title: Safety of furosemide administration in an elderly woman recovered from thiazide-induced hyponatremia.
abstract: BACKGROUND
  Elderly women are at risk to develop severe hyponatremia after thiazide but not loop diuretic administration. In patients with previous thiazide-induced hyponatremia, the risk for recurrent hyponatremia after furosemide has not been established.
  
  
  METHODS
  In order to determine how both diuretics affect water metabolism, we here compare the effects of a rechallenge with either amiloride-hydrochlorothiazide fixed association (AmHTZ; amiloride chlorhydrate 5 mg+hydrochlorothiazide 50 mg; Moduretic) or furosemide (F; 40 mg; Lasix) on water excretion in a 79 year old woman who was previously admitted for severe symptomatic hyponatremia secondary to a 5 days course of AmHTZ for systolic hypertension. After correction of initial hydromineral disturbances, a standard oral water load (WL; 20 mL per kg body weight) was administered before, during and after AmHTZ or F challenges.
  
  
  RESULTS
  Hyponatremia developed after AmHTZ but not after F challenge. A negative free water clearance (CH(2)O) was only observed during AmHTZ (-0.39 mL/min), while maximal CH(2)O during F was 3.17 mL/min. Based on the results obtained during WL, the calculated maximal daily electrolyte free water clearance ability was only 888 mL after AmHTZ but 10,166 mL after F therapy. Taking into account a measured mean daily water intake of 1830 mL, severe hyponatremia could be predicted to occur after a few days treatment with AmHTZ. In comparison, F appears to be safer, without risk of hyponatremia, during an equivalent period of time.
  
  
  CONCLUSIONS
  We here showed that F may be administered to a patient with previous AmHTZ induced hyponatremia without risk for recurrent hyponatremia.
authors.affiliation: Department of Internal Medicine, Hôpital Erasme, 808, route de Lennik 1070 Brussels Belgium, Université Libre de Bruxelles, U.L.B, Belgium.
authors.forename: Safia
authors.initials: S
authors.lastname: Fadel
authors.forename: Rafik
authors.initials: R
authors.lastname: Karmali
authors.forename: Elie
authors.initials: E
authors.lastname: Cogan
mesh_terms: D000368:Aged; D004232:Diuretics / Q000008:administration & dosage* / Q000009:adverse effects*; D004326:Drinking; D005260:Female; D005665:Furosemide / Q000008:administration & dosage*; D006801:Humans; D006852:Hydrochlorothiazide / Q000009:adverse effects*; D006973:Hypertension / Q000188:drug therapy*; D007010:Hyponatremia / Q000139:chemically induced*; D008954:Models, Biological; D009318:Natriuresis / Q000187:drug effects
chemical_list: D004232:Diuretics; D006852:Hydrochlorothiazide; D005665:Furosemide