Sketchy Pharm: Heparin, LMWH, Fondaparinux, Direct Thrombin Inhibitors, Xa Inhibitors

Question 1

What enzyme converts fibrinogen to fibrin?

Answer 1

Thrombin (just like the throm-beaver modifying the little sticks to create a fibrin dam); thrombin is also called factor II (just like the beaver’s two front teeth)

Question 2

What activates thrombin?

Answer 2

Activated factor X (just like the Angry FoX attacking the throm-beaver )

Question 3

What is the category that heparin and the related heparin drugs falls into?

Answer 3

Indirect thrombin inhibitors

Question 4

How does heparin work?

Answer 4

Heparin –an endogenous protein –binds antithrombin (aka factor III) and enhances its activity a thousand fold. Antithrombin deactivates IIa, VIIa, IXa, Xa, XIa, and XIIa

Question 5

Those receiving heparin require close monitoring of _______.

Answer 5

aPTT (like the hunter monitoring the woodpecker going PTTTTTTTT)

Question 6

Important to know, heparin is not a __________. Thus, if given for a DVT (which it should), it will only prevent ___________.

Answer 6

clot-buster; further enlargement of the clot

Question 7

What are signs of PE?

Answer 7

Pleuritic cough and shortness of breath

Question 8

True or false: heparin should be given to someone with an MI.

Answer 8

True. This prevents fibrin-based enlargement of the thrombus. (Think of the guy in the tree next to the PE woodpecker playing the banjo with broken heart strings.)

Question 9

_____________ usually occurs after seven days of heparin administration.

Answer 9

Heparin-induced thrombocytopenia

Question 10

_______________ paradoxically presents with clots.

Answer 10

Heparin-induced thrombocytopenia (because the antibodies to the receptors on platelets cause the platelets to rupture, thus starting a clot)

Think of the beaver building a dam around the hunter shooting four discs (because PF-4 is the receptor which antibodies bind to).

Question 11

Heparin use can lead to a mineralocorticoid disorder. What is it?

Answer 11

Hypoaldosteronism, due to damage of the adrenal medulla. This presents with hyperkalemia, because aldosterone spurs the excretion of potassium.

(Think of the MINERAL mine that you could fall into –representing hypoaldosteronism – and the big K boarded over it.)

Question 12

Why might you need to give a vitamin supplement to someone taking long-term heparin?

Answer 12

Because it can cause osteoporosis (so give vitamin D)

Question 13

What is the antidote to heparin-induced bleeding?

Answer 13

Protamine sulfate (think of the PROTected Area)

Question 14

Enoxaparin is able to do what?

Answer 14

Enoxaparin is low-molecular weight heparin (a category of drugs that end in -parin) that can inactivate Xa, while unfractionated heparin can also inhibit IIa.

Think of the daughter hunter (who is smaller than the father, just like LMWH) only able to trap the FoX with her little cage.

Question 15

True or false: LMWH overdose can also be treated with protamine.

Answer 15

False.

Think of the little hunter girl who is able to sneak past the protamine fence.

Question 16

What are some pharmacokinetic/pharmacodynamic advantages of LMWH?

Answer 16

It can be given subcutaneously and it has a long half life (just like the long, tapering flag that the girl is carrying).

Also, because it doesn’t have as strong of an effect as unfractionated heparin, it doesn’t require aPTT monitoring (just like how the girl doesn’t care where the woodpeckers are).

Question 17

The main precaution needed with LMWH is _____________.

Answer 17

renal monitoring –it is renally excreted, so be careful in giving it to those with renal failure (think of the girl stabbing the flag into the kidney-shaped rock)

Question 18

True or false: LMWH is category X in pregnancy.

Answer 18

False. The heparin drugs are safe to give to pregnant women –in fact, LMWH is the preferred anticoagulant in pregnant women because warfarin is category X.

Question 19

All types of heparin can cause __________, but it is less common in LMWH.

Answer 19

HIT

Question 20

Fondaparinux has what mechanism?

Answer 20

Like LMWH, it can only assist IIIa in inactivating Xa (like the FiDo dog with the PAiR of FoXs)

Question 21

What are the direct thrombin inhibitors?

Answer 21

The -rudins: bivalirudin (think of the no intRUDIN’ sign above the gators who are eating the thrombeavers)

The -gatr-s: dabigatran and argatroban (like the GAToRs eating the thrombeavers)

Question 22

What are the Xa inhibitors?

Answer 22

The name spells it out for you: enoxaban and abixaban… they BAN Xa!

Think of the FoXes being BANned.

Question 23

What is pharmacokinetically helpful about Xa inhibitors?

Answer 23

They can be given orally (because of this, they’re commonly used for atrial fibrillation).