Carbapenems and Monobactams

Question 1

What are the carbapenems available?

Answer 1

Imipenem
Doripenem
Meropenem
Ertapenem

Question 2

Describe the structure of a carbapenem

Answer 2

Beta lactam ring attached to a 5 membered ring (like the penicillins)

Question 3

Mechanism of Action of Carbapenems

Answer 3

Inhibit cell wall synthesis by binding PBPs. Carbapenems are selective for PBP2.

Question 4

Cabapenems exhibit ____-dependent bacteri____ activity.

Answer 4

Time dependent bactericidal activity

Question 5

Mechanisms of Resistance to Carbapenems

Answer 5

Beta-lactamase production
Decreased permeability
Alterations in PBPs

Question 6

Carbapenems generally have a very _____ spectrum of activity

Answer 6

BROAD

There is activity against Gram positive and negative aerobes and anaerobes

Question 7

Which carbapenems are best for Gram Positive infections? What organisms would be most susceptible to those?

Answer 7

Imipenem and Doripenem

MSSA
PSSP
Group and viridians strep
Enterococcus (static activity)

Question 8

Which carbapenems are best for Gram Negative infections?

Answer 8

Doripenem and Meropenem

Question 9

Which carbapenem should NEVER be used for a Pseudomonas infection?

Answer 9

Ertapenem

Question 10

What bacteria are carbapenems NOT active against?

Answer 10

MRSA
PRSP
Coagulase negative staph
VRE
C diff
Atypical bacteria
Stenotrophomonas

Question 11

Carbapenems
Distribution

Which penetrates CSF best?

Answer 11

Wide distribution.

Meropenem penetrates CSF best.

Question 12

Carbapenems

Elimination

Answer 12

Mostly eliminated by the kidney

Question 13

Describe the elimination of imipenem. What should be coadministered with imipenem?

Answer 13

Imipenem is hydrolyzed to a nephrotoxic metabolite by a DHP enzyme. This causes Imipenem to be cleared too quickly. Use a DHP inhibitor (cilastin) to prevent this and make imipenem last longer

Question 14

Carbapenems

Adverse Effects

Answer 14

Hypersensitivity in 3% of patients (15% cross reactivity with penicillins)

CNS- HA, confusion, seizures

Question 15

Carbapenems

Clinical Uses

Answer 15

Empiric therapy for hospital acquired infections
Polymicrobial Infections
Infections due to Beta-lactamase producing enzymes

Remember, if Pseudomonas is known or suspected, do NOT use ertapenem

Question 16

What is the only monobactam currently available?

Answer 16

Aztreonam

Question 17

Basic structure of Monobactams

Answer 17

Monocyclic Beta-lactam ring

Question 18

Monobactams exhibit ____-dependent bacteri____ activity.

Answer 18

Time dependent bactericidal activity

Question 19

Monobactams

Mechanism of Action

Answer 19

Bind PBPs to inhibit cell wall synthesis. Preferentially binds PBP3.

Question 20

Monobactams Spectrum of Activity

Answer 20

Highly selective for Gram Negative Aerobes

No activity for Gram Positive aerobes or anaerobes.

Question 21

Monobactam Distribution

Does it penetrate the CSF?

Answer 21

Only available IV

Only penetrates the CSF in the presence of inflammed meninges

Question 22

Monobactam Elimination

Answer 22

Primarily renally eliminated.

Adjust dosing in renal dysfunction.

Question 23

Aztreonam Adverse Effects

Answer 23

GI - nausea, diarrhea

Question 24

Aztreonam Hypersentivity

Answer 24

NO Cross reactivity with penicillins, so aztreonam is safe to use in penicillin-allergic patients