1. About half of our asthmatic patients on long-term treatment with prednisone developed nocturia.
2. This is due to reversal of the normal circadian rhythm of water and electrolyte excretion and is partially corrected within 48 hr of stopping treatment.
3. The disturbance in water and electrolyte excretion appeared to be due to a decrease in proximal tubular reabsorption of sodium at night. This was not directly related to a change in the secretion of Cortisol, aldosterone or antidiuretic hormone.