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USMLE Antibiotics

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cebajege's version from 2016-05-16 22:52

Antibiotic Uses

DrugQuestionAnswerNumberMnemonic
Penicillin (V, G)OrganismsBACTERICIDAL - S pneumoniae/pyogenes/Actinomyces/N meningitidis/Treponema pallidum
Nafcillin, Oxacillin, dicloxacillinOrganismsS aureus (EXCEPT MRSA); PENICILLINASE RESISTANT - big R group blocks access to beta lactam ring)
Aminopenicillins (AMOXICILLIN, AMPICILLIN)OrganismsH influenzae/H. pylori/E coli/Listeria monocytogenes/Proteus mirabilis/Salmonella/Shigella (enterococci). COMBINE WITH CLAVULANIC ACID TO PROTECT AGAINST BETA LACTAMASE.
Amoxicillin > oral bioavailability

.
Ticarcillin/piperacillinOrganismsPseudomonas/gram- rods; sensitive to penicillinase, use with Beta lactamase inhibitors (clavulanic acid, sulbactam, tazobactam = CAST) Except ceftaroline covers MRSA

.
CEPHALOSPORINSOrganisms NOT coveredListeria/Atypicals (Chlamydia/Mycoplasma)/MRSA/Enterococci (=LAME)



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1st gen Cephalosporins
(cefazolin, cephalexin)
OrganismsProteus mirabilis / E coli / Klebsiella pneumoniae
Used prior surgery to prevent S. aureus wound infections



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PEcK
2nd gen Cephalosporins
(cefoxitine, cefaclor, cefuroxime - crosses BBB)
OrganismsGram + cocci, H influenzae/Enterobacter aerogenes/Neisseria/Proteus mirabilis/E coli/Klebsiella pneumoniae/Serratia marcescens




.
HEN PEcKS
3rd gen cephalosporin
Ceftriaxone
OrganismsMeningitis, gonorrhea, disseminated Lyme disease




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3rd gen cephalosporine CeftazidimeOrganismsPseudomonas



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4th gen Cephalosporins (cefepime)OrganismsPseudomonas/gram+



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5th gen Cephalosporins (ceftaroline)OrganismsBroad Gr - and + coverage, Including MRSA, does NOT cover Pseudomonas


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Carbapenems (Imipenems, meropenem, ertapenem, doripenem)OrganismsGr + cocci, Gr - rods, anaerobes. Meropenem - smaller riskof seizures, stable to dehydropeptidase I. ALWAYS administered with CILASTATIN (inh. of renal dehydropeptidase I for lower inactivation of drug by tubular cells).



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Monobactam
(Aztreonam)
OrganismsGram- rods only. Given to penicillin allergic pt and pt with renal insufficiency who can't tolerate ahminoglycosides. Synergistic with aminoglycosides. NOT cross allergic with penicillins.


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VancomycinOrganismsGr + only!!!! MRSA, S. epidermidis, enterococci, C. difficile (for pseudomembranous colitis)


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Aminoglycosides (Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin)


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OrganismsSevere gram- rod. Synergistic with Beta lactam a/b. Neomycin - bowel surgery
ChloramphenicolOrganismsMeningitis (H influenzae/N meningitidis/S pneumoniae)
Rocky Mountain Spotted fever (Ricketsia Ricketsii
Toxic but low cost


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ClindamycinOrganismsAnaerobic aspiration pneumonia/lung abscesses/oral infections (Bacteroides fragilis/Clostridium perfringns).
Invasive Group A streptococcus (osteomyelitis)


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Clindamycin treats anaerobe above diaphrahm/metronidazole below
Tetracyclines (Tetracyclin, doxycyclin, minocyclin)OrganismsBorrelia burgorferi, M pneumoniae, Rickettsia, Chlamydia. Acne Tx.


