Which of the following diuretics decrease the renal lithium clearance?
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
acetazolamide
hydrochlorthiazide
furosemide
spironolectone
Diuretic