What drug class prevents or delays blood clotting?

• A. Anticoagulant
• B. Antibiotic
• C. Analgesic
• D. Antihistamine

Answer: (A)

Anticoagulants slow or prevent the blood from forming clots by interrupting steps in the coagulation cascade. They can reduce the production or activity of clotting factors, such as vitamin K–dependent factors with drugs like warfarin, or enhance inhibition of thrombin and factor Xa with heparin and its derivatives, or directly block factor Xa or thrombin with newer agents. By dampening these pathways, they lower the risk of thrombosis in conditions like atrial fibrillation, deep vein thrombosis, or pulmonary embolism. They don’t dissolve clots that are already formed; they prevent their growth and the formation of new ones. If clots need to be dissolved, thrombolytics are used instead. The other drug classes don’t affect clot formation: antibiotics target infection, analgesics relieve pain, and antihistamines reduce allergic symptoms.