This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Ursodeoxycholic acid is a : 
Select and explain. 
A. Urinary stone dissolving drug, B. Thrombolytic drug, C. Gall stone dissolving drug, D. Antifibrinolytic
C: Gall stone dissolving drug
Answer: C: Gall stone dissolving drug 
Explanation: • Medical therapy for gallstones utilizes bile acids: Chenodeoxycholic acid (CDCA) and Ursodeoxycholic acid (UDCA)
Mechanism of Action
• They inhibit HMG-CoA reductase, the rate limiting enzyme for cholesterol synthesis, thus decreases cholesterol saturation of bile
• They cause dispersion of the cholesterol from the stones by physico-chemical means