Antibiotics

Question 1

List 3 classes of drug which inhibit bacterial protein synthesis

Answer 1

• Aminoglycosides
• Tetracyclines
• Macrolides

Question 2

Give 2 classes of drug (and sub-classes if relevant) which inhibit bacterial cell wall synthesis

Answer 2

• Beta-lactams - penicillins and cephalosporins

- Glycopeptides

Question 3

Give a drug class which inhibits bacterial nucleic acid synthesis

Answer 3

Quinolones

Question 4

List some uses of Aminoglycoside antibiotics

Answer 4

Severe infections caused by Gram negative aerobic bacteria

Question 5

Give 2 examples of Aminoglycoside antibiotics

Answer 5

• Gentamicin

- Neomycin

Question 6

What is the mechanism of action of Aminoglycosides?

Why are they specific to aerobic bacteria?

Answer 6

Bind to 30S subunit of bacterial ribosome - prevent protein synthesis.
Require oxygen-driven transport system to enter cell

Question 7

List 2 important ADRs of Aminoglycosides, and therefore a DDI

Answer 7

Ototoxicity - worse with loop diuretics

Nephrotoxicity

Question 8

How is Gentamicin administered?

Answer 8

IV only

Question 9

Name 3 examples of tetracyclines

Answer 9

Tetracycline
Doxycycline
Oxetetracycline

Question 10

Give some uses for tetracyclines

Answer 10

Acne
LRTIs
Chlamydia

Question 11

What is the mechanism of action of tetracyclines?

Answer 11

Inhibit bacterial protein synthesis by binding to 30S subunit of bacterial ribosome

Question 12

Give two macrolide antibiotics

Answer 12

Erythromycin

Clarithromycin

Question 13

What is the mechanism of Macrolides?

Answer 13

Bind to 50S subunit of bacterial ribosome - inhibit protein synthesis

Question 14

Give 4 ADRs of macrolides

Any DDIs?

Answer 14

GI irritant
Allergy
Antibiotic-associated colitis
Prolong QT
DDIs - Inhibit CYP, and caution with other drugs prolonging QT

Question 15

Give 3 examples of Cephalosporin antibiotics

Answer 15

Cefaclor
Cefotaxime
Aztreonam
(Ceftriaxone but not on list)

Question 16

What are Cephalosporins used for?

Answer 16

Oral = 2nd or 3rd line treatment for urinary and resp tract infections
IV only for very serious infections

Question 17

What is the mechanism of Cephalosporins?

Answer 17

Inhibit enzyme responsible for cross-linking peptidoglycans in bacterial cell walls - weakens wall - cannot maintain osmotic gradient - lysis - death.

Question 18

List 3 ADRs of Cephalosporins

Answer 18

GI upset
Hypersensitivity
Risk of CNS toxicity

Question 19

Why is Warfarin not good with Cephalosporins?

Answer 19

Cephalosporins destroy gut bacteria responsible for making vitamin K, therefore clotting not as good anyway - warfarin may cause big bleed

Question 20

Name 4 examples of penicillin-based drugs

Answer 20

• Penicillin
• Amoxicillin
• Flucloxacillin
• Co-amoxiclav

Question 21

What is special about co-amoxiclav?

Answer 21

Combination of amoxicillin and clavulanic acid

Clavulanic acid inhibits B-lactamases, so prevents breakdown of amoxicillin

Question 22

Which drug shouldn’t be given with penicillins?

Answer 22

Methotrexate - increased risk of toxicity

Question 23

Which class of drug does Vancomycin belong to?

Answer 23

Glycopeptides

Question 24

What is Vancomycin used for?

Answer 24

Gram +ve infection if severe/resistant to/allergic to penicillin
C diff infection (2nd line after metronidazole)

Question 25

Give 4 important ADRs of Vancomycin

Answer 25

Thrombophlebitis at injection site
Red man syndrome - pseudo-anaphylaxis
Ototoxicity
Neutropenia

Question 26

What is the antibiotics regime in TB?

Answer 26

• Rifampicin, Isoniazid, Pyrazinamide and Ethambutol for 2 months
• R + I for a further 4 months

Question 27

Give an ADR of each TB drug (and DDI where appropriate)

Answer 27

• Rifampicin - orange secretions and interferes with OCP
• Isoniazid - Dry mouth
• Pyrazinamide - Hepatotoxicity
• Ethambutol - optic neuritis