Antibiotics

Question 1

What does therapeutic index means with regards to antibiotics? [1]

What’s the difference between a high and low therapeutic index? [1]

Answer 1

The therapeutic index of an antibiotic is determined by comparing the minimum effective concentration (MEC) required to inhibit or kill the pathogenic bacteria causing the infection with the minimum toxic concentration (MTC) that can cause harm to the patient.

High therapeutic index:
- Indicates that the antibiotic can effectively target and eliminate the bacteria causing the infection while minimizing the risk of adverse effects or toxicity to the patient

Low therapeutic index:
- suggests that the antibiotic may have a narrow margin of safety, meaning there is a higher risk of toxicity or adverse effects even at therapeutic doses.

Question 2

Answer 2

Question 3

Which antibiotics target bacterial cell wall synthesis? [2]

What is the specific site of action? [1]

Answer 3

Beta lactams
- penicillins
- cephalosporins (e.g. ceftriaxone)
- carbapenems (e.g. Doripenem),
- aztreonam

Glycopeptides
- vancomycin and teicoplanin

Work at site of peptidoglycan cell wall

Question 4

Give three examples of what penicillins used to treat? [3]

Answer 4

Meningitis
Pneumonia & Resp infections
Syphilis

Question 5

State some known issues of penicllin use [3]

Answer 5

• Resistance (e.g. from staphylococcus)
• Allergies
• Cross-hypersensitivty with cephalosporins

Question 6

Which agents inhibit bacterial protein synthesis? [5]

Answer 6

Aminglycosides - e.g. gentamicin, amikacin, tobramycin, neomycin, and streptomycin.
Tetracyclines e.g. doxycycline
Chloramphenicol
Macrolides - e.g erythromycin and clarithromycin
Clindamycin
Fusidic acid

Question 7

All of the following work to inhibit protein synthesis. However, which is the only agent that is bactericidal?

Aminglycosides
Tetracyclines
Chloramphenicol
Macrolides
Clindamycin
Fusidic acid

Answer 7

Aminglycosides - e.g. amakacin

Question 8

How do aminoglycosides spefiically work? [1]

Answer 8

Inhibition of 30S ribosomal subunit

Question 9

What are key adverse effects of aminoglycoside (e.g. amakacin) use? [3]

Answer 9

Otoxicity
Nephrotoxicity
Contraindicated in pregnancy

Question 10

Give four side effects of macrolide (e.g. azithromycin) use

Answer 10

• N&V, diarrhoea
• Abdominal pain
• Liver toxicity
• Prolonged QT

Question 11

Which drug is often used after surgery to increase gut motility? [1]

Answer 11

Erythromycin

Question 12

Quinolones (e.g. ciprofloxacin), rifampicin and metronidazole all work as what general MoA? [1]

Answer 12

Affect nucleic acid metabolism

Question 13

What are 4 key adverse effect of fluoroquinolones (e.g. flucoxacillin)? [4]

Answer 13

• Tendon rupture
• Children
• Reduces seizure threshold
• Prolongs QT intervals
• Photosensitivity
• Bad for pregnant

Question 14

Sulphonamides and trimethoprim work by which MoA? [1]

Answer 14

Anti-folates

Question 15

Amphotericin, colisitn and daptomycin all work by which MoA? [1]

Answer 15

Membrane disorganising agents

Question 16

Is benzyl penicllin broadly gram +ve or -ve? [1]

Answer 16

Gram negative

Question 17

Name two anti-biotics that have the greatest spectrum in coverage

Answer 17

Meropenum/Imipenem
Piperacillin-Tazobactam
Cefrtiaxone
Cefuroxime

Question 18

Name two antibiotics that work purely as gram positive coverage [2]

Answer 18

Vancomycin/Teicoplanin
Flucloxacillin
Benzyl Penicllin

Question 19

Describe co-amoxiclav’s coverage [1]

Answer 19

Mostly gram+ve, with a bit of gram -ve

Question 20

Metronidazole is particularly good at covering which type of microbes? [1]

Answer 20

Anaerobes

Question 21

Fluconazole, viroconazole, miconazole are which type of drug class? [1]

Answer 21

Antifungals