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Macrolides (Azithromycin, clarithromycin, erythromycin)OrganismsAtypical pneumonias (Mycoplasma/Chlamydia/Legionella); STDs (Chlamydia); Gram+ cocci (strep in pen allergic); B. pertussis, ureaplasma


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Oxazolidinones (Linezolid)OrganismsGram + species (inc. MRSA, VRE)


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Sulfonamides (Sulfametoxazole, sulfisoxazole, sulfadiazine)OrganismsGram+/- (Nocardia/Chlamydia)/UTI


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TrimethoprimOrganismsUTIs (Nocardia, Listeria), Shigella, Salmonella, Penumocystis jirovecii pneumonia Tx and Px, Toxoplasmosis Px

+ sulfonamides --> block of Folate synthesis

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Fluoroquinolones (Ciprofloxacin, norfloxacin, levofloxacin, ofloxacin, moxifloxacin, gemifloxacin, enoxacin)OrganismsGram- rods in UTI, GI, Pseudomonas, Neisseria, some gram+.

Travellers diarrhea

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MetronidazoleOrganismsGiardia, Entamoeba, Trichomonas, Gardnerella vaginalis, Anaerobes (Bacteroides/C difficile), H pylori (+ PPI, clarythromycin)


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IsoniazidOrganismsTx, Px- M tuberculosis
RifampinOrganismsM tuberculosis/H influenzae/Meningococcal prophyaxis
PyrazinamideOrganismsM tuberculosis
EthambutolOrganismsM tuberculosis
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Identification

DrugQuestionAnswerNumberMnemonic
PenicillinsIDPen G (IV/IM)/Pen V (oral)3N/A
Penicillinase resistant penicillinsIDOxacillin/nafcillin/dicloxacillin3N/A
AminopenicillinsIDAmpicillin/amoxicillin2N/A
AntipseudomonalsIDTicarcillin/piperacillin2N/A
1st gen CephalosporinsIDCefazolin/cephalexin2N/A
2nd gen CephalosporinsIDCefoxitin/cefaclor/cefuroxime3N/A
3rd gen CephalosporinsIDCeftriaxone/cefotaxim/ceftazidime3N/A
4th gen CephalosporinsIDCefepime1N/A
5th gen CephalosporinIDCeftaroline
30S inhibitorsIDAminoglycosides/Tetracyclines
50S inhibitorsIDChloramphenicol, clindamycin, Linezoli, Macrolides(Azythromycin, Clarithromycin, Erythromycin), Streptogramins (Dalfapristine, Quinupristine)
Beta Lactamase inhibitorsIDClavulanic Acid/Sulbactam/TazobactamCAST
MonobactamIDAztreonam
CarbapenemIDDoripenem, Ertapenem, Imipenem, Meropenem
AminoglycosidesIDGentamycin/Neomycin/Amikacin/Tobramycin/Streptomycin
TetracyclinesIDTetracycline/Doxycycline/democycline/minocycline
SulfonamidesIDSulfamethoxazole (SMX)/sulfisoxazole/sulfadiazine
FluoroquinolonesIDCipro/nor/levo/o/spar/moxi/gatifloxacins/enoxacin/nalidixic acid
MacrolidesIDArithromycin/clarithromycin/erythromycin3N/A
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Mechanisms

DrugQuestionAnswerNumberMnemonic
VancomycinMechanismInh cell wall peptidoglycan formation/binds D-ala D-ala
BACTERICIDAL

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MacrolidesMechanismInh. protein synthesis - 50S Translocation inh - binds to 23S rRNA of 50s subunit.

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Lincosamide/ClindamycinMechanismBlocks peptide translocation at 50s ribosomal subunit. BACTERIOSTATIC.

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ChloramphenicolMechanismBlocks peptidyltransferase at 50s subunit . BACTERIOSTATIC
TetracyclinesMechanismbind to 30s - no attach of aminoacyl-tRNA; Doxy - fecally excr.- + for renal failure pt.
Don't take with milk, antacids, Fe containing drugs
BACTERIOSTATIC.

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LinezolidMechanism50S Blocks initiator tRNA binding/ribosome formation
AminoglycosidesMechanismIrreversible inhibition of 30S initiation complex formation. Misreading of mRNA. Block translocation. Require O2

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SulfonamidesMechanismdihydropteroate synthase PABA to dihydropteoric acid
BACTERIOSTATIC.
BACTERICIDAL if + Trimetoprim.

