Antibacterial Agents II - Cell Wall Synthesis Inhibitors

Question 1

Penicillin: mechanism of action

Answer 1

competitive inhibitor of the transpeptidase enzyme; inhibits cell wall synthesis

Question 2

Penicillin: absorption

Answer 2

• optimal absorption from an empty stomach
• Penicillin G: IV and IM
• PO Penicillin V and Amoxicillin
• Piperacillin IV only

Question 3

Penicillin: distribution

Answer 3

• penetrate into tissues poorly (highest concentration in the liver, kidney, skin)
• can enter inflamed tissues or membranes more readily than normal

Question 4

Penicillin: metabolism/excretion

Answer 4

• tubular secretion (kidney)
• metabolism often increases to complensate in cases of renal failure
• excreted in breast milk

Question 5

Penicillin: spectrum of activity/major uses

G+cocci

Answer 5

• Strep = PenG, PenV, Amoxicillin
• Enterococci = PenG, Ampicillin
• Staph = Oxacillin [MSSA] [NO PENICILLINS FOR MRSA]

Question 6

Penicillin: spectrum of activity/major uses

G-cocci

Answer 6

-N. gonorrhea = PenG

Question 7

Penicillin: spectrum of activity/major uses

G+bacilli

Answer 7

• B. anthracis = PenG

- C. diptheria = PenG

Question 8

Penicillin: spectrum of activity/major uses

G-bacilli

Answer 8

• E. coli

- P. aeruginosa= (Amoxicillin-Clavulanate, Piperacillin - Tazobactam

Question 9

Penicillin: spectrum of activity/major uses

anaerobes

Answer 9

• C. perfringens (G+r) = Piperacillin - Tazobactam

- B. fragilis (G-r) = Piperacillin - Tazobactam

Question 10

Penicillin: Adverse effects/DDIs

Answer 10

Virtually nontoxic
A. hypersensitivity reactions due to presence of preformed IgE (Anaphylactic shock, urticaria, rash) - RARE!
B. diarrhea (common!)

Question 11

Vancomycin: mechanism of action

Answer 11

Tricyclic glycopeptide acts by inhibiting cell wall synthesis (blocks glycopeptide polymerization via binding tightly to D-alanyl-D-alanine portion of cell wall precursor, Stage 2 of cell wall synthesis).

Question 12

Vancomycin: Pharmacokinetics

Answer 12

• Poor oral absorption, administered IV, except for GI tract indications (e.g., Clostridium, but metronidazole is now preferred agent due to resistance concerns and expense of vancomycin).
• Excretion mainly through kidneys, in renal failure half-life extended to 6-10 days

Question 13

Vancomycin: Spectum of activity/Major clinical uses

Answer 13

1. covers all g+, including
   - –MRSA
   - –Enterococcus
   - –strep
2. c. dif (used orally)
3. g+ organisms for patients who are allergic to penicillin and cephalosporin

Question 14

Vancomycin: Side effects

Answer 14

“Red man syndrome”

Chills-fever-skin rash (infusion-related - just infuse slower), ototoxicity most severe (pretreat with acetaminophen and diphenhydramine).