This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diuretic, Subject name: Pharmacology
Which of the following diuretics decrease the renal lithium clearance? 
Select and explain. 
A. acetazolamide, B. hydrochlorthiazide, C. furosemide, D. spironolectone
B: hydrochlorthiazide
Answer: B: hydrochlorthiazide 
Explanation: Ans. is 'b' i.e., hydrochlorothiazide Lithium has got low therapeutic index so measuring its plasma level is of utmost importance to assure safe use of drugApproximately 95% of a single dose of Li+ is eliminated in urine.Li+ is handled by the kidney in same way as Na+ i.e. most of the filtered Li+ is reabsorbed in the proximal tubule. So loading with Na+ will increase the Li+ excretion and Na+ depletion will promote a clinically important degree of retention of Li+It is now obvious that diuretics will cause retention of Li+ because they cause Na+ depletion.All the diuretics given in option (except Acetazolamide) decrease the renal lithium clearance.So we will have to choose the one, which causes the greatest retention of lithium.Goodman Gilman (10/e, p 509) and Katzung (8/e, p 493) write that the thiazide cause greatest retention among diuretics.Other drugs which can cause Li retentionTetracyclineIndomethacinACE inhibitors