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46 Cards in this Set
- Front
- Back
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What are the sub classes of beta lactams |
Penicillins Cephalosporins Monobactams Carbapenems |
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Why are beta lactams called as such |
They have a beta lactam ring as part of their structure |
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How do beta lactams work? |
Inhibit transpeptidase enzymes (PBPs) Disrupt cross linking of bacterial cell wall More effective for gram positive as they have a thicker peptidoglycan cell wall layer Lyses peptidoglycan wall in growing cells - bactericidal |
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What determines beta lactam activity |
Penicillin binding proteins present Ability to penetrate lipopolysacharide layer Resistance Amount of peptidoglycan present (G+/G-) |
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What is beta lactamase |
Enzyme that cleaves the beta lactam ring |
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What gram positive bacteria produce beta lactamase |
staphylococci - exogenously released and plasmid mediated |
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What gram negative bacteria produce beta lactamase |
Many - e.coli, klebsiella, pseudomonas (enterobacteriaceae) Chromosomally mediated in periplasmic location |
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Pka of penicillins |
2.7 |
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Volume of distribution of penicillins |
0.5-1.2h |
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Where are penicillins distributed and why |
Predominantly ionised at plasma pH Penetration is enhanced by inflammation (becomes more acidic) Excluded from CSF, aqueous humour Predominantly in ECF - cannot enter cells (too ionised) |
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How are penicillins excreted and why |
Glomerular filtration and tubular secretion
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Why are penicillins good in UTI |
Due to being excreted at the site of the kidney |
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Do penicillins have postantibiotic effect |
no/not much |
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What are the 3 groups of narrow spectrum peniciliines |
Gram positive only, acid labile, beta lactamase susceptible Gram positive only, acid stable, beta lactamase susceptible Gram positive only, acid and beta lactamase stable |
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What type of penicillin is penicillin G |
Gram positive only, acid labile, beta lactamase susceptible |
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What type of penicillin is penicillin V |
Gram positive only, acid stable, beta lactamase susceptible |
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What type of penicillin are cloxaxillins or naficillin |
Gram positive only, acid and beta lactamase stable |
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What gram positives are penicillin g and v active against |
Staph aureus Beta haemolytic strep Corynebacterium Erysipelothrix Bacillus |
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What gram negatives are penicillin g and v active against |
Haemophilus Pasteurella Actinobacillus |
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Wha anaerobes are penicillin g and v active against? |
Clostridium and fusobacterium |
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Limitations of penicillin G |
Unstable in gastric acid Beta lactamase susceptible Relatively poor against G- bacteria |
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How do we administer narrow spectrum penicillins |
Range of benzylpenicillin salts - that vary in solubility and duration
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What type of bacteria are beta lactamase resistant penicillins resitant to |
Gram positive not gram negative lactamase |
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Duration of crystapen and type of salt |
4h - sodium salt |
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Affect of solubility on duration of action |
Less soluble lasts longer |
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Duration of pricaine benzylpenicillin |
24h |
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Duration of trihydrate? |
12-24h |
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How do we administer aminopenicillins |
Sodium IV Soluble |
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What is the structure of the cephalosporins |
Beta lactam and dihydrothiazine ring Act in the same way as penicillins |
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Pharmacokinetics of cephalosporins |
Low Vd Organic acids Urinary/billiary excretion
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What are the 1st generation cephalosporins excluded from |
Excluded from prostate and aqueous |
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What cephalopsorins have active metabolites that require de-acetylation before urinary exc |
Cephalothin (1) Ceftiofluor |
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How does bioavailability change from one generation to the next |
Decreases |
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First generation cephalosporins |
Cephradoxil Cephacetrile Cephalexin Cehalotin |
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Spectrum of the 1st generations |
Good against penicillinase producing G+ Moderate against G- |
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What changes occur over the cephalosporins |
Increased G- activity Reduced G+ activity Reduced bioavailability |
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Nature of cephalosporins |
Bactericidal Time dependant Act same as pencicillins |
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Second generation cephalosporins |
Cefuroxine |
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Third generation cephalosporins |
Cefoperazone Cefovexin Ceftiofluor |
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Properties of cefovexin |
Small animal Long acting Very PPB Parenteral admin |
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Properties of ceftiofluor |
Partitioned away from milk Binds to acute phase proteins Large animals Hepatic metabolism - active |
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Fourth generation |
Cefquinone |
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Properties of cefquinone |
Broad spectrum Not destroyed by Beta lactamase producing Klebsiella/Pseudomonas Used in food animals |
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Properties of third generation cephalosporins |
Reduced G+ Improved G- |
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What can you use in addition to beta lactams |
cilastatin to reduce renal hydrolydid |
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What beta lactams are reserved for human use and whyq |
Carbapenam Monobactam Beta lactamase stable - want to conserve |
