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Mechanism of Action (Tetracyclines)
Protein synthesis inhibitor
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Spectrum of Activity (Tetracyclines)
- CA-MRSA
- S. pneumoniae and othe Streptococci
- Enterococcus - poor activity
- H. Flu
- M. catarrhalis
- Moderate to poor against Enterobacteriacea
- Used in combinations for H. pylori
- DOC for Brucella spp. and Vibrio Cholerae
- Excellent against spirochetes, Rickettsia, Chlamydia and Mycoplasma
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Mechanisms of Resistance (Tetracyclines)
- Efflux (Do not affect doxycycline or minocycline)
- Ribosomal Protection Proteins
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Bioavailability (Tetracyclines)
- Tetracyline 60-80%
- Doxycycline 90-100%
- Minocycline 90-100%
- Food and milk decrease absorption
- Do not take with an antacid.
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Distribution (Tetracyclines)
- Excellent tissue penetration
- Lipophilicity: Tetra < Doxy < Mino
CNS penetration follow lipophilicity
Readily cross placenta and into breast milk
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Tetracycline
- Bioavailability: 60-80%
- Minimal hepatic metabolism
- Eliminated 60% unchanged in urine, significatnt bile/fecal elimination
- Half Life: approx. 6 hr
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Doxycycline
- Bioavailability: 90-100%
- Hepatic Metabolism: approx 50%
- Elimination: 20-30% in urine, remainder in bile/feces
- Half Life: 15-24 hrs
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Minocycline
- Bioavailabity: 90-100%
- Hepatic Metabolism: more than 50%
- Elimination: Approx. 10% in urine, remainder in bile/feces
- Half Life: 11-22 hrs
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Adverse Effects (Tetracyclines)
- Gastrointestinal (worst with tetracycline)
- Photosensitivity
- Hepatitis (rare)
- Hypersensitivity (uncommon)
- Tooth discoloration
- Antianabolic effects
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Precautions (Tetracyclines)
- Should not be used in pregnant or breastfeeding women
- Cause inhibtion of bone growth in fetus.
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Therapeutic Uses (Tetracyclines)
- Rickettsial Infections
- Lyme Disease
- Acne (minocycline) - When systemic antibiotic is required
- Acute exacerbations of chronic bronchitis
- SIADH (Syndrome of Inappropriate Antidiuretic Hormone)
- Prevention of Travelers Diarrhea (Doxycycline) - Not recommended
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Drug Interactions (Tetracyclines)
- Antacids
- Calcium supplements
- Iron supplements
These Chelate with tetracyclines
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Mechanism of Action (Tigecycline)
Prevents protein synthesis by binding to 30S ribosomal subunit
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Spectrum of Activity (Tigecycline)
- S. aureus (including MRSA)
- Entercoccus spp.
- S. pheumoniae
- Enterobacteriaceae
- Acinetobacter spp
- Pseudomonas - poor activity
- Good anaerobic coverage.
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Tigecycline
- In quassi-class called gylcylcylcines
- Derivative of minocycline
- IV only
- Biliary elimination
- Half Life: 36 hrs
- Usually dosed BID because more likely to vomit with once daily.
- Good tissue penetration, with slow release from tissues.
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Therapeutic Uses (Tigecycline)
- Complicated skin and skin structure infections
- Intra-abdominal infections
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Adverse Reactions (Tigecycline)
Nausea/vomiting (approx. 30%)
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