Some metabolic aspects of tetracyclines

The clinical literature is reviewed, and new data are presented concerning the increased urinary nitrogen losses which may occur in patients with tetracycline antibiotics. The nitrogen losses may be substantial enough in some to result in negative nitrogen balance. A recently reported effect of tetracycline is the increased excretion of sodium. This may be unrelated to the systemic nitrogen‐losing effect and reflect a diuretic action on the kidneys. Potassium losses are less significant, being at most those expected to accompany the nitrogen losses.