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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.
Tetracycline is a derivative of what?
polycyclic naphthacene carboxamide
Tetracycline (general info)
- crystalline amphoteric
- low solubility
- hydrochloride more soluble
- Tetracycline hydrochlorides solution are fairly stable (except chlortetracycline
When do tetracyline loose activity?
- when they chelate into divalent metal ions
- this interfere with absorption and activity
treat infection that are resistant to other antimicrobics including conventional tetracyclines
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
Tetracycline resistant strains may be susceptible to...
doxycyline, minocycline, and tigycycline which are poor substrates for efflux pump.
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.
Mechanims 2 of resistance for tetracycline
ribosome protection due to production of proteins that interfere with tetracycline binding to ribosome
Mechanism 3 of resistance for tetracycline
enzymatic inactivation of tetracycline
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
- 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
- rarest type of resistance
- acetyl group is added to tetracycline causeing inactivation of drug.
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
Tetracycline occurs mainly where?
upper small intestines
What interfers with tetracycline absorption?
food (except doxy and mino), divalent cations, dairy products and antacids, and alkaline pH
How are tetracylines recommended to take?
- with a full glass of water
- 1 hours before and 2 hours after eating
Specially buffered tetracyclines are used for what?
Tetracyclines are what percent bound to proteins?