Phthalazole (Phthalazolum)

Phthalazole, like other sulfonamide preparations similar in structure to para-aminobenzoic acid, prevents the inclusion of it in the synthesis of folic acid involved in the synthesis of purine and pyrimidine bases on which the growth and development of microorganisms depends.

The most pronounced bacteriostatic effect of phthalazole is on vegetative forms of microbes. This effect develops gradually, since there are reserves of para-amino-benzoic acid in the microbial cell.In addition, the degree of affinity of phthalazole with synthetase dihydrofolic acid, an enzyme that limits the formation of folic acid, is considerably weaker in comparison with para-aminobenzoic acid. Therefore, phthalazole must be administered at sufficiently high doses that prevent the use of parahaminobenzoic acid contained in the tissues by microorganisms. Otherwise, resistant strains of pathogens can be formed, which can not be further affected by sulfanilamide preparations. In addition to antibacterial, phthalazole, like other sulfonamide preparations, has an anti-inflammatory effect that is associated with its ability to limit the migration of leukocytes, reduce the total number of migrating cellular elements and partially stimulate the production of glucocorticosteroids.

The spectrum of antimicrobial action of phthalazole, like other sulfonamides, is narrower than antibiotics. Sulfanilamides exert bacteriostatic action on Streptococcus spp. (including Streptococcus pneumoniae), Staphylococcus spp :, Neisseria meningitidis, Neisseria gonorrhoeae; Escherichia coli, Pseudomonas aeruginosa, Shigella dysenteriae, Proteus vulgaris and a number of large viruses - causative agents of trachoma and follicular conjunctivitis.