Agents given to prevent infection rather than to treat an established infection

Agents given to prevent infection rather than to

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Agents given to prevent infection rather than to treat an established infection SurgeryBacterial endocarditisNeutropeniaOther indications
SPECTRUM OF ACTIVITY Narrow spectrum Effective against limited number of organisms Unlikely to disrupt normal flora Broad 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 KILLING Concentration-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 continue Time-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.
Bactericidal Bactericidal Bacteriostatic Bacteriostatic Bactericidal
Copyright © 2015 Wolters Kluwer • All Rights Reserved CHAPTER 37 Figure 37.10
CELL WALL INHIBITORS
PENICILLINS Active against a variety of bacteriaDirect toxicity: lowPrincipal adverse effect: allergic reaction Beta-lactam ring in their structureBeta-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)
CLASSIFICATION OF PENICILLINS

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