Which medication classification reduces vitamin K–dependent clotting factors and is used to prevent thrombosis?

• A. Antacids
• B. Antivirals
• C. Antibiotics
• D. Anticoagulants

Answer: (D)

Anticoagulants act to prevent thrombosis by lowering the activity of vitamin K–dependent clotting factors. Vitamin K is required to activate factors II, VII, IX, and X; anticoagulants such as warfarin inhibit the enzyme that recycles vitamin K, reducing these factors and prolonging clotting time. This makes the blood less likely to form dangerous clots, which is why this class is used to prevent thrombosis in conditions like deep vein thrombosis, pulmonary embolism, stroke risk from atrial fibrillation, or after valve replacement. The other options don’t work by this mechanism: antacids alter stomach acid, antivirals target viruses, and antibiotics target bacteria. (Note: antibiotics can interact with anticoagulants by affecting gut bacteria and vitamin K, but they are not the class that directly reduces vitamin K–dependent clotting factors.)