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Antibacterial agents
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49
Medical
Graduate
04/05/2008

Additional Medical Flashcards

 


 

Cards

Term

 

 

 

Inhibition of cell wall synthesis

Definition

Penicillins, cephalosporins, imipenem/meropenem, aztreonam, vancomycin

Term

 

 

 

Inhibition of bacterial protein synthesis

Definition
Aminoglycosides, chloramphenicol, macrolides, tetracyclines, streptogramins, linezolid
Term

 

 

 

Inhibtion of nucleic synthesis

Definition
Fluoroquinolones, rifampin
Term

 

 

 

Inhibition of folic acid synthesis

Definition
Sulfonamindes, trimethoprim, pyrimethamine
Term

 

 

 

Penicillin & cephalosporins resistance mechanisms

Definition
produces beta-lactamases that cleave the beta lactam ring structure, change the PCN-binding proteins, change in porins
Term

 

 

 

Aminoglycosides resistance

Definition

Drugs that bacteria develop resistance to (gentamicin, streptomycin, amikacin)

 

Forms enzymes that inactivate drugs via conjugation rxns that trasfer acetyl, phosphoryl etc. groups

Term

 

 

 

Macrolides and clindamycin resistance 

Definition

Drugs erythromycin, azithromycin, clarithromycin etc.

 

Forms methyltransferases that alter drug binding sites on the 50S ribosomal subunit, or active transport of the drug out of cells

Term

 

 

 

Tetracyclines resistance

Definition
Increased activity of transport systems that "pump" drugs out of the cell
Term

 

 

 

Sulfonamides resistance

Definition
Change in sensitivity to inhibition of target enzyme, increased formation of of PABA, use of exogenous folic acid
Term

 

 

 

Fluoroquinolones

Definition
Change in sensitivity to inhibition of target enzymes (topioisomerase II); increased activity of transport systems that promote drug efflux
Term

 

 

 

Chloramphenicol resistance

Definition
Formation of inactivating acetyltransferases
Term

 

 

 

Penicillins

Definition

MOA: interact w/ cytoplasmic membrane binding proteins to inhibit transpeptidation rxns involving the bacterial cell wall synthesis

 

Elimination: most via active tubular secretion in kidney, nafcillin, oxacillin eliminated via bile, benzathine pcn G eliminated via repository form

 

SE: hypersensitivity can be any of the type I-IV rxns  

 

 

Term

 

 

 

Narrow spectrum PCN's

Definition

Penicillin G and V

 

Spectrum: gram (+) cocci (strep/penumo/meningo) + Treponema pallidum (G is DOC for syphilis)

Term

 

 

 

Very narrow spectrum PCN's

Definition

nafcillin, methicillin, oxacillin

 

Spectrum: known or suspected staphylococci (NOT MRSA)

Term

 

 

 

broad spectrum PCN's

Definition

beta-lactamase sensitive

 

Ampicillin & Amoxicillin

 

Spectrum: gram + cocci (not staph), E.coli, H, influenzae, Listeria monocytogenes (DOC ampicillin) Borrelia burgdorferi, H.pylori (amoxicillin)

 

Activity enhaced if used w/ clavulanic acid which are inhibitors of beta lactamase

 

Synergy w/ aminoglycosides (gentamicin) against enterococcal species

Term

 

 

 

Extended spectrum PCN's

Definition

Ticarcillin, piperacillin, azlocillin

 

Spectrum: everything plus gram (-) rods like Pseudomonas aeruginosa

 

Enhanced activity if used w/ beta-lactamase inhibitors like clavulanic acid and sulbactam

 

Synergy w/ aminoglycosides against Pseudomonas

Term

 

 

 

Two drug bugs

Definition

Pseudomonas

 

Listeria

 

Enterococcus

Term

 

 

 

Cephalosporins

Definition

MOA: interact w/ cytoplasmic membrane-binding proteins to inhibit transpeptidation rxns w/in bacterial cell walls

 

Elimination: via active tubular secretion blocked by probenecid, ceftriaxone is eliminated via bile

 

SE: hypersensitivity (rashes/drug fever),

disulfiram-like rxn (cefotetan, cefoperazone, cefamandole)

hypoprothrombinemia (def. of factor II)  

Term

 

 

 

Organisms not covered by cephalosporins

Definition

Listeria monocytogenes (amp + gent)

Atypicals (chlamydia, mycoplasma)

MRSA (vancomycin)

Enterococci (amp +gent)

Term

 

 

 

Narrow spectrum cephalosporins (1st gen.)

Definition

cefazolin, cephalexin

 

Spectrum: gram + cocci, Proteus, E.coli, Klebsiella pneumoniae

 

Common in surgical prophylaxis, DO NOT enter CNS

Term

 

 

 

Broad spectrum cephalosprorins (2nd gen.)

Definition

cefotetan, cefaclor, cefuroxime

 

Spectrum: increasing gram (-) coverage, some anaerobes (Actinomyces, bacteriodes, clostridium)

Term

 

 

 

Very broad spectrum cephalosporins (3rd gen.)

