... pyrimidine dione hydrochloride as an active ingredient; and being substantially free of an additive comprising a metal salt. ... Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim. 513. having oxo groups directly attached to the heterocyclic ring, e. ... Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim. 513. having oxo groups directly attached to the heterocyclic ring, e. ... Pyrimidines; Hydrogenated pyrimidines, e.g. trimethoprim. 513. having oxo groups directly attached to the heterocyclic ring, e. ...