Antibiotics: Protein Synthesis Inhibitors

Question 1

What are the 5 main categories of antibiotic?

Answer 1

Cell wall inhibitors
Protein biosynthesis inhibitors
DNA/RNA replication inhibitors
Folate synthesis inhibitors
Special cases

Question 2

What are the 2 groups of protein biosynthesis inhibitors? List which types of antibiotics are found in each group. (5 in total)

Answer 2

Antibiotics targeting the 50S ribosome subunit:

1. Macrolides
2. Clindamycin
3. Chloraphenicol

Antibiotics targeting the 30S ribosome subunit:

1. Aminoglycosides
2. Tetracyclines

Question 3

List 3 examples of macrolides.

Answer 3

Erythromycin
Clarithromycin
Azithromycin

Question 4

How are macrolides administered?

Answer 4

Oral

Question 5

Describe the mechanism of action of macrolides. (2)

Answer 5

1. Bind to the 50S subunit of bacterial ribosomes, inhibiting ribosome function
2. Therefore bacteria can’t produce proteins

Question 6

Which 2 types of protein synthesis inhibitors are used for atypical bacteria?

Answer 6

Macrolides

Tetracyclines

Question 7

List 3 adverse effects of macrolides.

Answer 7

Diarrhoea & vomiting
QT prolongation
Hearing loss (long term use)

Question 8

Give 3 examples of drug interactions for macrolides.

Answer 8

Simvastatin
Atorvastatin
Warfarin

Question 9

How is clindamycin administered?

Answer 9

Oral

Question 10

Describe the mechanism of action of clindamycin. (2)

Answer 10

1. Bind to the 50S subunit of bacterial ribosomes, inhibiting protein synthesis
2. Inhibit exotoxin production
   a. Therefore used in toxin-mediated disease, e.g. toxic shock syndrome, necrotising fasciitis

Question 11

Which 6 infections is clindamycin used for?

Answer 11

Bacteriodes
Clostridium
Streptococcus
Staphylococcus

Infections causing toxin-mediated disease, i.e.

1. Toxic shock syndrome
2. Necrotising fasciitis

Question 12

List 1 adverse effect of clindamycin.

Why is this common with this drug?

Answer 12

C. difficile infection

WHY? Clindamycin is particularly active against anaerobes, e.g. colonic microflora

This disrupts normal microflora, allowing C. diff infection

Question 13

What are the 4Cs associated with C. difficile infection?

Answer 13

Clindamycin
Co-amoxiclav
Cephalosporins
Ciprofloxacin

NOTE: all antibiotics can cause C. diff, but these are especially bad

Question 14

How is chloramphenicol administered?

Answer 14

Oral or IV

Question 15

Describe the mechanism of action of chloramphenicol. (2)

Answer 15

1. Binds to the 50S subunit of bacterial ribosomes

2. This inhibits bacterial protein production

Question 16

List 3 adverse effects of chloramphenicol.

Answer 16

Bone marrow suppression
Aplastic anaemia
Optic neuritis

Question 17

Which 2 conditions is chloramphenicol used for?

Answer 17

Topical therapy in eye infections

Bacterial meningitis with beta-lactam allergy

Question 18

Give 1 example of an aminoglycoside antibiotic.

Answer 18

Gentamicin

Question 19

How are aminoglycosides administered?

What is the maximum duration of treatment?

List 3 dosing requirements for aminoglycosides.

Answer 19

IV

Maximum duration: 3 days

Dosing requirements:

1. High loading dose
2. Long dosing intervals (24-48 hours)
3. Monitoring of trough level

Question 20

Describe the mechanism of action of aminoglycosides. (3)

Answer 20

1. Reversibly binds to 30S subunit of bacterial ribosomes
2. This causes bacteriostatic action
   b. This causes prolonged post-antibiotic effect
3. Bactericidal action on cell membrane
   a. Rapid bacteriolysis

Question 21

List 3 adverse effects of aminoglycosides.

Answer 21

Nephrotoxicity
Ototoxicity (hearing loss, loss of balance, oscillopsia)
Neuromuscular blockade

Question 22

List 1 example of a tetracyclin antibiotic.

Answer 22

Doxycycline

Question 23

How is doxycycline administered?

Answer 23

Oral

Question 24

Describe the mechanism of action of tetracyclines. (1)

Answer 24

1. Target 30S subunit of bacterial ribosomes, inhibiting protein synthesis

Question 25

List 2 adverse effects of tetracyclines.

Which patient groups would you avoid giving tetracyclines?

Answer 25

Bone abnormalities
Tooth discolouration

AVOID IN:
Pregnant women
Children