Protein Synthesis Inhibitors

Question 1

What 5 drug classes are Protein Synthesis Inhibitors and what is their overall mechanism of action?

Answer 1

1. Macrolides - 50s inhibition
2. Tetracyclines - 30s inhibition
3. Aminoglycosides - 30s inhibition
4. Clindamycin - 50s inhibition
5. Chloramphenicol - 50s inhibition

MOA: bind to 50s or 30s ribosomal subunit = BACTERIOSTATIC

Question 2

What are the 3 common macrolides and what coverage do they have?

Answer 2

Azithromycin, Erythromycin, Clarithromycin - 50s inhibitor

Coverage: ATYPICAL organisms (legionella, mycoplasma, chlamydia), some Gram + cocci, some Gram -

Question 3

What is the drug of choice for Atypical (Legionella, Mycoplasma, Chlamydia) bacterial infections?

Answer 3

Azithromycin

Question 4

What is the main use of the macrolide erythromycin?

Answer 4

GI motility agent

Question 5

What are the 3 main side effects of Macrolides?

Answer 5

1. QT prolongation
2. prominent GI effects
3. rash

Question 6

What are the 3 common Tetracyclines and what 7 unusual organisms do they cover?

Answer 6

Doxycycline, Tetracycline, Minocycline - 30s inhibition

Coverage: Staph/MRSA, some Gram -, Atypicals

Special coverage: Rickettsia, Lyme Dz, Tularemia, Vibrio, Brucella, Q Fever, Anthrax

Question 7

What is the most commonly used Tetracycline and why?

Answer 7

Doxycycline - BID dosing, little food interaction, and excellent bioavailability

Question 8

What is the Abx of choice for early Lyme Dz and Lyme Dz prophylaxis following tick bite?

Answer 8

Doxycycline

Question 9

What are the 3 main indications for Tetracycline Abx use?

Answer 9

1. skin/soft tissue infections (MRSA)
2. respiratory infections
3. unusual organisms (animal stuff)

Question 10

What are 5 common side effects of Tetracycline use?

Answer 10

1. teratogenic
2. photosensitivity
3. teeth discoloration
4. bone growth inhibition in children
5. steatosis/hepatotoxicity

Question 11

What are 3 other conditions that Doxycycline can be used to treat?

Answer 11

1. acne
2. rosacea
3. malaria prophylaxis

Question 12

What coverage does Clindamycin have and what empiric treatment is it commonly used for?

Answer 12

50s inhibitor with excellent anaerobe and Gram + (50% MRSA) coverage, but not Enterococcus

Empiric: Staph/Strep cellulitis

Question 13

Why is Clindamycin used for TSS and NEC?

Answer 13

Has significant antitoxin effect against Group A Strep

Question 14

What is Clindamycin not useful for brain abscesses or severe intraabdominal infections?

Answer 14

• does NOT penetrate CSF
• increasing resistance in Bacteroides organisms

Question 15

What antibiotic has the highest rate of C. diff infection following its use?

Answer 15

Clindamycin

Question 16

What are the 4 common Aminoglycosides and what coverage do they provide?

Answer 16

Gentamicin, Tobramycin, Amikacin, Streptomycin - 30s inhibition IV ONLY

Coverage: Aerobic Gram -, Pseudomonas but NO Gram + or anaerobe activity

Question 17

What are 3 serious side effects of Aminoglycoside use?

Answer 17

1. ATN (reversible)
2. Nephrotoxicity (reversible)
3. Oto/vestibular toxicity (irreversible)

Question 18

How does aminoglycoside killing work?

Answer 18

CONCENTRATION-dependent

• more efficacy with higher peak concentration relative to MIC

Question 19

What is the mechanism of action for Chloramphenicol and what coverage does it have?

Answer 19

MOA: 50s ribosomal inhibitor

Coverage: broad-spectrum vs Gram +, Gram - (not pseudomonas), anaerobes, unusual pathogens (Rickettsia, spirochetes, Erhlichia, Coxiella, Typhoid, Salmonella)

Question 20

In what situation is chloramphenicol typically used?

Answer 20

bacterial meningitis in patients with severe beta-lactam allergy

Vancomycin + Chloramphenicol +/- Bactrim (Listeria)

Question 21

What are 3 major toxicities of Chloramphenicol use?

Answer 21

1. bone marrow suppression
2. Aplastic Anemia
3. Gray Baby Syndrome (hypotension, shock, cyanosis)