This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pharmacology
Tolvaptan is used for: 
Select and explain. 
A. SIADH, B. Central DI, C. Von Willebrand disease, D. Catecholamine resistant shock
A: SIADH
Answer: A: SIADH 
Explanation: Ans. (A) SIADH(Ref: Harrison 20th/302)Vaptans like tolvaptan are vasopressin receptor antagonists.V1 receptor antagonists may be useful when total peripheral resistance is increased (e.g. CHF and hypertension) whereas V2 antagonists may be useful for the treatment of SIADH.Relcovaptan is selective V1 antagonist whereas lixivaptan, mozavaptan and tolvaptan are V2 selective antagonists.Conivaptan is V1a/V2 receptor antagonist used as an aquaretic (increase water excretion without affecting electrolytes like sodium) in CHF.Conivaptan is administered by i.v. injection whereas lixivaptan and tolvaptan can be given orally.