Definition

Ceftriaxone, Cefotaxime, Cefdinir, Cefixime

 

Spectrum: Less gram (+) more gram (-) cocci & rods

 

Most enter the CNS

Empiric management of meningitis and sepsis 

Term

 

 

 

very broad spectrum cephalosporins (4th gen.)

Definition

Cefepime

 

Widest spectrum for mostly gram (-) cocci/rods

 

Resistant to most beta-lactamases

 

Enters the CNS

Term

 

 

 

Imipenem, Meropenem, Ertapenem

Definition

MOA: interact w/ cytoplasmic membrane-binding proteins to inhibit transpeptidation rxns w/in the bacterial cell wall (resistant to beta-lactamases)

 

Spectrum: broadest we have! use for empiric tx

 

Imipenem is given w/ cilastatin which inhibits its rapid metabolism by renal dehydropeptidase

 

SE: GI distress, drug fever, CNS effects

Term

 

 

 

Aztreonam

Definition

MOA: interact w/ cytoplasmic mebrane-binding proteins to inhibit transpeptidation of bacterial cell wall synthesis (resistant to beta-lactamases)

 

Spectrum: IV drug mainly active against gram (-) rods, doesn't kill any gram (+)

Term

 

 

 

Vancomycin

Definition

MOA: binds to the D-ala-D-ala muramyl pentapeptide to sterically hinder the transglycosylation rxns involved in peptidoglycan chains

 

Spectrum: only gram +'s, Enterococci  

DOC: for nosocomial MRSA

used as a backup drug for C. difficile

 

Enterococcal resistance involves change in the muramyl pentapeptide target via changing the D-ala to a D-lactate

 

Given IV and orally (not absorbed so good for colitis)

 

SE: "red man syndrome" from histamine release, otoxicity, nephrotoxicity

Term

 

 

 

Aminoglycosides (MOA)

Definition

30s

 

Inhibits formation of initiation complex, via blocking associaiton of 50s ribosomal subunit w/ mRNA-30s, causes misreading of code, may even incorporate wrong amino acid (if so = bacteriocidal)

Term

 

 

 

Linezolid (MOA) 

Definition

50s

 

Inhibits the formation of the initiation complex by blocking the association of 50s ribosomal subunit w/ mRNA-30s

 

Term

 

 

 

Tetracyclines (MOA)

Definition

30s

 

Block the attachment of aminoacyl tRNA to the acceptor site = tRNA specific for each AA is not allowed to enter site

Term

 

 

 

Dalfopristin/quinupristin (MOA) 

Definition

50s

 

block the attachment of aminoacyl tRNA to acceptor site  

Term

 

 

 

Chloramphenicol (MOA) 

Definition

50s, bacteriostatic

 

Inhibits the activity of peptidyltransferase (can't form peptide bond w/ elongating chain) 

Term

 

 

 

Macrolides & clindamycin (MOA)

Definition

50s, bacteriostatic

 

Inhibits translocation of peptidyl-tRNA from acceptor to donor site

Term

 

 

 

Aminoglycosides

Definition

gentamicin, tobramycin, amikacin, streptomycin

 

Accumulated intracellularly via an O2-dependent uptake (so anaerobes are innately resistant), spectrum = gram (-) rods only

 

Streptomycin: used in TB and is DOC for bubonic plague & tularemia

 

Renal elimination so adjust dose in renal dysfunction

 

SE: nephrotoxicity (usu reversible but enhanced by vancomycin, amphotericin B, cisplatin, and cyclosporine), ototoxicity (enhanced by loop diuretics)

Term

 

 

 

Tetracyclines

Definition

doxycycline, minocycline, demeclocycline

 

30s, bacteriostatic

 

Spectrum: "broad" including chlamydial, mycoplasmal species, H.pylori, Rickettsia, Borrelia burgdorferi, Brucella, Vibrio

 

doxycyline: more activity overall, good for prostatitis b/c reaches high levels there

minocycline: concentrates in saliva/tears

demeclocycline: used in SIADH blocks ADH receptor function in collecting ducts (receptors aka V2)

 

Elimination: kidney except doxy via liver

chelators: bind divalent cations (Ca2+, Mg2+, Fe2+, Al3+) which decrease their absorption so becareful w/ antacids

 

SE: Tooth enamel discoloration & dec. bone growth in children (DON'T use)

Phototoxicity

 

 

Term

 

 

 

Chloramphenicol

Definition

50s, bacteriostatic

 

Spectrum: wide, used as back up drug for Salmonella typhi, B. fragilis, Rickettsia

 

Metabolized by hepatic glucuronidation so dec. dose in liver failure/neonates, also inhibits CYP450

 

SE: dose-dependent bone marrow supression, "gray baby syndrome" in neonates (b/c can't glucuronidate)

Term

 

 

 

Macrolides

Definition

erythromycin, azithromycin, clarithromycin

 

50s, broad spectrum, often used in community acquired pneumonia 

 

erythromycin: gram + cocci, atypicals (chlamydia, mycloplasma), legionella, Campylobacter jejuni)

liver metabolism, CYP450 inhibitor

azithromycin: above + more active in respiratory infxns Mycobacterium avium

Excreted by kidney, safer in pregnancy

clarithromycin: greater activity against M. avium and H. pylori

liver metabolism, CYP450 inhibitor

 

