Effects of theophylline on urinary excretion of cyclic AMP, calcium, and phosphorus in normal subjects.

The present study was designed to examine the effects of acute theophylline administration on urinary excretion of cyclic adenosine monophosphate (cAMP), calcium, and phosphorus in normal subjects. The results demonstrated that at therapeutic doses (5 mg i.v./kg body weight) theophylline exerted a distinct biologic effect on renal tubular activity in 5 normal subjects: an increase in nephrogenous cAMP accompanied by a rise in phosphate and calcium urinary excretion. Beyond the clinical implications, the data suggest that theophylline, in contrast to parathyroid hormone, may be acting via cAMP to exert both its phosphaturic and calciuric effect on renal tubules.