First Aid USMLE Step 1: Pharmacology
(Complete)
Penicillin G (IV and IM)
Penicillin M (oral) Ans- *MOA:*
*β-lactam*: a structural analog of D-ala-D-ala (a normal component of cell walls) which
binds and inactivates bacterial transpeptidases (penicillin-binding protein, PBPs) to
block peptidoglycan cross linking
*Clinical use:*
Bactericidal for Gram-⊕ cocci/rods, Gram-⊖ cocci (Neisseria), and spirochetes
Mostly used for Gram-⊕ organisms (S. pneumoniae, S. pyogenes, Actinomyces). Also
used for Gram-⊖ cocci (mainly N. meningitidis) and spirochetes (namely T. pallidum).
Bactericidal for Gram-⊕ cocci, Gram-⊕ rods, Gram-⊖ cocci, and spirochetes.
Penicillinase sensitive.
*Toxicity:*
Hypersensitivity reactions (type II), hemolytic anemia
*MOR:*
Penicilinase (a type of β-lactamase) in bacteria cleaves
Oxacillin
Nafcillin
Dicloxacillin Ans- Penicillinase-resistant penicillins
*MOA:*
Same as penicillin.
*Narrow spectrum*; penicillinase resistant because bulky R group blocks access of β-
lactamase to β-lactam ring.
*Clinical use:*
Bactericidal, narrow spectrum: *S. aureus* (except MRSA; resistant due to altered
penicillin-binding protein target site).
*Toxicity:*
Hypersensitivity reactions (type II), interstitial nephritis
"Use *naf* (*naf*cillin) for staph." Nafcillin has penetration to CNS
Aminopenicillins:
,Ampicillin
Amoxicillin Ans- Penicillinase-sensitive penicillins
*MOA:*
Same as penicillin.
Wider spectrum with better activity against Gram-⊖ bugs; penicillinase sensitive.
Administer with clavulanic acid to protect against destruction by β-lactamase.
*Clinical use:*
Bactericidal for Gram-⊕ cocci/rods, Gram-⊖ cocci, spirochetes; Extended-spectrum
penicillin: *H.* influenzae, *H.* pylori, *E.* coli, *L*isteria monocytogenes, *P*roteus
mirabilis, *S*almonella, *S*higella, enterococci. *HHELPSS*
*Toxicity:*
Hypersensitivity reactions (type II), ampicillin rash (often with EBV infection- reaction-not
an allergy), pseudomembranous colitis
*MOR:*
β-lactamase activity
Ticarcillin
Piperacillin Ans- Ureidopenicillins: "Antipseudomonals"
*MOA:*
Same as penicillin. Extended spectrum.
*Clinical use:*
*Pseudomonas spp.* and Gram-⊖ rods
Hospital-acquired pneumonias (Klebsiella, H. influenzae, Enterobacter)
Susceptible to penicillinase; use with β-lactamase inhibitors.
*Toxicity:*
Hypersensitivity reactions (type II)
Clavulanic Acid
Sulbactam
Tazobactam Ans- *MOA:*
β-lactamase inhibitors
*Clinical use:*
Often added to penicillin antibiotics (aminopenicillins, antipseudomonals) to protect the
antibiotic from destruction by β-lactamase (penicillinase).
"*CAST*" - *C*lavulanic *A*cid, *S*ulbactam, *T*azobactam
Cefadroxil
Cephalexin
Cephradine (PO)
,Cefazolin (IV)
Cefazolin
Cephalexin Ans- *1st Generation Cephalosporins*
*MOA:*
Same as that of penicillins
*Clinical use:*
Gram-⊕ cocci: streptococci, methicillin-susceptible staphylococci
Community-acquired strains of enteric Gram-⊖ rods, *P*roteus spp., *E. c*oli,
*K*lebsiella spp. (*PEcK*)
Cefazolin: used prior to surgery to prevent S. aureus wound infections.
*Toxicity:*
Hypersensitivity reactions, autoimmune hemolytic anemia, disulfiram-like reaction,
vitamin K deficiency. Exhibit cross-reactivity with penicillins. Potentiate the
nephrotoxicity of aminoglycosides.
*MOR:*
Structural change in penicillin-binding proteins (transpeptidases).
All cephalosporins are typically inactive against *L*isteria monocytogenes, *A*typical
pneumonias (Chlamydia, Mycoplamsa), *M*RSA, and *E*nterococci. (*LAME*)
Cefaclor (PO)
Cefuroxime (PO)
Cefoxitin (IV) Ans- *2nd Generation Cephalosporins*
*MOA:*
Same as that of penicillins
*Clinical use:*
Less activity than 1st generation against Gram-⊕ cocci, though enough be useful; more
activity against enteric Gram-⊖ rods
*Cefuroxime & cefaclor:* Haemophilus influenzae and Neisseria meningitides
*Cefoxitin:* very active against enteric anaerobes (Bacteroides & Prevotella spps.)
*HEN PEcKS* *H*aemophilus influenzae, *E*nterobacter aerogenes, *N*eisseria spp.,
*P*roteus mirabilis, *E. c*oli, *K*lebsiella, *S*erratia marcescens.