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TrimethoprimMechanismdihydrofolate reductase DHF to THF)
BACTERIOSTATIC

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PyrimethamineMechanismdihydrofolate reductase DHF to THF)

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FluoroquinolonesMechanismInhibit DNA topoisomerase II (DNA gyrase). IV
BACTERICIDAL
Do not take with antacids

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MetronidazoleMechanismForms free radicals - damage DNA
BACTERICIDAL

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IsoniazidMechanismdec. synthesis of mycolic acids


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RifampinMechanismInhibits DNA dependent RNA polymerase

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PyrazinamideMechanismUncertain
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EthambutolMechanismBlock arabinosyltrasnferase/stops carbohydrate polymerization in mycobacteria
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Toxicity

DrugQuestionAnswerNumberMnemonic
PenicillinToxicityHypersensitivity/hemolytic anemia2N/A
OxacillinToxicityHypersensitivity/interstitial nephritis2N/A
NafcillinToxicityHypersensitivity/interstitial nephritis2N/A
DicloxacillinToxicityHypersensitivity/interstitial nephritis2N/A
AmpicillinToxicityHypersensitivity/rash/pseudomembranous colitis3N/A
AmoxicillinToxicityHypersensitivity/rash/pseudomembranous colitis2N/A
TicarcillinToxicityHypersensitivity1N/A
PiperacillinToxicityHypersensitivity1N/A
CephalosporinsToxicityHypersensitivity/autoimm. hem. anemia/Vit K deficiency/increases nephrotoxicity of aminoglycosides
Cross reactivity with penicillins
3N/A
AztreonamToxicityUsually nontoxic/occasional GI upset2N/A
ImipenemToxicityGI distress/skin rash/CNS toxicity (seizures)3N/A
MeropenemToxicityGI distress/skin rash/CNS toxicity (seizures)3N/A
VancomycinToxicityNephrotoxicity/Ototoxicity/Thrombophlebitis/diffuse flushing/red man sydrome5well tolerated in general/NOT many problems
AminoglycosidesToxicityNephrotoxicity/Neuromuscular blockade/Ototoxicity (+loop diuretics)/Teratogen4Mean aMINoglyocosides GNATS caNNOT kill anaerobes
TetracyclinesToxicityGI distress/discoloration of teeth/inihibition of bone growth in children/photosensitivity/contraindicated in pregnancy5N/A
MacrolidesToxicityMotility issues/Arrhythmia (long QT)/acute Cholestatic hepatitis/Rash/eOsinophilia5MACRO
ChloramphenicolToxicityAnemia/aplastic anemia/gray baby syndrome (lack UDP glucuronyl transferase)3N/A
ClindamycinToxicityPseudomembranous colitis/fever/diarrhea3N/A
SulfonamidesToxicityHypersensitivity/hemolysis in G6PD deficient/nephrotoxic/photosensitive/kernicterus in infants5N/A
TrimethoprimToxicityMegaoloblastic anemia/leukopenia/granulocytopenia3TMP (Treats Marrow Poorly)
FluoroquinolonesToxicityGI upset/superinfection/skin rash/headache/dizziness/bones (tendonitis/rupture/cramps/myalgias)/long QT7lones hurt attachment to bones
MetronidazoleToxicityDisulfiram rxn w/alcohol/headache/metallic taste3N/A
IsoniazidToxicityNeurotoxicity/hepatotoxicity/lupus3INH Injures Neurons/Hepatocytes
RifampinToxicityHepatotoxic/P450 drug interactions/Orange body fluids (nonhazardous)3
PyrazinamideToxicityHepatotoxic/hyperuricemia2N/A
EthambutolToxicityOptic neuropathy (red green colorblindness)1N/A
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Resistance

DrugQuestionAnswerNumberMnemonic
AminoglycosidesResistanceTransferases inactivate via acetylation/phosphorylation/adenylation3N/A
TetracyclinesResistanceDecreased uptake/increased efflux by plasmid encoded pumps1N/A
MacrolidesResistanceMethylation of 23S rRNA (of 50S subunit) binding site1Macrolides methylation inactivated
ChloramphenicolResistancePlasmid encoted acetyltransferase inactivates1N/A
SulfonamidesResistanceAltered target enzyme1N/A
FluoroquinolonesResistanceChromosome encoded mutation of DNA gyrase/plasmid mediated proteins bind DNA gyrase and protect/efflux pumps3N/A
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Keys to Use

