Penicillins

Question 1

Describe the MOA of penicillins.

Answer 1

interfere w/ cell wall synthesis by binding to and inhibiting PBPs located in bacterial cell membranes (inhibition of PBPs leads to inhibition of final transpeptidation step of peptidoglycan synthesis)

Question 2

Describe the expression of PBPs.

Answer 2

• number, type, and location vary b/t bacteria

- only expressed during cell division

Question 3

Which bacteria produce β-lactamase enzymes?

Answer 3

• Gram (+): penicillin-resistant S. aureus
• Gram (-): H. influenzae, Moraxella catarrhalis, N. gonorrhoea, E. coli, K. pneumoniae, Enterobacter spp. (almost all gram negatives)
• Gram (-) anaerobes: B. fragilis

Question 4

About ____% of S. aureus are penicillin-resistant and ____% are methicillin-resistant (MRSA).

Answer 4

99; 50

Question 5

Are penicillins time-dependent or concentration-dependent?

Answer 5

They exhibit time-dependent bacterial killing. (time about MIC correlates w/ efficacy)

Question 6

With the penicillins, is there a post-antibiotic effect (PAE) for gram (-) bacteria?

Answer 6

No!

Question 7

Penicillins can be used synergistically with ________ to fight against _________.

Answer 7

aminoglycosides; Enterococcus, Staphylococcus, Viridans strep, and gram negatives

Question 8

True or false: oral penicillins may be used interchangeably for their IV equivalents.

Answer 8

False: Oral penicillins are variably absorbed, and concentrations from oral formulations are lower than from IV formulations.

Question 9

Penicillins are widely distributed into tissues and fluids, except for:

Answer 9

the eye, prostate, and uninflamed CSF

Question 10

For which penicillins do we worry about sodium load?

Answer 10

Penicillin G, Ticarcillin, and Piperacillin

Question 11

Which drug blocks renal tubular secretion of penicillins? What is the implication?

Answer 11

Probenecid, which may be used in conjunction with a penicillin to boost serum levels during serious infections.

Question 12

Do penicillins have short or long elimination half lives?

Answer 12

Short (<2hrs), except for procaine penicillin G and benzathine penicillin G.

Question 13

Which penicillins are NOT eliminated by the kidney?

Answer 13

The PRPs, which are eliminated by the liver and do NOT require dose adjustment in renal insufficiency.

Question 14

Which penicillin is uniquely used for bite wounds and why?

Answer 14

Augmentin, because it has very good gram (-) coverage

Question 15

True or false: cross-reactivity exists among all penicillins but NOT other beta-lactams.

Answer 15

False: cross-reactivity exists among ALL penicillins AND some beta-lactams

Question 16

Which penicillin poses the highest risk for renal failure?

Answer 16

nafcillin