Dr. Roane Macrolides, Clindamycin, Linezolid, etc

Question 1

Macrolide MOA

Answer 1

-Macrolides and Clindamycin probably share the same MOA
-binding to the 50S subunit and inhibiting ribosome translocation

Question 2

Macrolides

Answer 2

Azithromycin
Erythromycin
Clarithromycin

Question 3

Which drug class shares the same MOA with Macrolides?

Answer 3

Clindamycin

Question 4

Spectrum of Activity

Answer 4

-Broad spectrum
-Gram (+): Staph, Strep
-Gram (-)
-Syphilis
-Chlamydia
-Mycoplasma Pneumonia

Question 5

Which pneumonia is referred to as “walking” pneumonia?

Answer 5

Mycoplasma pneumonia - not so sick so pt can walk
-considered atypical -> Erythromycin and tetracyclines are effective

Question 6

Which of the Macrolides has the longest half-life?

Answer 6

Azithromycin 40 hrs
Zpak PO

Question 7

What causes high levels of drugs when a patient takes Chloramphenicol?

Answer 7

Erythromycin and Clarithromycin inhibit CYP450
CYP450 cant metabolize other drugs -> increase in concentration

Question 8

What is a prokinetic effect?

Answer 8

Stimulation of gastric motility (Erythromycin)

Question 9

Adverse effects of Macrolides

Answer 9

-GI disturbance, cramping -> used in Erythromycin (prokinetic effect)
-Cholestatic Jaundice
-Ototoxicity

Question 10

What is a QTc?

Answer 10

calculated average interval between Q-wave and T-wave

Question 11

Which Microlide is associated with prolongation of the QTc interval?

Answer 11

Telithromycin (Ketek)

Question 12

Consequence of QT prolongation

Answer 12

-Increased risk of heart attack
-Torsades de pointes (twisting of points)

Question 13

Which Macrolide treats Pseudomembranous colitis (superinfection) of the colon due to overgrowth of C. diff?

Answer 13

Fidaxomicin (Dificid)

Question 14

Why is the Activity of Fidaxomicin limited to the colon?

Answer 14

Due to its poor oral availability

Question 15

What is the resistance mechanism of bacteria against Macrolides?

Answer 15

Erythromycin ribosome methylation ERM genes: ERMa ERMb responsible for:
-methylation of the ribosomal binding site -> prevention of binding

-Efflux pump

Question 16

What is the purpose of the D-test?

Answer 16

-Do Macrolides induce resistance to Clindamycin?

-it depends on if the ERM gene coding for MLS is ON -> it methylates ribosomal RNA preventing binding of macrolides, clindamycin, and streptogramins

-It affects the activity of Clindamycin bc they share the same MOA

Question 17

What are the semisynthetic drugs derived from Streptogramins?

Answer 17

Quinupristin/dalfopristin (Synercid)

Question 18

What is the MOA of Quinupristin/dalfopristin?

Answer 18

-Binding to separate sites of the 50S ribosome -> synergistic effect to inhibit protein synthesis

-long-lasting post-antibiotic effect (PAE)

Question 19

Which CYP is affected by Quinupristin/dalfopristin?

Answer 19

CYP 3A4

Question 20

Oxazolidinones

Answer 20

-Linezolid (Zyvox)
-Tedizolid (Sivextro

-chemical synthesized

Question 21

Linezolid MOA

Answer 21

Inhibits the formation of 70S
->Blocks assembly of the initiation complex

Question 22

Linezolid shares the MOA with which drug?

Answer 22

-Chloramphenicol

-blocking peptide bond formation
-Resistance due to altering the binding site

Question 23

What is an important indication of Linezolid?

Answer 23

-ABSSSI (Acute Bacterial Skin and skin structure infection)
-alternative to Vancomycin

Question 24

Why does Linezolid have such a high number of drugs it interacts with?

Answer 24

Because it blocks MOA (monoamine oxidase)
MOA is responsible for metabolizing a variety of drugs into their inactive form