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USMLE Antibiotics

Terms in this set (32)

Penicillin
MOA - Bind PBP and stop cross-linking of peptidoglycan cell wall
Use - syphilis, anthrax, gram (+), N. meningitidis,
Resistance - Beta-Lactamases
Oxacillin, Nafcillin, Dicloxacillin
MOA - Bind PBP and stop cross-linking of peptidoglycan cell wall
Use - Use Naf for Staph! Doesn't work for MRSA due to altered PBP
Beta-lactamase resistant
Ampicillin/Amoxicillin
MOA - Bind PBP and stop cross-linking of peptidoglycan cell wall
Use - HELPSS Kill Enterococcus
HiB, E. coli, Listeria, Proteus, Salmonella, Shigella, Enterococcus
Resistance - Beta-lactamases so often combined w/ Beta-lactamase inhibitors e.g. tazobactam, sulbactam and calvulonic acid.
Unasyn - Ampicillin + Sulbactam
Augmentin - Clavulonic Acid + Amoxicillin
Ticarcillin/Piperacillin
MOA - Bind PBP and stop cross-linking of peptidoglycan cell wall
Use - Extended spectrum penicillin used for pseudomonas.
Piperacillin + Tazobactam = Zosyn
Cephalosporins
MOA - Bind PBP and stop cross-linking of peptidoglycan cell wall
1st Gen - Cephalexin, Cefazolin - PEcK - Proteus, E. coli, Klebsiella and gram positive cocci
-used before surgery to prevent infxn
2nd Gen - Cefotetan, Cefuroxime, Cefoxitin, Cefaclor - HENPEcKS - HiB, Enterobacter, Neisseria, PEK, Serratia
3rd Gen - Ceftriaxone, Ceftazidime, Cefotaxime - Serious gram (-) infxn
Ceftriaxone for meningitis and gonorrhea
Ceftazidime for Pseudomonas
4th Gen - Cefepime - increased activity against gram positives and pseudomonas
AE - Low cross-reactivity w/ penicillin but still avoided if possible
May cause Vit K deficiency
Organisms not covered by cephalosporins?
CAMEL
Chlamydia
Atypical pneumonia - mycoplasma
MRSA
Enterococci
Listeria
Aztreonam
MOA - Prevents peptidoglycan corsslinking by binding to PBP3 which is only in gram (-) aerobes
Use - Gram (-) rods only. commonly used in penicillin allergy patients w/ renal insufficiency (can't tolerate aminoglycosides)
No cross reactivity w/ penicillin
Carbapenems - Imipenem, Meropenem
MOA - Bind PBP and stop cross-linking of peptidoglycan cell wall
Use - BROAD RANGE - used as a last resort to help prevent resistance development/bad AE.
Imipenem must be given w/ cilastatin in order to decrease rapid renal clearance
AE - Imipenem lowers seizure threshold. Both cause GI distress and rash
Vancomycin
MOA - Inhibits D-ala D-ala portion of cell-wall precursors
Use - Gram positives only, for multidrug resistant staph, enterococci and C. diff
No oral absorption --> MOA of C. diff clearance
AE - Red Man Syndrome if flushed too quickly
Can be nephrotoxic or ototoxic
What antibiotics inhibit the 30s ribosome?
Aminoglycosides
Tetracyclines
What antibiotics inhibit the 50s ribosome?
Clindamycin
Chloramphenicol
Erythromycin (macrolides)
Linezolid
Aminoglycosides
STANG - Streptomycin, Tobramycin, Amikacin, Neomycin and Gentamicin
MOA - inhibit initiation complex of 30S ribosome, require Oxygen for entrance into cell
Use - Severe gram(-) rod infections. Synergistic w/ beta-lactams
AE - Nephrotoxic, Ototoxic, Neuromuscular blockade
Ototoxicity enhanced w/ combined w/ Lasix
Teratogen
Tetracyclines
Tetracycline, Minocycline, Doxycycline, Democlocycline
MOA - inhibit attachment of charged tRNA to 30s Ribosome. Good w/ intracellular bugs
Use - Rickettsia, Borrelia, Mycoplasma, Chlamydia
Doxy can be used in renal failure
AE - Not for pregnancy - Discolored teeth and inhibition of bone growth.
