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•Agents given to prevent infection rather than to treat an established infection•Surgery•Bacterial endocarditis•Neutropenia•Other indications
SPECTRUM OF ACTIVITYNarrow spectrum•Effective against limited number of organisms•Unlikely to disrupt normal floraBroad spectrum•Effective against multiple organisms from more than a single class•Active against a wide array of microbes.•Higher risk of resistance•↑ superinfections•Caused by drug-resistant microbes•Usually bacterial or viral
ANTIBIOTIC OVERVIEW•Bacteriostatic•Only suppress bacteria growth•Rely on functioning immune system•Clindamycin•Macrolides•Sulfonamides•Tetracycline•Trimethoprim•Bactericidal•Kill bacteria regardless of immune system•Aminoglycosides* •Fluoroquinolones*•Metronidazole*•Linezolid•Rifampin•Vancomycin•Beta-Lactams* These have both bacteriostatic and bactericidal activity
TIME VS CONCENTRATION KILLINGConcentration-Dependent Killing (e.g. aminoglycosides & fluoroquinolones)•The rate & extent of killing increases as the peak drug concentration increases•These drugs exhibit a ”post-antibiotic effect” or persistent suppression of bacterial growth after limited exposure to an antibiotic.•A need for bacteria to synthesize new proteins before growth can continueTime-Dependent Killing(e.g. β-lactams, vancomycin, macrolides, linezolid)•Bactericidal activity continues as long as the plasma concentration is greater than the minimum bactericidal concentration.•The concentration of these drugs should be maintained above the MIC for the entire time interval between repetitive doses.
PENICILLINS•Active against a variety of bacteria•Direct toxicity: low•Principal adverse effect: allergic reaction •Beta-lactam ring in their structure•Beta-lactam family: also includes cephalosporins, aztreonam, imipenem, meropenem, and ertapenem
PENICILLIN (PCN)•Mechanism of action•Disrupts synthesis of cell wall•Bactericidal activity & Time Dependent Killing•Pharmacokinetics•Absorption is variable•Ampicillin less oral bioavailability than amoxicillin•Renal adjust if necessary•ADR – Rash, anaphylaxis(cross reactivity - cephalosporin), hyperkalemia (aqueous PCN G)•Pregnancy Category B•Administration•Take on empty stomach (increase absorption)•Full glass of water (Except amoxicillin)•Alternative for g(+) infection:•Cephalosporin•Macrolides•Clindamycin
MECHANISMS OF BACTERIAL RESISTANCE•Three factors•Inability of penicillins to reach their targets•Inactivation of penicillins by bacterial enzymes•Production of penicillin-binding proteins (PBPs) that have a low affinity for penicillins
PENICILLINASES•Beta-lactamases•Enzymes that render penicillin inactive•Bacteria can produce a large variety of these enzymes specific for penicillins (and other beta-lactam antibiotics)