Antibiotics Flashcards
Which drugs block protein synthesis at 50S ribosomal subunit?
Chloramphenicol Macrolides (Erythromycin) Clindamycin Linezolid Stretogramins (Quinupristin, Dalfopristin)
Which drugs block protein synthesis at 30S ribosomal subunit?
Aminoglycosides
Tetracyclines
Mnemonic for subunits?
“Buy AT 30, CCEL (sell) at 50”
AT = 30
CCEL = 50
Which drugs are aminoglycosides?
Gentamycin Neomycin Amkiacin Tobramycin Streptomycin
*Mean GNATS canNOT kill anaerobes
MOA of aminoglycosides?
inhibits formation of initiation complex (30S) and cause misreading of mRNA.
require O2 for uptake– ineffective against anaerobes.
batericidal
Clinical use of aminoglycosides?
severe Gram - rods
synergistic with Beta-lactams
Neomycin for bowel surgery
Toxicity of Aminoglycosides?
Nephrotoxicity (when used with cephs)
Ototoxicity (when used with loop diuretics)
Teratogen
Resistance of aminoglycosides?
transferase enzymes that inactivate the drug by acetylation, phosphorylation, adenylation
Types of Tetracyclines?
Tetracycline
Doxycycline
Demeclocycline
Minocycline
MOA of tetracyclines?
binds 30S and prevents attachment of aminoacyl-tRNA
Contraindications of tetracyclines?
Doxy cannot be used in renal failure patients (fecally eliminated)
Cannot take with milk, antacids, iron-containing preps bc divalent cations inhibit gut absorption
clinical use of tetracyclines
Borrelia burgdorferi Mycoplasma pneumo Rickettsia Chlamydia (accumulates intracellularly)
Toxicity of tetracyclines
GI distress
discoloration of teeth
inhibition of bone growth in children
photosensitivity
contraindication of tetracyclines
pregnancy
resistance of tetracyclines
dec uptake into cells or inc efflux out of cell by plasmid-encoded transport pumps
Demeclocycline additional uses
ADH antagonist
Diuretic usage in SIADH
Types of macrolides?
Erythromycin
Azithromycin
Clarithromycin
MOA of macrolides?
inhibits protein synthesis by blocking translocation (macroSLIDES). binds to the 23S rRNA of the 50S ribosomal subunit
Bacteriostatic
Clinical Use of macrolides?
Atypical Pneumonias (Mycoplasma, Chlamydia, Legionella)
URIs, STDs
Gram + cocci (strep infxns in pts allergic to penicillins)
Neisseria
Toxicity of macrolides?
Prolonged QT interval (especially erythromycin)
GI discomfort (MCC noncompliance)
acute cholestatic hepatitis
eosinophilia
skin rashes
inc serum conc of theophyllines, oral anticoags
Resistance with macrolides?
methylation of 23S rRNA binding site
MOA chloramphenicol?
blocks peptide bone formation at 50S ribosome subunit.
bacteriostatic
clinical use of chloramphenicol?
Meningitis (H. flu, N. meningitidis, Strep. pneumo)
conservative use d/t toxicities.
toxicity of chloramphenicol?
Anemia (dose-dep) aplastic anermia (dose-indep) gray baby syndrome (premies bc lack liver enzyme: UDP-glycuronyl transferase)
resistance of chloramphenicol?
plasmid-encoded acetyltransferase that inactivates drug.
MOA Clindamycin?
blocks peptide bond formation at 50S ribosomal subunit
bacteriostatic
clinical use of clindamycin?
anaerobic infxns (ABOVE Diaphragm)
(Bacteriodes fragilis, Clostridium perfringens)
especially aspiration pneumo & lung abscesses
toxicity of clindamycin?
pseudomembranous colitis (C.diff overgrowth)
fever
diarrhea
Empiric tx for community-acquired penumonia in outpatient setting?
Macrolides
What is penicillin bactericidal for?
Gram + cocci, rods.
Gram - cocci
Spirochetes
Clinical use of Pencillin
Gram + orgs and syphilis.
Prototype beta-lactam ABX
types of Penicillin
Pen G = IV form
Pen V = oral form
MOA of Penicillin
1) binds penicillin-binding proteins
2) blocks transpeptidase cross-linking of peptidoglycan
3) activate autolytic enzymes
Drugs that block cell wall synthesis by inhibition of peptidoglycan cross-linking
Penicillin Methicillin Ampicillin Piperacillin Cephalosporins Aztreonam Imipenem
MOA ticarcillin, carbenicillin, piperacillin?
Same as penicillin
Extended spectrum
Penicillinase sensitive
Use w/ clavulinic acid
Resistance of ampicillin and amoxicillin?
Beta-lactamase cleaves beta-lactam ring
Amoxicillin vs ampicillin bioavailability?
AmOxicillin has greater Oral bioavailability.
Toxicity of ampicillin and amoxicillin?
Hypersensitivity rxns
Pseudo membranous colitis
Ampicillin- rash
MOA of ampicillin and amoxicillin?
Same as penicillin
Wider spectrum
Penicillinase sensitive
Combo w/ clavulinic acid to protect against beta lactamase
*AMP up with Penicillin
What are ampicillin and amoxicillin used to treat?
Haemophilus influenza E. coli Listeria monocytogenes Proteus mirabilis Salmonella Shigella enterococci
*HELPSS kill enterococci
Toxicity of methicillin, naficillin, dicloxacillin?
Hypersensitivity rxns
Methicillin- interstitial nephritis
MOA of methicillin, naficillin, dicloxacillin?
Penicillinase-resistant penicillins
(Bc bulkier R group)
Same MOA as penicillin
Narrow spectrum
What are methicillin, naficillin, and dicloxacillin used for?
Staph. aureus
(except MRSA bc altered PBP target site)
*use naf for staph
Penicillin toxicity?
Hypersensitivity Rxn
Hemolytic anemia
Penicillin resistance?
Beta- lactamase
(Cleaved beta-lactam ring)
Not penicillinase resistant
Toxicity of Aztreonam?
nontoxic
GI upset
no cross-sensitivity with Pen or Ceph
Clinical use of Aztreonam?
Gram - rods only
no activity against Gram + orgs or anaerobes
use if pen allergy or renal insufficiency and cannot tolerate aminoglycosides
MOA of Aztreonam?
Monobactam resistant to beta-lactamase.
Inhibits cell wall synthesis (binds PBP)
Synergistic with aminoglycosides
No cross-allergenicity with penicillin
Cephalosporin toxicity?
Hypersensitivity rxns
Vit K deficiency
Nephroxicity inc w/ aminoglycoside
Disulfiram-like Rxn with ETOH
Cross-hypersensitivity with penicillins
Organisms NOT covered by cephalosporins?
Listeria
Atypicals (chlamydia, mycoplasma)
MRSA
Enterococci
*LAME
Clinical use of 4th gen cephalosporins?
Cefepime
Inc activity against pseudomonas and gram + orgs
Clinical use of 3rd gen cephalosporins?
Ceftriaxone, cefotaxime, ceftazidime
Serious gram - infxn a resistant to other beta lactams
Ceftriaxone = meningitis & gonorrhea Ceftazidime = pseudomonas