title: Impact of citrate therapy on the circadian rhythm of urinary magnesium ammonium phosphate saturation in normal individuals.
abstract: BACKGROUND
  Alkaline citrate has been used widely in the prevention of stone formation. However, the risk of struvite stone during the alkalinizing therapy has not been adequately studied in terms of magnesium ammonium phosphate saturation.
  
  
  METHODS
  The circadian rhythm of the urinary saturation of magnesium ammonium phosphate was estimated by using the differential Gibbs' free energy values of magnesium ammonium phosphate before and during 5 days of treatment with sodium-potassium citrate (1 g t.i.d., 1 g q.i.d. or 3 g t.i.d.) in five healthy male volunteers.
  
  
  RESULTS
  The magnesium ammonium phosphate saturation varied during the day, peaking far below the solubility product between 08.00 and 10.30 h and between 13.00 and 18.00 h. The mean peak levels were increased by each treatment regimen in comparison with the control day. The mean increase on day 1 was significant between 10.30 and 23.00 h with the 3 g t.i.d. regimen, but the mean saturation still remained below the solubility product throughout the day.
  
  
  CONCLUSIONS
  The urinary magnesium ammonium phosphate saturation appeared hard to exceed the solubility product with a high dose of alkaline citrate.
authors.affiliation: Department of Urology, Faculty of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan. ogawa@med.u-ryukyu.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Ogawa
authors.forename: K
authors.initials: K
authors.lastname: Sugaya
authors.forename: Y
authors.initials: Y
authors.lastname: Koyama
authors.forename: T
authors.initials: T
authors.lastname: Hatano
mesh_terms: D000328:Adult; D002614:Chelating Agents / Q000494:pharmacology*; D002940:Circadian Rhythm; D019343:Citric Acid / Q000494:pharmacology*; D006801:Humans; D017616:Magnesium Compounds / Q000652:urine*; D008297:Male; D009994:Osmolar Concentration; D010710:Phosphates / Q000652:urine*; D012016:Reference Values; D012995:Solubility; D000069877:Struvite
chemical_list: D002614:Chelating Agents; D017616:Magnesium Compounds; D010710:Phosphates; D019343:Citric Acid; D000069877:Struvite