Impact of sodium-potassium citrate therapy on the circadian rhythm of urinary uric acid and urate saturation in normal individuals.

The circadian rhythm of the urinary saturation of uric acid, sodium acid urate, and ammonium acid urate was studied in 5 normal healthy male volunteers 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.). Urinary saturation was estimated on the relative supersaturation scale of Marshall and Robertson. Uric acid relative supersaturation varied during the day (mean +/- SD: -1.297 +/- 1.763) and peaked above the formation product between 5:30 and 8:00 am. The peak level was reduced (but not significantly) by each treatment regimen in comparison with the control day. Overall, critical supersaturation with uric acid was noted in 46 (13%) out of 345 urine specimens, occurring mostly (83%) between 5:30 and 8:00 am. The sodium acid urate relative supersaturation also varied during the day (mean +/- SD: 0.329 +/- 0.305) and peaked below the formation product between 8:00 and 10:30 am. It was increased by each regimen (significantly by the 3 g t.i.d. regimen), but mostly remained in or below the metastable zone. The ammonium acid urate relative supersaturation also varied (mean +/- SD: 0.087 +/- 0.301) and peaked below the formation product between 5:30 and 8:00 am. The level was decreased by each regimen and remained in or below the metastable zone throughout the day. In conclusion, the early morning period was the time with the highest risk of urinary uric acid supersaturation, but this supersaturation could be reduced (although not significantly) by treatment with alkali citrate.(ABSTRACT TRUNCATED AT 250 WORDS)