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38 Cards in this Set
- Front
- Back
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Mechanism of action |
Inhibit transpeptidase - prevents cell wall formation - lysis and death |
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Time dependent |
Not much post antibiotic effect |
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Distribution |
Good in ECF, not so good in ICF |
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Excluded from |
CSF and aqueous humour |
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Metabolism |
None, active drug excreted through kidney |
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Excretion through kidney |
Glomerular filtration and active tubular secretion |
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Benzathene vs procaine penicillin G |
Benzathene - 48 hours vs 24 hours - less soluble salt |
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Broad spectrum penicillins ampicillin and amoxicillin |
Gram positive and gram negative, acid stable, beta-lactamase susceptible |
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Antipseudomonal penicillins carbenicillin, ticarcillin |
Gp and Gn, beta-lactamase susceptible |
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Oral bioavailability of ampicillin and amoxicillin |
Amoxicillin more bioavailable orally - 60-70% compared to 20-40% |
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Clavulanate |
Helps to inhibit beta-lactamase produced by bacteria (e.g. synulox) |
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Sodium salt |
Makes soluble so IV administration |
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Trihydrate salt |
12-24 hours Oral or injectable |
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Depot preparations - oily vehicle |
longer acting |
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Ticarcillin, carbenicillin |
Dicarboxylic acid derivatives Beta-lactamase susceptible - apply with beta lactamase resistant thing Acid labile - not orally bioavailable In combo with AG - synergy |
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Piperacillin |
Ureidopenicillin |
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Beta lactamase inhibitors |
Clavulanate - most routinely used tazobactam Sulbactam |
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Action |
Bind irreversibly to beta-lactamase enzyme and they themselves are destroyed Also antibacterial slightly |
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Penicillin toxicity |
Anaphylaxis or mild hypersensitivity Toxicity associated with salt formation Small herbivorous animals - disturb GI flora - fatal clostridial colitis |
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Interactions of penicillins |
Synergistic with aminoglycosides - damage to cell wall, improves AG access Synergistic beta-lactamase inhibitors - clavulanic acid Synergistic within penicillin family - cloxacillin - anti-staph |
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Difference between cephalosporins and penicillins |
More resistant to beta-lactamase |
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First generation |
Good Gram-pos. and anaerobes Moderate Gram-neg. Orally bioavailable e.g. cefradroxil, cephalexin |
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Second generation |
Better G-neg. E. coli, Klebsiella, Proteus e.g. cefuroxime |
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Third generation |
Reduced G.-pos. Excellent G.-neg. - enterobacteriacae, pseudomonas e.g. ceftiofur |
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Ceftiofur |
Highly protein bound Rapidly metabolised to desfuroylceftiofur - active anti-microbial (unusual) Doesn't readily cross mammary gland and into milk - 0 withdrawal period |
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Fourth generation |
e.g. cefquinome Superior in G.-neg. activity Third and fourth gen. less orally bioavailable |
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Structure |
Beta-lactam ring Dihydrothiazine ring 3D structure protects b-l ring |
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Mechanism of action |
Same as penicillins Crosslinking of peptidoglycan Bactericidal - rapidly multiplying bacteria Time-dependent anti-microbials |
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Distribution |
Good to ECF Poor to intracells High concs in urine and bile Excluded from prostate, CSF, eye |
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Half life |
Short, 6-8 hour dosing required |
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Metabolism |
None usually, renal excretion |
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Renal excretion |
Glomerular filtration and active tubular secretion |
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Exceptions |
De-acetylated in liver - cephalothin and ceftiofur - active metabolites |
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Companion animals |
Cephalexin Cefovexin - parenteral administration as 3rd gen., long half life, protein bound, dose every 14 days |
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Farm animals |
Ceftiofur - 3rd gen., highly protein bound, metabolised to active metabolite - desfuroylceftiofur, no milk withdrawal
Cefquinome - 4th gen. |
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Carbapenem and monobactam |
Not licensed in vet med - safeguarded Very broad spectrum - last resort in human medicine - very resistant organisms |
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Carbapenem e.g. |
Imipenin - administered with cilastatin - prevents metabolism of imipenin to toxic compound - by renal hydrolysis |
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Monobactam e.g. |
Aztreonam |
