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46 Cards in this Set
- Front
- Back
penicillin basic structure
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thiazolidine ring attached to a B-lactam ring that carries a secondary amino group
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what are penicillins most affective against
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gram-pos; gram-neg cocci; non-B-lactamase producing anaerobes
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what are antistaphlococcal penicillins most affective against
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resistant to staph B lactamases; active against staph and strep
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MIC
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minimum inhibitory unit
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what is the fxn of PBP
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removes terminal alanine in process of forming a cross-link with a nearby peptide
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where do B-lactam antibiotics bind
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to active site of PBPs
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most common mechanism of resistance to penicillins
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B-lactamase production
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methicillin resistance
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altered target PBPs
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when does resistance to impaired penetration occur with penicillins
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in gram-neg species
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excretion of penicillin
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rapidly by kidneys
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what penicillins are excreted by biliary excretion
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nafcillin; dicloxacillin and cloxacillin are kidney and biliary
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probenecid
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impairs renal tubular secretion of weak acids (like B-lactams) and can raise blood levels of these drugs
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what is generally used in place of the oral penicillin V for minor infections
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amoxicillin
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extended spectrum penicillin benefit
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greater activity than penicillin against gram-neg; enhanced ability to penetrate outer membrane
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penicillin hypersensitivity
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all are cross-reacting and cross-sensitizing
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skin rashes from ampicillin and amoxicillin
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not allergic in nature and frequently occur when prescribed inappropriately for a viral illness
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methicillin side effect
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interstitial nephritis (no longer used for this reason)
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first-generation cephalosporins action and specs
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lots of c names; active against gram-positive cocci; kidney excretion
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only first-generation cephalosporins still in general use
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cefazolin - used in surgical prophylaxis
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second generation cephalosporins
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lots more c names; large variation in activity, toxicity, etc; in general also have gram-neg coverage; renal clearance
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main uses of second generation cephalosporins
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active against H influenzae and moraxella catarrhalis - thus used to treat sinusitis, otitis, and lower resp infections
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third generation cephalosporins
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expanded gram-neg coverage, some cross blood-brain barrier; most excreted by kidney
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cefoperazone and ceftriaxone - third generation cephalosporins are excreted via
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biliary tract
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fourth generation cephalosporins
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more resistant to hydrolysis by chromosomal B lactamases; cleared by kidneys; activity against strep resistant to penicillins; enterobacter infection usefullness
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example of 4th generation cephalosporins
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cefepime
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cross-reactivity of hypersensitivity rxns btwn penicillins and cephalosporins
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5-10%
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side effect of cephalosporins with methylthiotetrazole group
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hypoprothrombinemia and bleeding disorders; administer vit K1 can prevent; also have disulfiram like rxns (avoid alcohol consumption)
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monobactams
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monocyclic B-lactam ring; aerobic gram-neg rods (pseudomonas)
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only available monobactam in US and uses
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azetreonam - penetrates CSF; renal excretion; good in penicillin allergic patients
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Beta-Lactamase inhibitors activity
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Ambler class - plasmid-encoded
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carbapenems
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end in -penem; resistant to most B lactamases (not metallo-B-lactamases); enter CSF well; renal clearance
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cilastatin
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inhibitor of renal dehydropeptidase - extends life of carbapenems
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adverse effects of carbapenems
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nausea, vomiting, diarrhea, skin rashes
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imipenem adverse rxns
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seizures in renal failure patients
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vancomycin activity
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gram-pos; binds D-ala D-ala terminus of nascent peptidoglycan pentapeptide - prevents elongation and cross-linking; renal excretion
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resistance to vancomycin
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D-ala replaced by D-lactate
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adverse rxn to vancomycin
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10% cases - minor; red neck syndrome - release of histamine
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daptomycin specs
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MOA not understood; bind cell membrane via Ca2+ dependent insertion of lipid tail; renal clearance
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why shouldn't daptomycin be used for pneumonia
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pulmonary surfactant antogonizes the drug
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fosfomycin mechanism of action
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inhibits cytoplasmic enzyme enolpyruvate transferase by covalently binding to systeine residue of active site and blocking addition of phosphoenolpyruvate to UDP-N-acetylglucosamine
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fosfomycin action
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gram pos and neg; kidney excretion; safe in pregnancy
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bacitracin specs
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cyclic peptide mixture; gram-pos; ointment use
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bacitracin mechanism
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interferes with dephosphorylation in cycling lipid carrier that transfers peptidoglycan sununits to the growing cell wall
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cycloserine specs
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gram pos and neg; TB 2nd line agent; renal excreation
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cycloserine mechanism
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analog of D-alanine and inhibits incorporation by inhibiting alanine racemase
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cycloserine toxicity
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dose-related CNS - headaches, tremors, acute psychosis, convulsions
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