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Antibiotics > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What is an antibiotic?

A

A drug used to treat an infection caused by bacteria

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2
Q

What are the four general mechanisms of antibiotic action?

A

Disruption of bacterial cell wall

Inhibit nucleic acid synthesis

Inhibit protein synthesis

Antimetabolite activity

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3
Q

Which groups of antibiotics mechanism of action is to disrupt the bacterial cell wall?

A

Beta-lactams

  • penicillins
  • cephalosporins
  • carbapenems
  • monobactems

Glycopeptides

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4
Q

How do beta-lactams disrupt the bacterial cell wall?

A

Form covalent bonds with penicillin-binding protein to inhibit final formation of cross links

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5
Q

How do glycopeptides disrupt the bacterial cell wall?

A

Inhibit the release of the building block unit from the cell membrane.

Prevent addition to growing end of the peptidoglycan

Damages cytoplasm

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6
Q

Give examples of penicillins

A

Simple (susceptible to Beta-lactamases):

  • Penicillin V
  • Benzylpenicillin
  • Amoxicillin

Resistant (prevent ring breakdown):

  • Flucloxacillin
  • Co-amoxiclav
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7
Q

What are the uses of simple penicillins?

A

Gram +ve cocci - e.g. streptococcus

Gram -ve cocci/bacilli - e.g. listeria

Spirochetes - e.g. Syphilis

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8
Q

What are the uses of resistant penicillins?

A

Same as simple penicillins, but also for Staphylococcus

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9
Q

What infections can penicillin be used against?

A

RTIs

UTIs

Skin infections

Ear infections

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10
Q

What are the side effects of penicillins?

A

Hypersensitivity ~10% (~0.2% anaphylaxis)

Diarrhoea

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11
Q

Give examples of cephalosporins

A

1st generation

  • Cephradine
  • Cephalexin

2nd generation
- Cefuroxime

3rd generation

  • Cefotaxime
  • Ceftriaxone
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12
Q

What are the side effects of cephalosporins?

A

Similar to penicillin

i.e. hypersensitivity, diarrhoea

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13
Q

Which cephalosporin would be used to treat meningitis?

A

Cefotaxime (3rd)

Ceftriaxone (3rd)

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14
Q

Which cephalosporin would be used to treat pseudomonas?

A

Ceftriaxone (3rd)

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15
Q

Which cephalosporin would be used to treat community acquired meningitis?

A

Cefuroxime (2nd)

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16
Q

Which cephalosporin would be used to treat skin/soft tissue infection?

A

Cephradine (1st)

Cephalexin (1st)

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17
Q

Give an example of a glycopeptide?

A

Vancomycin

not absorbed orally, althought can treat GIT infection

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18
Q

Which conditions might you use glycopeptides for?

A

MRSA

Resistant C. Difficile

(Usually administered I.V. - not absorbed otherwise)

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19
Q

What are the side effects of Glycopeptides?

A

Ototoxic - ear and its nerve supply

Nephrotoxic - kidneys

“Red Man Syndrome” - Hypersensitivity reaction

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20
Q

Which groups of antibiotics mechanism of action is to inhibit nucleic acid synthesis?

A

Quinolones

Metranidazole

Rifampicin

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21
Q

Which groups of antibiotics mechanism of action is to inhibit protein synthesis?

A

Macrolides

tetracyclines

Aminoglycosides

Chloramphenicol

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22
Q

Which groups of antibiotics mechanism of action is antimetabolite activity?

A

Trimethoprim

Sulphonamides

23
Q

How do quinolones inhibit nucleic acid synthesis?

A

Inhibit DNA gyrase enzyme to prevent supercoiling of bacterial DNA

24
Q

Give examples of quinolones

A

Ciprofloxacin

Levofloxacin

i.e. -oxacin

25
Q

How does metranidazole inhibit nucleic acid synthesis?

A

Damage DNA by forming reactive intermediates that inhibit DNA synthesis

26
Q

How does rifampicin inhibit nucleic acid synthesis?

A

Inhibit RNA polymerase to prevent transcription of mRNA

27
Q

What are Quinolones used for?

A

Broad spectrum antibiotic, although usually 2nd line

Especially used against pseudomonas
- only oral Abx that works

28
Q

What can inhibit the absorption of quinolones?

A

Metals

29
Q

What are the contraindications and interactions of quinolones?

A

CI:

  • Epilepsy - reduces seizure threshold
  • Children

Interactions:
- Warfarin

30
Q

What is metranidazole used for?

A

Effective against anaerobes

Abdo, GI and Perineal infections

31
Q

What are the side effects / interactions of Metranidazole?

A

Alcohol interaction

  • Vomiting
  • tachycardia
  • dyspnoea
32
Q

What is Rifampicin used for?

A

Used in Mycobacteria, especially Tuberculosis (RIPE - used in combo)

33
Q

What are the side effects / interactions of Rifampicin?

A

Induces P450s
- Th. any drugs that are metabolised by P450s have increased efficacy

Stains contact lenses orange

34
Q

How do macrolides inhibit protein synthesis?

A

Binds to 50S subunit and inhibits translocation (where tRNA in A site is moved along to the P site)

35
Q

How do tetracyclines inhibit protein synthesis?

A

Binds to the 30S subunit of the ribosome.

Actively competes with the tRNA for the A site to inhibit its binding.

36
Q

How do aminoglycosides inhibit protein synthesis?

A

Binds to 30S subunit of the ribosome.

Causes misreading of codon on the mRNA, resulting in non-functional proteins produced

37
Q

How does chloramphenicol inhibit protein synthesis?

A

Inhibits transpeptidation (where the growing peptide chain attached to the P site is transferred to the amino-acid attached to tRNA in A site)

38
Q

Give examples of macrolides

A

Erythromycin

Clarithromycin

39
Q

Give examples of tetracyclines

A

Doxycycline

Oxytetracycline

Tetracycline

40
Q

Give examples of aminoglycosides

A

Gentamicin

Tobramycin

Amikacin

41
Q

Which antibiotics are used as a penicillin replacement?

A

Macrolides

42
Q

What are the indications of macrolides?

A

Substitute for penicillin = similar effects

More SE though

43
Q

What are the side effects/interactions of macrolides?

A

Inhibit liver metabolism of warfarin and statins
=> may induce OD on these drugs - withhold statins

Diarrhoea and Vomiting

44
Q

What are the indications of tetracyclines?

A

Skin/soft tissue infection (mostly)

Acne

45
Q

What are the side effects of tetracyclines?

A

Photosensitivity

46
Q

What are the interactions of tetracyclines?

A

Children, Pregnancy, Breastfeeding

- Incorporated into bone/teeth = causes discolouration and growth stunting

47
Q

What are the indications of aminoglycosides?

A

RTIs and tuberculosis

administered IV only

48
Q

Waht are the side effects of aminoglycosides?

A

Oxotoxicity (Ear) - especially in elderly

Nephrotoxicity (Kidney)

49
Q

What is the action of trrimethoprim?

A

Inhibits the usage of folate

50
Q

What is the action of sulphonamides?

A

Inhibit mechanism of folate synthesis

51
Q

What are the indications for trimethoprim?

A

Used mostly in UTIs

- Excreted unchanged in high quantities in urine

52
Q

What are the side effects of trimethoprim?

A

Rare but serious side effects therefore only if risk-benefit balance is good

53
Q

Which antibiotics should be used for infection as a result of stones?

A

IV Ampicillin

IV Gentamicin

Antibiotics (1 decks)

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