*Toxicity:*
Hypersensitivity reactions, autoimmune hemolytic anemia, disulfiram-like reaction,
vitamin K deficiency. Exhibit cross-reactivity with penicillins. Potentiate the
nephrotoxicity of aminoglycosides.
*MOR:*
Structural change in penicillin-binding proteins (transpeptidases).
, All cephalosporins are typically inactive against *L*isteria monocytogenes, *A*typical
pneumonias (Chlamydia, Mycoplamsa), *M*RSA, and *E*nterococci. (*LAME*)
*Ceftriaxone*
Cefotaxime
Ceftazidime
Cefixime
Cefpodoxime
Loracarbef (PO) Ans- *3rd Generation Cephalosporins*
*MOA:*
Same as that of penicillins
*Clinical use:*
Serious Gram-⊖ infections resistant to other β-lactams.
More activity against nosocomial Gram-⊖ bacilli, like Enterobacter spp., Citrobacter
spp., and Serratia marcescens
*Ceftriaxone:* Neisseria spp., disseminated Lyme disease, anthrax, H. influenzae
meningitis, S. typhi
*Ceftazidime:* some activity against Pseudomonas spp. but less against Gram-⊕ cocci;
the opposite is true for ceftriaxone, cefotaxime, and the oral 3rd generation drugs
*Toxicity:*
Hypersensitivity reactions, autoimmune hemolytic anemia, disulfiram-like reaction,
vitamin K deficiency. Exhibit cross-reactivity with penicillins. Potentiate the
nephrotoxicity of aminoglycosides.
*MOR:*
Structural change in penicillin-binding proteins (transpeptidases).
All cephalosporins are typically inactive against *L*isteria monocytogenes, *A*typical
pneumonias (Chlamydia, Mycoplamsa), *M*RSA, and *E*nterococci. (*LAME*)
Cefepime Ans- *4th Generation Cephalosporins*
*MOA:*
Same as that of penicillins.
Binds PBP 2z, which is produced by MRSA strains
*Clinical use:*
Combines the features of 3rd generation cephalosporins broad activity against
streptococci, methicillin-susceptible staphylococci, and Gram-⊖ bacilli including
nosocomial strains and with ↑ activity against *Pseudomonas*
*Toxicity:*
Hypersensitivity reactions, autoimmune hemolytic anemia, disulfiram-like reaction,
vitamin K deficiency. Exhibit cross-reactivity with penicillins. Potentiate the
nephrotoxicity of aminoglycosides.
(Complete)
Penicillin G (IV and IM)
Penicillin M (oral) Ans- *MOA:*
*β-lactam*: a structural analog of D-ala-D-ala (a normal component of cell walls) which
binds and inactivates bacterial transpeptidases (penicillin-binding protein, PBPs) to
block peptidoglycan cross linking
*Clinical use:*
Bactericidal for Gram-⊕ cocci/rods, Gram-⊖ cocci (Neisseria), and spirochetes
Mostly used for Gram-⊕ organisms (S. pneumoniae, S. pyogenes, Actinomyces). Also
used for Gram-⊖ cocci (mainly N. meningitidis) and spirochetes (namely T. pallidum).
Bactericidal for Gram-⊕ cocci, Gram-⊕ rods, Gram-⊖ cocci, and spirochetes.
Penicillinase sensitive.
*Toxicity:*
Hypersensitivity reactions (type II), hemolytic anemia
*MOR:*
Penicilinase (a type of β-lactamase) in bacteria cleaves
Oxacillin
Nafcillin
Dicloxacillin Ans- Penicillinase-resistant penicillins
*MOA:*
Same as penicillin.
*Narrow spectrum*; penicillinase resistant because bulky R group blocks access of β-
lactamase to β-lactam ring.
*Clinical use:*
Bactericidal, narrow spectrum: *S. aureus* (except MRSA; resistant due to altered
penicillin-binding protein target site).
*Toxicity:*
Hypersensitivity reactions (type II), interstitial nephritis
"Use *naf* (*naf*cillin) for staph." Nafcillin has penetration to CNS
Aminopenicillins:
,Ampicillin
Amoxicillin Ans- Penicillinase-sensitive penicillins
*MOA:*
Same as penicillin.
Wider spectrum with better activity against Gram-⊖ bugs; penicillinase sensitive.
Administer with clavulanic acid to protect against destruction by β-lactamase.
*Clinical use:*
Bactericidal for Gram-⊕ cocci/rods, Gram-⊖ cocci, spirochetes; Extended-spectrum
penicillin: *H.* influenzae, *H.* pylori, *E.* coli, *L*isteria monocytogenes, *P*roteus
mirabilis, *S*almonella, *S*higella, enterococci. *HHELPSS*
*Toxicity:*
Hypersensitivity reactions (type II), ampicillin rash (often with EBV infection- reaction-not
an allergy), pseudomembranous colitis
*MOR:*
β-lactamase activity
Ticarcillin
Piperacillin Ans- Ureidopenicillins: "Antipseudomonals"
*MOA:*
Same as penicillin. Extended spectrum.
