18. Metronidazole. Fidaxomicin. Rifaximin. Urinary antiseptics. Phosphomycin Flashcards
Metronidazole
Tinidazole
Produces toxic intermediate metabolites (reduction of N2O group) in anaerobic conditions
Bactericidal (and amebicidal)
Spectrum: Anaerobic bacteria (bacteroides and clostridium) | Protozoa (trichomonas, G.lamblia, amoeba, entameba histolytica)
Distribution: good absorption, wide distribution (CNS and abscesses) vaginal and seminal fluids, saliva, breast milk
Administration: Oral, IV and topical
Metabolism: Hepatic oxidation (CYP450) and glucuronidation
Excretion: Urine
Adverse effects: GI (nausea), metallic taste, alcohol-intolerance (disulfiram-like reaction)
Fidaxomicin
Protein synthesis inhibitor - Inhibits RNA polymerase - disruption of transcription
Bactericidal
Spectrum: Narrow, G+ive (c.difficile)
Distribution: minimal absorption
Administration: Oral
Adverse effects: GI (nausea, vomiting), hypersensitivity
Rifaximin
Rifampicin group
Interacting with DNA dependent RNA polymerase
Rifaximin is a semisynthetic, rifamycin-based non-systemic antibiotic.
Spectrum: G+ive (staphylo, strepto, enterococcus) | G-tive (moderate action against the intestine bacteria)
Kinetics: Oral administration | does no absorb from the GI!!
Indications: Hepatic encephalopathy, Prophylaxis before colorectal surgery, Acute (non inflammatory) enteritis (drug of choice), Colitis
Urinary antiseptics
Nitrofurans
Methenamine
Phosphomycin
Cell wall synthesis inhibitor (Inhibits the first step in formation of UDP-N-acetylmuramic acid)
Bactericidal
Spectrum: G+ive and G-ive (ESBL E.coli), E.faecalis
Administration: oral or parenteral (no minimal 7 days administration - maintaining concentration in the urine)
Kinetics: good absorption, kidney, bladder, prostate
Excretion: Urine and feces
Adverse effects: moderate GI symptoms
Metronidazole
Metronidazole
Tinidazole
differences between Tinidazole & Metronidazole
2nd generation metronidazole
shorter course of treatment, more expensive
Methenamine
Urinary antiseptics
Decomposes to formaldehyde in acidic pH (toxic for bacteria)
Administration: oral
Indications: Chronic suppressive therapy for UTI
Adverse effects: GI distresses
Nitrofurantoin
Nitrofurans
Damages bacterial DNA - reduced to highly active intermediates
Spectrum. E.coli, E.faecalis, sprofiticus
Kinetics: high concentration only in the urine
Indication: uncomplicated lower UTI (in pregnancy, in children, in case of resistance)
Adverse effects: GI symptoms | Acute hypersensitivity pulmonary reaction, chronic pulmonary reaction | Neuropathies
Nitrofurans
Nitrofurantoin
