Dr. Cluck Anti-Infective Penems and Aztreonam

Question 1

What are the Carbapenems?

Answer 1

Imipenem-Cilastin (Cilastatin prevents breakdown of Imipenem): has the best gram-positive coverage
Meropenem: CNS infections
Ertapenem
-> IV, IM

Question 2

Spectrum of Activity - Carbapenems

Answer 2

Broad:
-Gram-positive: PRSP (PNC-res-strep pneumo.), MSSA, VSE
-Gram-negative: most gram-negatives (Acinetobacter, Pseudomonas)

Question 3

Where do Carbapenems lack activity against microbials?

Answer 3

-Ertapenem (Monkey-cillin): Pseudomonas, Acinetobacter, Enterococcus spp (KNOW THIS!)
A-P-E

-All: Stenotrophomonas, Legionella, MRSA, VRE

Question 4

How does Stenotrophomonas (gram-negative) neutralize Carbapenems?

Answer 4

They produce Metallo-ß-lactamase which hydrolyzes Carbapenems

Question 5

How can Legionella be treated?
Carbapenem-resistant

Answer 5

Fluoroquinolone, macrolides

Question 6

Which drug to use for MRSA?

Answer 6

The only ß-lactam that covers MRSA: Ceftaroline

What about VNC?

Question 7

Which drugs cover Vancomyin-resistant microbes?

Answer 7

Linezolid, Daptomycin

Question 8

What drug formulation is used for Carbapenems?

Answer 8

IV only

Question 9

Pharmacokinetics of Carbapenems

Answer 9

-Absorption: Well absorbed
-Distribution: Well throughout the body + CSF
-Metabolism/Excretion: predominantly in the urine/no metabolism

Question 10

Contraindications of Carbapenems

Answer 10

Hypersensitivity (not common)

Question 11

Adverse effects of Carbapenems

Answer 11

-Seizures (almost exclusive to imipenem) - have to renal adjust !!
-C. diff infection - due to broad-spectrum activity

Question 12

Drug Interactions of Carbapenems

Answer 12

-Probenecid - results in increased level of Carbapenems

-Valproic acid (seizures and mood stabilization): using Carbapenems simultaneously results in low levels of Valproic acid (50-80% after 24h of giving Carbapenem) - This cannot be overcome by simply increasing Valproic acid bc Carbapenem is so effective at lowering VPA - EXAM

Question 13

What is the only Monobactam?

Answer 13

Azactam (aztreonam)
-ONLY cover anaerobic gram-negatives including Pseudomonas (but other drugs are better for Pseudomonas)

-used in PNC-allergic patients - often patients are not actually allergic and even if they can use Cephalosporin or Carbapenem

-eliminated renally
-stable to Metallo-ß-lactamases (hydrolyzes carbapenem)
EXPENSIVE

Question 14

Which Mechanisms of Resistance do microbes use against Carbapenems?

Answer 14

-ß-lactamases
-PBP modification (binding site of drug)
-can not penetrate the outer membrane through porins anymore (porins down-regulated)
-Clearance of the drug via efflux pumps

Question 15

What would be the first line to treat an infection empirically?

Answer 15

ß-lactams - unless a specific case is stated

Question 16

Which drug class has low Cross-reactivity?

Answer 16

Carbapenems

Question 17

What is the danger of overusing Carbapenems?

Answer 17

Resistance -> KPC

Question 18

What is an alternative drug for patients with anaphylactic-type reactions to penicillin?

Answer 18

Aztreonam (Monobactam) or use other drug class

Question 19

Which Carbapenem is appropriate for a CNS infection

Answer 19

Meropenem

Question 20

Which organism is not covered by Ertapenem

Answer 20

A-P-E