This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Pharmacology
Which stone is common in chronic laxative use: 
Select and explain. 
A. Xanthine, B. Cysteine, C. Ammonia urate, D. Struvite
C: Ammonia urate
Answer: C: Ammonia urate 
Explanation: Ans. c. Ammonia urateRef: Campbells Urology/P. 210Chronic laxative use leads to decreased sodium in the urine, as most sodium is excreted by GIT.Hence urate binds more with ammonia and this leads to ammonia urate stones.