Biseptol — kombinatsiyalangan antibakterial preparat bo'lib, tarkibida o'rtacha ta'sir davomiyligiga ega bo'lgan sulfaning hosilasi — sulfametoksazol va trimetoprim mavjud. Sulfametoksazol para-aminobenzoy kislotasi (PABK) bilan raqobatli antagonizm orqali foliy kislotasi sintezini susaytiradi, trimetoprim esa bakteriyalarning dihidrofoliy kislotasini tetrahidrofoliy kislotaga aylantiradigan fermentini ingibitsiya qiladi. Bu ikki komponent birgalikda antibakterial ta'sirni kuchaytiradi, natijada bakterial chidamlilik boshqa preparatlarga qaraganda kamroq rivojlanadi.
Biseptol keng spektrli antibakterial ta'sirga ega va quyidagi mikroorganizmlarga nisbatan faol:
Streptococcus (jumladan, Streptococcus pneumoniae),
Neisseria meningitidis,
Neisseria gonorrhoeae (jumladan, enterotoksigenik shtammlar),
Staphylococcus,
Escherichia coli,
Klebsiella spp.,
Enterobacter spp.,
Proteus mirabilis,
Proteus spp.,
Haemophilus influenzae,
Salmonella spp. (jumladan, Salmonella typhi va Salmonella paratyphi),
Vibrio cholerae,
Bacillus anthracis,
Listeria spp.,
Nocardia asteroides,
Bordetella pertussis,
Enterococcus faecalis,
Pasteurella spp.,
Brucella spp.,
Mycobacterium spp. (jumladan, Mycobacterium leprae),
Citrobacter spp.,
Legionella pneumonia,
Providencia spp.,
ayrim Pseudomonas spp. (lekin Pseudomonas aeruginosaga nisbatan emas),
Serratia marcescens,
Yersinia spp.,
Morganella spp.,
Chlamydia spp. (jumladan, Chlamydia trachomatis va Chlamydia psittaci),
Shigella spp.,
Plasmodium spp.,
Toxoplasma gondii,
Pneumocystis carinii,
Actinomyces israelii,
Coccidioides immitis,
Histoplasma capsulatum,
Leishmania spp.
Biseptolga chidamli mikroorganizmlar:
Corynebacterium spp.,
Pseudomonas aeruginosa,
Mycobacterium tuberculosis,
Treponema spp.,
Leptospira spp.,
viruslar.
Preparat ichak tayoqchasining hayot faoliyatini bostiradi va ichakda tiamin, riboflavin, nikotin kislotasi va B guruhi vitaminlari sintezining kamayishiga olib keladi. Terapevtik ta'siri 7 soat davom etadi.