From uron, urine, and trepo, to change, a proprietary-designation of a remedy intended to remove certain morbid states of the genito-urinary apparatus. It is formed by the combination of ammonia and formaldehyde, and occurs as colorless crystals, readily soluble in water. The dose for internal administration is usually about thirty grains per diem, or five to ten grains every four hours. It is readily diffusible, and appears in the urine in about fifteen minutes after it is swallowed. Either urotropin or its constituent, formaldehyde, is always to be found in the blood or urine in its passage through the system. When given in full doses, it may cause a sensation of heat, even burning along the course of the urethra or at the neck of the bladder, and increase the desire to urinate.

The most important property of urotropin is to render urine acid again that had become alkaline. This it accomplishes by inhibiting the septic organisms, that being about the alkalinity.

Urotropin has been used with success in effecting the solution of uric acid calculi. In pyonephrosis, with or without phosphatic concretions, it has restored the integrity of the mucous membrane, and stopped permanently the process of suppuration. Much relief has been effected by its use in enlarged prostate, with the resulting alterations in the bladder.