*Clinical use:*
*Pseudomonas spp.* and Gram-⊖ rods
Hospital-acquired pneumonias (Klebsiella, H. influenzae, Enterobacter)
Susceptible to penicillinase; use with β-lactamase inhibitors.
*Toxicity:*
Hypersensitivity reactions (type II)
Clavulanic Acid
Sulbactam
Tazobactam Ans- *MOA:*
β-lactamase inhibitors
*Clinical use:*
Often added to penicillin antibiotics (aminopenicillins, antipseudomonals) to protect the
antibiotic from destruction by β-lactamase (penicillinase).
"*CAST*" - *C*lavulanic *A*cid, *S*ulbactam, *T*azobactam
Cefadroxil
Cephalexin
Cephradine (PO)
,Cefazolin (IV)
Cefazolin
Cephalexin Ans- *1st Generation Cephalosporins*
*MOA:*
Same as that of penicillins
*Clinical use:*
Gram-⊕ cocci: streptococci, methicillin-susceptible staphylococci
Community-acquired strains of enteric Gram-⊖ rods, *P*roteus spp., *E. c*oli,
*K*lebsiella spp. (*PEcK*)
Cefazolin: used prior to surgery to prevent S. aureus wound infections.
*Toxicity:*
Hypersensitivity reactions, autoimmune hemolytic anemia, disulfiram-like reaction,
vitamin K deficiency. Exhibit cross-reactivity with penicillins. Potentiate the
nephrotoxicity of aminoglycosides.
*MOR:*
Structural change in penicillin-binding proteins (transpeptidases).
All cephalosporins are typically inactive against *L*isteria monocytogenes, *A*typical
pneumonias (Chlamydia, Mycoplamsa), *M*RSA, and *E*nterococci. (*LAME*)
Cefaclor (PO)
Cefuroxime (PO)
Cefoxitin (IV) Ans- *2nd Generation Cephalosporins*
*MOA:*
Same as that of penicillins
*Clinical use:*
Less activity than 1st generation against Gram-⊕ cocci, though enough be useful; more
activity against enteric Gram-⊖ rods
*Cefuroxime & cefaclor:* Haemophilus influenzae and Neisseria meningitides
*Cefoxitin:* very active against enteric anaerobes (Bacteroides & Prevotella spps.)
*HEN PEcKS* *H*aemophilus influenzae, *E*nterobacter aerogenes, *N*eisseria spp.,
*P*roteus mirabilis, *E. c*oli, *K*lebsiella, *S*erratia marcescens.
*Toxicity:*
Hypersensitivity reactions, autoimmune hemolytic anemia, disulfiram-like reaction,
vitamin K deficiency. Exhibit cross-reactivity with penicillins. Potentiate the
nephrotoxicity of aminoglycosides.
*MOR:*
Structural change in penicillin-binding proteins (transpeptidases).
, All cephalosporins are typically inactive against *L*isteria monocytogenes, *A*typical
pneumonias (Chlamydia, Mycoplamsa), *M*RSA, and *E*nterococci. (*LAME*)
*Ceftriaxone*
Cefotaxime
Ceftazidime
Cefixime
Cefpodoxime
Loracarbef (PO) Ans- *3rd Generation Cephalosporins*
*MOA:*
Same as that of penicillins
*Clinical use:*
Serious Gram-⊖ infections resistant to other β-lactams.
More activity against nosocomial Gram-⊖ bacilli, like Enterobacter spp., Citrobacter
spp., and Serratia marcescens
*Ceftriaxone:* Neisseria spp., disseminated Lyme disease, anthrax, H. influenzae
meningitis, S. typhi
*Ceftazidime:* some activity against Pseudomonas spp. but less against Gram-⊕ cocci;
the opposite is true for ceftriaxone, cefotaxime, and the oral 3rd generation drugs
*Toxicity:*
Hypersensitivity reactions, autoimmune hemolytic anemia, disulfiram-like reaction,
vitamin K deficiency. Exhibit cross-reactivity with penicillins. Potentiate the
nephrotoxicity of aminoglycosides.
*MOR:*
Structural change in penicillin-binding proteins (transpeptidases).
All cephalosporins are typically inactive against *L*isteria monocytogenes, *A*typical
pneumonias (Chlamydia, Mycoplamsa), *M*RSA, and *E*nterococci. (*LAME*)
Cefepime Ans- *4th Generation Cephalosporins*
*MOA:*
Same as that of penicillins.
Binds PBP 2z, which is produced by MRSA strains
*Clinical use:*
Combines the features of 3rd generation cephalosporins broad activity against
streptococci, methicillin-susceptible staphylococci, and Gram-⊖ bacilli including
nosocomial strains and with ↑ activity against *Pseudomonas*
*Toxicity:*
Hypersensitivity reactions, autoimmune hemolytic anemia, disulfiram-like reaction,
vitamin K deficiency. Exhibit cross-reactivity with penicillins. Potentiate the
nephrotoxicity of aminoglycosides.
