Drug Mechanisms: Direct Factor X-a Inhibition

The question asks to identify a drug that directly inhibits Factor X-a. Factor X-a is a crucial enzyme in the coagulation cascade, responsible for converting prothrombin to thrombin.

Analyzing Drug Options

Let's examine the mechanism of action for each option:

• Tirofiban: This drug is a platelet aggregation inhibitor, specifically blocking the glycoprotein IIb/IIIa receptor. It does not directly inhibit Factor X-a.
• Apixaban: This is an anticoagulant that directly and selectively inhibits Factor X-a. It prevents thrombin generation by blocking the activity of Factor X-a.
• Dabigatran: This drug is a direct thrombin (Factor IIa) inhibitor. It inhibits the final step of the coagulation cascade but does not directly inhibit Factor X-a.
• Prasugrel: This is an antiplatelet medication that irreversibly blocks the P2Y12 receptor on platelets. It affects platelet function, not the coagulation cascade factors like X-a.

Conclusion

Based on the mechanisms, Apixaban is the drug that causes direct Factor X-a inhibition.