USMLE Step 1 First Aid: Heme/Onc Pharmacology Final Exam with Already Solved Solutions Updated.

USMLE Step 1 First Aid: Heme/Onc
Pharmacology Final Exam with
Already Solved Solutions 2025-2026
Updated.
Heparin

Mechanism - Answer Inhibits *Thrombin* and *Factor Xa* (promotes antithrombin III)



Short half-life



*DOES NOT cross placenta* —> Safe for use during pregnancy



Aspirin

Mechanism - Answer Irreversible COX1/2 inhibitor --> Decreases PGI2 and TXA2



Heparin

Clinical use - Answer PE

ACS

MI

DVT



Anticoagulants of choice in *pregnancy* (does not cross placenta)



Co-administration of heparin can help "bridge" a patient past the *transient hypercoagulation
phenomena* associated w/warfarin tx initiation



Dose-dependent



Aspirin

Clinical use - Answer Pain

Fever

,Aspirin

Adverse effects - Answer Allergies

GI bleeding

Tinnitus

*Reye's syndrome*



Heparin

Adverse effects - Answer Bleeding

*Thrombocytopenia (HIT)*

Osteoporosis

Drug-drug interactions



*Monitor w/PTT or anti-Factor Xa assay*



*REMINDER* PTT measures intrinsic pathway activity



Heparin

Rapid reversal - Answer Use *protamine sulfate* (positively charged molecule that *binds*
negatively charged heparin)



Low-molecular-weight heparin (LMWH) - Answer *E*noxa*parin*, *D*alte*parin* -->
Inhibits *Thrombin* (promotes antithrombin III) and *Factor Xa*, *BUT favors Factor Xa
inhibition*; not easily reversible



Fonda*parin*u*X ONLY inhibits Factor Xa (like direct Factor Xa inhibitors); NO REVERSAL
AGENT*



Dose independent and easy to administer

*NO* monitoring required

*Better bioavailability and 2-4x longer half life than unfractionated heparin*



*B*emi*parin*, *C*erto*parin* are ultra-low-molecular-weight heparins

, Direct Thrombin Inhibitors - Answer *B*ivalirudin

*A*rgatroban

*D*abigatran



*BAD*



Direct Thrombin Inhibitor

Mechanism - Answer Directly binds and inhibits *Thrombin (Factor IIa)*



Unfractionated heparin vs. LMWH vs. Fondaparinux - Answer Unfractionated heparin
inhibits *Factor Xa and Thrombin*



LMWH (*E-, D-parin*) inhibits Factor Xa and thrombin, *BUT favors Factor Xa inhibition*



Fonda*parin*u*X* promotes inhibition of *Factor Xa only*



Direct Thrombin Inhibitor

Clinical use - Answer *Anticoagulate patients w/heparin induced thrombocytopenia* (HIT)

Venous thromboembolism

A-fib



No monitoring required



Direct Thrombin Inhibitor

Adverse effects - Answer Bleeding



*Reverse Dabigatran with Idarucizumab*



Consider *PCC (prothrombin complex concentrates) and/or antifibrinolytics (tranexamic acid)*
if *NO* reversal agent available




Warfarin