DrugQuestionAnswerNumberMnemonic
AminopenicillinsKey to useAmoxicillin>Ampicillin2Oral availability of amOxacillin
Ticarcillin/piperacillinKey to useUse with clavulanic acid1N/A
3rd gen CephalosporinsKey to useWhen other Beta Lactams are resisted1N/A
ImipenemKey to useCilastatin1Kills is Lastin with cilastatin
AminoglycosidesKey to useRequire O2 for uptake/ineffective against anaerobes1Mean aMINoglyocosides GNATS caNNOT kill anaerobes
MacrolidesKey to useIncreases serum concentration of theophyllines (oral anticoagulants)1N/A
TetracyclinesKey to useDon't take w/milk/antacids/iron/pregnancy4Divalent cations inhibit absorption
DemeclocyclineKey to useADH antagonist/Diuretic in SIADH/rarely used as antibiotic1N/A
TrimethoprimKey to useCombination with sulfonamides1N/A
FluoroquinolonesKey to useDon't take with antacid1N/A
MetronidazoleKey to useTriple therapy w/PPI/clarithromycin against H pylori1N/A
IsoniazidKey to useBacterial catalase peroxidase (KatG) must convert INH to active metabolite1N/A
RifampinKey to useRapid resistance if used alone1Rifampin's 4 Rs (RNA polymerase/Revs up P450/Red-orange body fluids/Rapid resistance if used alone)
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Guidelines for Treatment and Prophylaxis

DrugQuestionAnswerNumberMnemonic
M tuberculosisProphylaxisIsoniazid1N/A
M tuberculosisTreatmentRifampin/Isoniazid/Pyrazinamide/Ethambutol4RIPE for treatment
M avium intracellulareProphylaxisAzithromycin1N/A
M avium intracellulareTreatmentAzithromycin/Rifampin/Ethambutol/Streptomycin4N/A
M leprae tuberculoidTreatmentDapsone/rifampin2N/A
M leprae lepromatousTreatmentDapsone/rifampin/clofazimine3N/A
Meningococcal infectionProphylaxisCiprofloxacin/rifampin in children2N/A
GonorrheaProphylaxisCeftriaxone1N/A
SyphilisProphylaxisBenzathine penicillin G1N/A
Recurrent UTIsProphylaxisTMP/SMX2N/A
Endocarditis w/surgical/dental proceduresProphylaxisPenicllins1N/A
Pregant women w/GBSProphylaxisAmpicillin1N/A
Streptococcal pharyngitis in child w/prior rheumatic feverProphylaxisOral penicillin1N/A
Post surgical S aureusProphylaxisCefazolin1N/A
Gonococcal/chlamydial conjunctivitis in newbornProphylaxisErythromycin ointment1N/A
MRSATreatmentVancomycin1N/A
VRETreatmentLinezolid/streptogramins (quinupristin/dalfopristin)3N/A
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To Be Avoided in Pregnancy

DrugQuestionAnswerNumberMnemonic
SulfonamidesWhy to avoid in pregnantKernicterus (bilirubin induced brain dysfunction)1N/A
AminoglycosidesWhy to avoid in pregnantOtotoxic1N/A
FluoroquinolonesWhy to avoid in pregnantCartilage damage1N/A
ClarithromycinWhy to avoid in pregnantEmbryotoxic1N/A
TetracyclinesWhy to avoid in pregnantDiscolored teeth/inhibition of bone growth2N/A
RibavirinWhy to avoid in pregnantTeratogenic1N/A
GriseofulvinWhy to avoid in pregnantTeratogenic1N/A
ChloramphenicolWhy to avoid in pregnantGray Baby1N/A
MnemonicWhy to avoid in pregnantSulfonamides/Aminoglycosides/Fluoroquinolones/Clarithromycin/Tetracyclines/Ribavirin/Griseofulvin/Chloramphenicol8SAFeChildren Take Really Good Care
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Distinctive Side Effects

Question Answer
Optic neuropathy (red green colorblindness)Ethambutol
Vitamin K deficiencyCephalosporins
Red man syndromeVancomycin
Long QTMacrolides/fluoroquinolones
Gray babyChloramphenicol
Kernicterus in infantsSulfonamides
Orange body fluidsRifampin
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USMLE Antifungals and Antivirals