What class of drugs decreases the blood's ability to clot?

• A. Antihistamines
• B. Anticoagulants
• C. Antibiotics
• D. Antidepressants

Answer: (B)

Anticoagulants decrease the blood’s ability to clot by interrupting the coagulation cascade or platelet function, which slows or prevents the formation of clots. They act on factors in the clotting pathway (for example, warfarin inhibits vitamin K–dependent factors, heparin enhances antithrombin III to block thrombin and factor Xa, and direct oral anticoagulants target thrombin or factor Xa). This is why they’re described as “blood thinners”—they reduce clot formation and are used to prevent conditions like deep vein thrombosis, pulmonary embolism, or stroke in atrial fibrillation.

Antihistamines treat allergic symptoms, antibiotics target infection, and antidepressants affect mood and, in some cases, platelet function, but they do not form a primary class whose main purpose is to prevent clotting like anticoagulants do.