Macrolides

Question 1

How do the Macrolides work?

Answer 1

Bacteriostatic
Inhibition of protein synthesis
-50S ribosomal subunits of sensitive bacteria

Question 2

What are the Macrolides?

Answer 2

• Erythromycin
• Clarithromycin
• Azithromycin

Question 3

What are the characteristics of Erythromycin?

Answer 3

• Inexpensive
• Four times a day dosing (short half-life)
• Excreted Biliary –> no renal adjustment

Question 4

What are the characteristics of Clarithromycin?

Answer 4

• Compared to erythromycin- more acid stable, better absorption, prolonged half life, steady state after 5 doses
• Twice a day dosing
• Excreted Biliary/Renal

Question 5

What are the characteristics of Azithromycin?

Answer 5

• Compared to erythromycin- more acid stable, rapid extensive uptake from circulation to intracellular compartment
• Peak serum concentrations lower than other two but larger volume of distribution
• Once a day dosing
• Excreted Biliary –> no renal adjustment

Question 6

What does Erythromycin kill?

Answer 6

Gram-positive cocci and some gram-negative

Question 7

What does Clarithromycin kill?

Answer 7

Better gram-positive activity compared to erythromycin and azithromycin; better gram-negative coverage than erythromycin

Question 8

What does Azithromycin kill?

Answer 8

Gram-positive coverage similar to erythromycin; increased gram-negative coverage that clarithromycin; more effective than clarithromycin for H. influenzae

Question 9

What is Erythromycin used for?

Answer 9

Mild to moderate upper respiratory, lower respiratory tract, respiratory tract infection due to Mycoplasma pneumoniae, mild to moderate skin and skin structure, diphtheria, pertussis

Question 10

What is Clarithromycin used for?

Answer 10

Pharyngitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, community acquired pneumonia, uncomplicated skin and skin structure, disseminated mycobacterial infections, acute otitis media

Question 11

What is Azithromycin used for?

Answer 11

Acute exacerbation of chronic obstructive pulmonary disease, community acquired pneumonia, streptococcal pharyngitis/tonsillitis, uncomplicated skin and skin structure, non-gonoccocal urethritis and cervicitis, disseminated Mycobacterium avium complex disease, Legionnaires’ disease

Question 12

What are possible side effects of the Macrolides?

Answer 12

• Adverse reaction profile, differs with each agent
  
  • Erythromycin- gastrointestinal, QT prolongation, drug interactions
  • Clarithromycin- gastrointestinal, dysgeusia, headache, drug interactions
  • Azithromycin- gastrointestinal
• Cardiac risk with azithromycin
  
  • Rare occurrence
    - FDA warning should scare everyone? –> No, is ok for healthy, young people. Not good for at risk patients with heart problems.

Question 13

What are the types of resistance with the Macrolides?

Answer 13

Drug efflux
Decreased drug binding at the ribosome
Hydrolysis by esterases
Mutation of the 50S ribosomal protein

Question 14

Prescription for Erythromycin (base)?

Answer 14

500 mg

One tablet every six (6) hours

Question 15

Prescription for Azithromycin?

Answer 15

500 mg
One tablet once a day daily

Community acquired pneumonia –> 7-14 days