Democlocycline - ADH antagonist for SIADH.
Divalent cations (milk, antacids) inhibit absorption
Macrolides
MACE - Azithromycine, Clarithromycin, Erythromycin
MOA - Block translocation of the 50s ribosome
Use - Gram(+) cocci, Atypical pneumonais (mycoplasma, chlamydia, legionella), chlamydia
AE - MACRO - motility issue, arrhythmia (Long QT), cholestatic hepatitis, rash, eOsinophilia
Azithromycin for chlamydia because you can give them just one dose
clarithromycin is embryotoxic
CYP 450 inhibitors
Chloramphenicol
MOA - inhibits peptidyltransferase of 50s ribosome
Use - Meningitis in 3rd world
AE - anemia, gray baby syndrome
Clindamycin
MOA - blocks transpeptidation at 50s ribosome
Use - Anaerobic infections above the diaphragm
AE - MCC c. diff colitis,
Sulfonamides (SMX)
MOA - inhibits dihydropteroate synthase to inhibit purine synthesis
Use - gram(+), gram (-), Nocardia, Chlamydia, UTI, PCP
AE - hemolysis in G6PD patients, kernicterus in infants, displaces other drugs from warfarin, nephrotoxic, hypersensitivity rxn
Trimethoprim (TMP)
MOA - Inhibits dihydrofolate reductase in purine synthesis
Use - TMP-SMX used for UTI, Shigella, Salmonella, PCP
AE - TMP Treats Marrow Poorly - megaloblastic anemia, leukopenia, granulocytopenia
Fluoroquinolones
Ciprofloxacin et al
MOA - inhibit DNA gyrase
Use - Gram(-) rods of urinary and GI tract, legionella, neisseria
AE - not for pregnancy, GI, increase seizure risk, tendonitis and achilles tendon rupture, prolonged QT
Can't take w/ divalent cations due to impaired absorption
Metronidazole
MOA - forms free radials to damage DNA. Ferrodoxin dependent
Use - GET GAP - Giardia, E. histolytica, Trichomonas, Gardinella, Anaerobes, H. pylori
Use for anaerobes below the diaphragm
AE - Disulfiram like reaction w/ alcohol, metallic taste, teratogen
Prophylaxis for M. tb?
Isoniazid
Prophylaxis for M. avium-intracellulare
Azithromycin
Course for active Tb?
RIPE
Rifampin
Isoniazid
Pyrazinamide
Ethambutol
Course for Leprosy?
Dapsone + Rifampin + Clofazimine
Isoniazid (INH)
MOA - inhibit synthesis of mycolic acids for cell wall. Needs bacterial KatG to become active
Use - Tb. Never use alone during active infection because resistance will develop
AE - Isonizaid injures Neurons and Hepatocytes
Hepatitis, B6 deficiency--> neural sx, SLE exascerbation
Rifampin
MOA - inhibits mRNA synthesis by inhibiting DNA-dependent RNA polymerase
Use - Tb course. leprosy. meningitis prophylaxis in kids.
AE - orange body fluids, p-450 inducer
Pyrazinamide
MOA - unknown, able to get inside cells
Use - Tb
AE - hepatotoxic
Ethambutol
MOA - inhibits carbohydrate polymerization of Tb cell wall
Use - Tb
AE - Optic neuropathy -> R/G color blindness
Antibiotics that should be avoided in pregnancy?
GRAFTS CC
Sulfonylureas - kernicterus
Aminoglycosides - ototoxicity
Fluoroquinolones - cartilage/tendon damge
Clarithromycin - embryotoxic
Tetracyclines - teeth and bone deformities
Ribavirin - teratogen
Griseofulvin - teratogen
Chloramphenicol - Gray baby
Prophylaxis for PCP pneumonia in HIV patients?
TMP-SMX
Prophylaxis for Toxoplasma gondii in HIV patients?
TMP-SMX
Prophylaxis for histoplasma capsulatum in HIV patients?
Itraconazole
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