Lithium-induced nephrogenic diabetes insipidus: renal effects of amiloride.
OBJECTIVE
Polyuria, polydipsia, and nephrogenic diabetes insipidus have been associated with use of psychotropic medications, especially lithium.


METHODS
The impact of psychotropic medications on urinary concentrating ability and urinary aquaporin 2 (AQP2) excretion was investigated after overnight fluid deprivation, and over 6 h after 40 microg of desmopressin (dDAVP), in patients on lithium (n = 45), compared with those on alternate psychotropic medications (n = 42).


RESULTS
Those not on lithium demonstrated normal urinary concentrating ability (958 +/- 51 mOsm/kg) and increased urinary excretion of AQP2 (98 +/- 21 fmol/micromol creatinine) and cAMP (410 +/- 15 pmol/micromol creatinine). Participants taking lithium were divided into tertiles according to urinary concentrating ability: normal, >750 mOsm/kg; partial nephrogenic diabetes insipidus (NDI), 750 to 300 mOsm/kg; full NDI, <300 mOsm/kg. Urinary AQP2 concentrations were 70.9 +/- 13.6 fmol/micromol creatinine (normal), 76.5 +/- 10.4 fmol/micromol creatinine (partial NDI), and 27.3 fmol/micromol creatinine (full NDI). Impaired urinary concentrating ability and reduced urinary AQP2, cAMP excretion correlated with duration of lithium therapy. Other psychotropic agents did not impair urinary concentrating ability. Eleven patients on lithium were enrolled in a randomized placebo-controlled crossover trial investigating the actions of amiloride (10 mg daily for 6 wk) on dDAVP-stimulated urinary concentrating ability and AQP2 excretion. Amiloride increased maximal urinary osmolality and AQP2 excretion.


CONCLUSIONS
By inference, amiloride-induced reduction of lithium uptake in the principal cells of the collecting duct improves responsiveness to AVP-stimulated translocation of AQP2 to the apical membrane of the principal cells.
Bedford
Jennifer J
JJ
Department of Medical & Surgical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand.
Weggery
Susan
S
Ellis
Gaye
G
McDonald
Fiona J
FJ
Joyce
Peter R
PR
Leader
John P
JP
Walker
Robert J
RJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D000584:Amiloride / Q000627:therapeutic use*; D051399:Aquaporin 2 / Q000652:urine; D003404:Creatinine / Q000652:urine; D018592:Cross-Over Studies; D003430:Cross-Sectional Studies; D000242:Cyclic AMP / Q000652:urine; D003894:Deamino Arginine Vasopressin / Q000008:administration & dosage; D018500:Diabetes Insipidus, Nephrogenic / Q000139:chemically induced / Q000188:drug therapy* / Q000652:urine; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007671:Kidney Concentrating Ability / Q000187:drug effects*; D007685:Kidney Tubules, Collecting / Q000187:drug effects* / Q000378:metabolism; D018020:Lithium Compounds / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D019964:Mood Disorders / Q000188:drug therapy* / Q000652:urine; D045283:Natriuretic Agents / Q000627:therapeutic use*; D009994:Osmolar Concentration; D011619:Psychotropic Drugs / Q000009:adverse effects*; D013997:Time Factors; D016896:Treatment Outcome; D014868:Water Deprivation
C496023:AQP2 protein, human; D051399:Aquaporin 2; D018020:Lithium Compounds; D045283:Natriuretic Agents; D011619:Psychotropic Drugs; D000584:Amiloride; D003404:Creatinine; D000242:Cyclic AMP; D003894:Deamino Arginine Vasopressin