspirin c. clopidogrel d. dipyridamole
d
Dipyridamole’s main mechanism of action is to inhibit phosphodiesterases. These are the enzymes that break down cAMP, so blocking them will raise cAMP levels. Alteplase is an activator of plasminogen, aspirin is an inhibitor of cyclooxygenases, clopidogrel is an irreversible inhibitor of platelet ADP receptors.
What is the target time for treating a thrombus with a thrombolytic drug?
a. 30 min b. 2 hours c. 4.5 hours d. 12 hours
c
Doctors aim to use thrombolytics within 4.5 hours of the initial thrombus forming. Thrombii mature and become resistant to plasmin if left longer.
Which of the following thrombolytics is a mutated version of tissue plasminogen activator?
a. alteplase b. plasmin c. reteplase d. streptokinase
c
Reteplase is a recombinant mutant version of tPA that has better stability in the body. Altplase is a recombinant enzyme identical to tPA. Streptokinase is a bacterial enzyme. Plasmin, of course, is the enzyme that tPA produces by cleaving plasminogen.
Martha recently suffered a stroke. Luckily, she was taken to hospital very quickly and was treated with [______________1], a drug that activates the protease [____________2]. This resulted in the breakdown of the thrombus and restoration of blood flow to the ischaemic area of her brain. After discharge from hospital Martha was prescribed low dose [______________3] to lower the risk of another stroke. This drug irreversibly inhibits the enzyme [________________4] in platelets, preventing them from synthesizing [________________5], a signaling molecule that stimulates platelet aggregation.
- alteplase
- plasmin
- aspirin
- cyclooxygenase 1
- thromboxane A2
