ch 39 study plan - ch 39Antibiotics Part 2 Objectives 1-3...

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ch 39—Antibiotics Part 2: Objectives 1-3Minimum Inhibitory Concentraion (MIC) – a laboratory measure of the lowest concentration of drug needed to kill a certain standardized amount of bacteria. Deteremined in vitro (in the laboratory)Time-dependent Killing – amount of time the drug is above the MIC is critical for maximal bacterial kill. Concentration-Dependent Killing – achieving a drug plasma concentration that is a certain level above the MIC, even for a brief time, result is most effective bacterial kill. Objective 1 – Review the general principles of antibiotic therapy and all of the antibiotics covered previously in Chapter 38 in preparation for discussion of the following antibiotics or antibiotic classes: aminoglycosides, quinolones, clindamycin,metronidazole, nitrofurantoin, vancomycin, and miscellaneous antibiotics. Drug & its indicationaminoglycosides: gentamycinGram-negative infections treated: DZs caused by Pseudomonas species, Enterobacteriaceae family (facultatively anaerobic gram-negative rods): Escherichia coli, Proeus spp., Klebsiella spp., Serratia spp. -Treated with a suitable aminoglycoside + extended-spectrum penicillin, third-generation cephalosporin, or carbapenem.Gram-positive infections treated: DZs caused by Enterococcus spp., S. aureus, bacterial endocarditis(usually streptococcal in origin)-traditional dosages (TID) – common for treating gram-posiive infections-Aminoglycosides never used alone for Gram-positiveUsually prophylaxis in involving GI, GU tract. + Ampicillin or Vancomycin (for penicillin-allergic pts)to surgical pts with history of valvula heart DZs. Heart valves DZs prone to enterococal infectionStreptomycin is active against Mcobacterium spp. Paromomycin used to treat amebic dysentery, protozoal intestinal DZsINACTIVE against fungi, viruses, most anaerobic bacteriaHigher levels are needed for pneumoniaLower levels for urinary tract infectionIn order for aminoglycosides to be effective, the serum level needs to be at least eight times higher than the MIC.Aminoglycerides work primarily through Concentration-dependent killing.
Mechanism of action for each drug Most often used in combination with other antibiotics: Beta-lactams o Vancomycin = b/c synergic effect is greater than the sum of effectsof each drugs-When given with Beta-lactum (penicillins, cephalosporins, monobactams), beta-lactum antibiotic is given first-B/c beta-lactum break down the cell wall of the bacteria and allow the aminoglycoside to gain access to the ribosomes where they work. -Postantibiotic Effect – period of continued bacterial growth suppression that occurs afer short-term antibiotic exposure, asin once-daily aminoglycoside dosing.

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