Water-soluble organic salt. Two references consider it safe. Several observations of non-porphyrinogenicity.

Metenamine hippurate, Largely excreted unchanged but hydrolyzed in the urinay tract to formaldehyde and ammonia, excreted in urine. Previously often in use in acute porphyrias as an antibacterial agent in urinary tract infections. Probably without CYP affinity. South African list: use. Metabolic Basis…ref 279: probably safe. Thunell: On many occasions observed to be tolerated.

Uneventful use reported in 1 patient with acute porphyria.