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Tetracycline mechanism of action
- protein synthesis inhibitors
- bindd to 30s subunit of bacterial ribosome
- Blocks aminoacyl-TtRNA to acceptor site on the mRNA-ribosome complex.
- prevents addition of amino acids to growing peptide.
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Tetracycline is a derivative of what?
polycyclic naphthacene carboxamide
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Tetracycline (general info)
- crystalline amphoteric
- low solubility
- hydrochloride more soluble
- Tetracycline hydrochlorides solution are fairly stable (except chlortetracycline
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When do tetracyline loose activity?
- when they chelate into divalent metal ions
- this interfere with absorption and activity
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Tigecycline
treat infection that are resistant to other antimicrobics including conventional tetracyclines
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Tetracycline antimicrobial activity
- broad spectrum bacteriostatic, inhibit protein synthesis
- against gram+ and gram -
- enter microorganism by passive diffusion and in part by energy dependent process of active transport
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Tetracycline resistant strains may be susceptible to...
doxycyline, minocycline, and tigycycline which are poor substrates for efflux pump.
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Mechanism 1 of resistance for tetracycline
impaired influx or increase efflux by an active transport protein pump.
most important: are production of efflux pump and ribosomal protection.
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Mechanims 2 of resistance for tetracycline
ribosome protection due to production of proteins that interfere with tetracycline binding to ribosome
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Mechanism 3 of resistance for tetracycline
enzymatic inactivation of tetracycline
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Mechanism of action of protective protein for tetracycline resistance
- 1: blocking tetracycline from binding to ribosome
- 2: binding to ribosome and distorting the structure to still allow t-RNA binding while tetracycline is bound
- 3: binding to the ribosome and dislodging tetracycline
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Tet(M)
- ribosomal protection protein expressed by gram + to create resistance against tetracycline, doxycyline, and minocycline
- but not tigecycline
- Steric hindrance effect due to t-butylglycylamido substituent
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Enzymatic inactivation
- rarest type of resistance
- acetyl group is added to tetracycline causeing inactivation of drug.
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Absorption for oral administration for tetracyclines
- 30% for chlortetracycline
- 60-70% for tetracycline, oxytetracycline, demeclocycline, and methacycline
- 95-100% for doxycyline and minocycline
- poor oral absorption for tigecycline and must be administered intravenously
- portion of tetra dose remains in gut and modifies intestinal flora, excreted in feces
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Tetracycline occurs mainly where?
upper small intestines
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What interfers with tetracycline absorption?
food (except doxy and mino), divalent cations, dairy products and antacids, and alkaline pH
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How are tetracylines recommended to take?
- with a full glass of water
- 1 hours before and 2 hours after eating
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Specially buffered tetracyclines are used for what?
IV administration
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Tetracyclines are what percent bound to proteins?
40-80%
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