SE: stimulate motilin receptor & cause GI distress, reversible deafness a high doses, erythromycin estolate causes cholestasis, jaundice

Term

 

 

 

Clindamycin

Definition

50s, not a macrolide

 

Spectrum: "narrow" gram + cocci (no MRSA), anaerobes including B. fragilis, toxoplasmosis

 

Concentrates in bone so has value in osteomyelitis

 

1st known drug to cause pseudomembranous colitis (caused by C. difficile)

Term

 

 

 

Linezolid

Definition

50s, inhibits the formation of the initiation complex in bacterial translation systems by preventing formation of the complex

 

Spectrum: tx of vancomycin resistant Staph & Enterococci, and drug-resistant pneumococci

 

SE: bone marrow supression (thrombocytopenia- dec. platelets)

Term

 

 

 

Quinupristin-Dalfopristin

Definition

MOA: streptogramins that act in concert via several mechanisms (prevent interaction of amino-acyl-tRNA w/ acceptor site and stimulate dissociation from ternary complex & block the extrusion of a completed polypeptide)

 

Spectrum: parenteral for VRSA & VRE, and other drug-resistant gram + cocci  

Term

 

 

 

Sulfonamides, trimethoprim & pyrimethamine

Definition

MOA: folic acid synthesis inhibitors

sulfonamides inhibit the bacterial enzyme dihydropteroate synthetase and trimethoprim & pyrimethamine inhibit the human & bacterial enzyme dihydrofolate reductase

 

Sulfonamindes alone =limited use

Sulfasalazine = prodrug in UC and RA

Ag sulfadiazine = used topically in burns

TMP-SMX = DOC in nocarida, mycobacteria, gram (-) infxns (E.coli, salmonella, shigella, H.flu) gram (+), fungus (pneumocystis jiroveci), protozoa (toxoplasma gondii - use sulfadiazine + pyrimethamine)

 

Elimination: sulfonamides are hepatically acetylated, highly protein bound causes kernicterus in neonates (don't use in 3rd trimester)

 

SE:

Sulfonamides = hypersensitivity (SJS), phototoxicity, hemolysis in G6PD deficiency

Trimethoprim or Pyrimethamine = bone marrow supression (anemias anti-folate)

Term

 

 

 

Drugs that have sulfonamides w/in watch for allergies

Definition

1. carbonic anhydrase inhibitors

2. thiazides

3. loops

4. sulfonylureas

5. celecoxib, valdecoxib

Term

 

 

 

Stevens Johnson Syndrome

Definition

1. erythema multiforme

2. hemorrhagic crusts of lips and oral mucosa

3. MC in kids

Term

 

 

 

Quinolones

Definition

Norfloxacin, ciprofloxacin, ofloxacin, other oxacins

 

MOA: inhibit topoisomerase II (DNA gyrase) responsible for separation of replicated DNA during cell division (ie: inhibits DNA synthesis)

 

Spectrum: great gram (-) coverage but not 1st line

 

Fe2+, Ca2+ limit their absorption (chelators), eliminated via kiney

 

SE: Phototoxicity, tendonitis/tendon rupture w/ long term use, increase the QT interval (so risk of torsades)

Term

 

 

 

Metronidazole

Definition

unclassified ATBX, may produce free radicals?

 

GET BaC on the Metro

Spectrum: giardia, entamoeba, trichomonas (protozoal), bacteroides, clostridium (bacterial) DOC for pseudomembranous colitis SE: metallic taste, stomatitis, cystitis, disulfram-like effect
Term

 

 

 

H.pylori regimins

Definition

"BMT" regimin = bismuth, metronidazole, and tetracycline

 

OR

 

Clarithromycin, amoxicillin, omeprazole

Term

 

 

 

Isoniazid

Definition

one of the drugs used for TB, & prophylaxis

 

MOA: inhibits mycolic acid synthesis, but is a prodrug

 

Resistance: comes via deletions in the katG gene that encodes the catalase needed for INH bioactivation

 

SE: Hepatitis, peripheral neuritis, sideroblastic anemia, hemolysis in G6PD def., SLE in slow acetylators

Term

 

 

 

Rifampin

Definition

used in TB tx

 

MOA: inhibits DNA-dependent RNA polymerase (nucleic acid synthesis inhibitor)

 

SE: hepatitis, induction of CYP450, red-orange metabolites in sweat, urine, tears 

Term

 

 

 

Ethambutol

Definition

TB tx. regimin

 

MOA: inhibits synthesis of arabingalactan (cell wall component)

 

SE: dose-dependent retrobulbar neuritis --> dec. visual acuity and red-green discrimination

Term

 

 

 

Pyrazinamide

Definition

TB tx regimin

 

MOA: unkown

 

SE: hepatitis, polyarthralgia, myalgia, rash, hyperuricemia (GOUT!!!), phototoxicity, inc. porphyrin synthesis

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