1. Broad-spectrum antibiotics
Chapter 37
Broad-spectrum antibiotics
Tetracycline
Chloramphenicol
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2. Part 1 Tetracyclines Pharmacokinetics
Oral absorption: incomplete; avoid use with milk, iron preparation and anti-acid drugs.
Distribution: widely; easy to accumulate in bone and teeth.
Excretion: mainly from bile and urine; exists enterohepatic circulation.
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3. Antimicrobial activity, mechanism, and spectrum
1. Efficacy: quick bacteriostatic; 2. Mechanism: inhibit bacterial protein synthesis by binding to the 30S subunit and blocking tRNA binding to the A site. 3. Spectrum: broad spectrum of activity • G+菌：＜penicillin, cephalosporin • G-菌：＜aminoglycosides • Others: chlamydia, mycoplasma, rickettsia, leptospira, amoeba.
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4. Therapeutic uses
1. Richettsiae infections: ship fever； 2. Mycoplasmal pneumonia (first choice); 3. Chlamydia infections: cervicitis, urethritis, trachoma. 4. G+ and G- infections (second line choice) 5. Penicillin-resistant staphylococcus aureus.
支原体肺炎
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5. Adverse reactions
1. Local reactions: gastrointestinal tract adverse reaction；necrosis; phlebitis; 2. Secondary infections (Superinfections): a second infection superimposed on an earlier one, especially by a different microbial agent of exogenous or endogenous origin, that is resistant to the treatment being used against the first infection. 3. Effects on teeth : forbidden use for pregnant or breast-feeding woman, and children under Liver, kidney toxicity.
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6. Part 2 Chloramphenicols
Pharmacokinetics Oral absorption: rapidly and completely absorbed; Distribution: all tissues and body fluids including CNS; Excretion: metabolized and then eliminated from kidney.
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7. Antimicrobial activity, mechanism, and spectrum
1. Efficacy: quick bacteriostatic; 2. Mechanism: inhibit protein synthesis of bacteria 3. Spectrum: aerobic and anaerobic gram-positive and gram-negative organisms.
Chloramphenicol binds to the 50S ribosomal subunit at the peptidyltransferase site and inhibits the transpeptidation reaction.
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8. Clinical uses In general, it is rarely used due to toxicity.
1. Typhoid fever (first choice: third-generation cephalosporins and quinolones);
2. Bacterial meningitis (first choice: third-generation cephalosporins)
3. Anaerobic infections (alternative drugs);
4. Rickettsial diseases (first choice: tetracyclines)
5. Brucellosis (first choice: tetracyclines)
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9. Adverse reaction
1. Bone marrow suppression (1) A dose-dependent, reversible depression of erythrocyte, platelet and leucocyte formation that occurs early in treatment; (2) An idiosyncratic, non-dose related and usually fatal aplastic anemia. 2. Grey baby syndrome: circulatory collapse (neonates forbidden, daily dosage＜25mg/kg); 3. Secondary infection; 4. Hypersensitivity reactions.
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