Nitroimidazoles

Nitroimidazoles are synthetic antibacterial preparations with a high activity against anaerobic microorganisms and protozoal infections. The first medication - metronidazole was approved for medical use in 1960 year. Another nitroimidazoles include: tinidazole, ornidazole, secnidazole and preparation for local application ternidazole.

Action mechanisms

Nitroimidazoles exert selective bactericidal action against those microorganisms in which enzymatic systems can reduce nitro group. Active reductive forms of medications inhibit DNA replication and protein synthesis in microbial cell and inhibit respiratory chains (cellular respiration).

Spectrum of activity
Nitroimidazoles are active against the majority of gram-negative and gram-positive anaerobs: bacteroides (including B.fragilis), clostridium (including C.difficile), Fusobacterium spp., Eubacterium spp., Peptostreptococcus spp., P.niger, G.vaginalis. P.acnes are resistant to imidazoles.

T.vaginalis, E.histolytica, G.lamblia, L.intestinalis, E.coli, Leishmania spp. are also resistant to nitroimidazoles.

Indications
For systemic use

Anaerobic and mixed aerobic-anaerobic infections of different localization:

  • Lower respiratory tract infections (pneumonia, pleural empyema, pulmonary abscess)
  • CNS infections (meningitis, brain abscess)
  • Intraabdominal infections including pelvic infections
  • Oral cavity infections
  • Pseudomembranous colitis
  • Prophylaxis of infections during intraabdominal and gynecological operations
  • Protozoal infections: trichomoniasis, giardiasis, balantidiasis, amoebiasis and extraenteric amoebiasis (amoebic hepatitis, liver abscess, brain abscess)
  • H.pylori eradications in ulcerous disease (in combination with other preparations)

Locally:

  • Vaginitis
  • Bacterial vaginosis
  • Acne
  • Seborrheic eczema
  • Acne rosacea

Contraindications

  • Organic diseases of the central nervous system
  • Allergic reactions of reactions of hypersensitivity to nitroimidazoles
  • Pregnancy
  • Breastfeeding

Cautions

  • Allergy. Allergic reactions are usually crossed to all nitroimidazoles
  • Pregnancy. Nitroimidazoles penetrate through placenta and creating high concentrations in fetus tissues. They exert mutagenenic and cancerogenic effect. They are contraindicated for use in I, II and III trimester of pregnancy
  • Breastfeeding. Nitroimidazoles penetrate into breast mils. The concentration in the blood plasma in children in 10-20% therefore the use of this group of medicines during breastfeeding is contraindicated
  • Pediatric use. Nitroimidazoles can accumulate in children's organism. In newborns half-life period is increased
  • Geriatric use. The dose should be adjusted in dependence of liver and kidney functions in this category of patients
  • CNS diseases. Nitroimidazoles should be used with caution in patients with organic disorders of central nervous system because Nitroimidazoles possess neurotoxicity and may cause epileptic seizures
  • Stomatology. Metronidazole may cause dry mouth and changes of taste disorders. Dry mouth can provoke caries, oral thrush

Nitroimidazoles side effects

  • In systemic use: taste changes, stomach pain, nausea, vomiting, diarrhea
  • CNS: headache, drowsiness, coordination disorders, confusion, seizures
  • Allergic reactions: skin rash, itching
  • Hematologic reactions: leukopenia, neutropenia
  • Local reactions: phlebitis and thrombophlebitis after intravenous injections
  • In intravaginal use: itching, vaginal and vulva itching, edema, vaginal discharges, frequent urination
  • In local application: dermatological reactions including photodermatitis

Drug interactions

  • Metronidazole, tinidazole and secnidazole affect the metabolism of alcohol and cause disulfiram-like reactions
  • Nitroimidazoles may enhance the effect of anticoagulants
  • The activity of Nitroimidazoles is reduced when used in combination with inductors of microsomal liver enzymes (rifampicin, phenobarbital)

Information for patients:

  • Nitroimidazoles are available in different pharmaceutical forms. Oral forms can be taken with or without food. However, it is more preferably to take during meal to avoid possible stomach disturbances
  • It is necessary to follow all doctor recommendation and instruction during the treatment. If the symptoms does not improve within 7 days it is necessary to consult a doctor
  • Do not take any alcoholic products because of a high risk of disulferam-like reactions
  • Nitroinidazoles may change the color of the urine
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