Antibiotics I – Flashcards
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Antibiotics |
Antibiotics are molecules (low molecular weight metabolites) produced by microorganisms that kill other microorganisms or inhibit their growth. |
Ideal Antibiotic |
1.The drug should be low in toxicity to the host’s cells while destroying or inhibiting the disease agent (selective toxicity). 2. The drug should not induce hypersensitivity (allergy) 3.The drug should be the narrowest spectrum to treat the clinical
4.The host should not destroy, neutralize, or excrete the drug until after the drug has performed its function (pharmacokinetics). 5.The organism should not readily become resistant to the drug. |
Bactericidal vs Bacteriostatic |
Beta-lactams, vancomycin Tetracyclines, Macrolides, Anti-folates (1 used) Chloramphenicol
Aminoglycosides, Rif, Quinolones, Anti-TB drugs Anti-folates (2 used) |
Mode of Action: Cell Wall Synthesis |
Cell wall synthesis Cycloserine Vancomycin Bacitracin Penicillins Cephalosporins Monobactams Carbapenems |
Mode of Action: DNA Synthesis
|
DNA Synthesis Metronidazole (Gyrase/Topoisomerase) Quinolones |
Mode of Action: DNA directed RNA Polymerase |
DNA directed RNA Polymerase Rifampin |
Mode of Action: Protein Synthesis 30S Inhibitors |
Protein Synthesis 30S Inhibitors Tetracycline Spectinomycin Aminoglycosides (Irreversible, All other Ribosomal inhibitors reversible) |
Mode of Action: Protein Synthesis 50S Inhibitiors |
Protein Synthesis 50S Inhibitors Macrolides Chloramphenicol Clindamycin |
Mode of Action: PABA Folic Acid Metabolism |
PABA Folic Acid Metabolism Trimethoprim Sulfonamides Dapsone |
Mode of Action: Cell Membrane |
Cell Membrane Polymyxins Platensimycin
|
Mode of Action: Protein Synthesis |
Protein Synthesis Oxazolidinones |
Penicillin: Mode of Action |
|
Cephalosporins |
In contrast to penicillins Disadvantages Broader spectrum Less potent More resistant to ß-lactamases More expensive Low cross reaction with penicillins
In an average pharmacy ~40% of the antibiotics prescribed |
Cefamycins |
Similar to cephalosporins except Oxygen in ring; b-lactamases; longer half-life |
Cell Wall Biosynthesis |
Almost all antibiotics affecting cell wall biosynthesis are BACTERICIDAL and require GROWTH |
Cell Membrane |
1.Polyenes: Fungistatic (low), Fungicidal (high) Amphotericin B, Nystatin
2.Imidizoles/Azoles/Triazoles: Fungistatic Miconazole, ketoconazole, fluconazole, etc
3.Allylamines and thiocarbamates: Fungistatic Terbinafine (dermatophytes)
|
Daptomycin- A Cyclic Lipopeptide |
1.Approved September 2003 for Tx of complicated skin infections 2.First member of a new class of antibiotics; cidal; IV only 3.Mode of action is distinct from any other approved antibiotic 4.Rapidly kills Gram-positive bacteria by disrupting multiple aspects of bacterial membrane function in presence of calcium; active against MRSA/VRE 5.Emergence of resistance: rare, but 2 documented cases. |
