Beta-Lactams/Cephalosporins

Question 1

Beta-Lactam Antibiotics

Answer 1

• Moa: Inhibit bacterial cell wall synthesis by binding Penicillin-binding proteins which are necessary for peptidoglycan synthesis
• Only effective against actively multiplying bacteria

Question 2

Bacterial methods of resistance

Answer 2

• Beta-lactamase
• Reduced # of PBP’s
• Decreased affinity for drug
• Diminished cell wall permeability

Resistance is always increasing

Question 3

Natural PCN’s

Answer 3

• Penicillin G (IM)
• Penicillin V (Oral)
• Susceptibility: Gram + bacteria
  
  • Strep. pneumoniae, Staphylococcus, bacillus anthrax, Gram + anaerobes
• FIRST LINE: Group A beta-hemolytic strep
  
  • Strep throat, Treponema pallidum (syphilis)
• Beta-lactamase susceptable

Question 4

1st line treatment for Group A beta-hemolytic streptococcus

Answer 4

Penicillin G (IM)
Penicillin V (Oral)

Question 5

PCN’s w/beta-lactamase inhibitors

Answer 5

• Amoxicillin/Clavulanic acid (Augmentin)
• Ampicillin/Sulbactam (Unasyn)
• Susceptible: G+, some G-
• FIRST LINE: Sinusitis
• More expensive
• More GI side effects

Question 6

Antistaphylococcal PCN’s

Answer 6

• Dicloxacillin
• Methicillin
• Nafcillin
• Susceptible: Staphylococci
• Indications: Skin/soft tissue infections
• Resistant to beta-lactamase
• Methicillin is not for treatment, only diagnosis of MRSA

Question 7

Antipseudomonal PCN’s

Answer 7

• Piperacillin
• Ticarcillin
• Susceptible: G+, increased G-, including psuedomonas
• Only for severe infections
• Indications: Nosocomial pneumonia, peritonitis, PID, severe skin infections
• Only available w/beta-lactamase inhibitor
  
  • Piperacillin/Tazobactam (Zosyn)
• Think “wet” and “water” for pseudomonas

Question 8

Cephalosporins

Answer 8

• MOA: Inhibit bacterial cell wall synthesis (like PCN’s)
• More More resistant to beta-lactamase
• 2nd line treatment
• 4 generations
  
  • Higher gen = better for G-
  • Lower gen = better for G+

Question 9

1st Generation Cephalosporins

Answer 9

• PROTOTYPE: Cephalexin (Keflex)
• Indications: Minor skin infections, impetigo, pharyngitis/OM
• G- (E. coli), UTI especially in pregnancy
• Very affordable
  Oral 4x daily (adherence issue)
• Cefazolin (Ancef/Kefzol)
  
  • IV/IM only, surgical prophylaxis

Question 10

2nd Generation Cephalosporins

Answer 10

• Cefuroxime
• Cefoxitin
• Cefotetan
• Susceptible: Variable
• Varying routes of entry
• Indications:
  
  • Cefoxitin/Cefotetam: better G- coverage, surgical prophylaxis for “dirty” procedures
  • Cefuosime: 2nd line for pharyingitis, sinusitis, OM

Question 11

3rd Generation Cephalosporins

Answer 11

• Ceftriaxone (Rocephin)
• Indications:
  
  • 1ST LINE n. gonorrhoeae
  • surgical prophylaxis
  • meningitis
  • PID
• IM/IV

Question 12

4th Generation Cephalosporins

Answer 12

• Cefepime (Maxipime)
• Susceptible: G+, G-, pseudomonas
• Indications: Severe infections

Question 13

Beta-Lactam Side effects

Answer 13

• GI (N/V/D) more likely w/augmentin

- Vaginal candidiasis

Question 14

Beta-Lactam adverse events

Answer 14

• Hypersensitivity: rash, bronchospasm
• C. diff colitis
• Nephritis
• Heme abnormalities
• Special considerations: reduced effectiveness of oral contraceptives