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Week 6 - Phase 3 > Antibiotics 2 > Flashcards

Antibiotics 2 Flashcards

1
Q

What kinds of ‘inhibitor’ anti-biotics are there?

A

Protein biosynthesis inhibitors
DNA/RNA replication inhibitors
Folate synthesis inhibitors

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2
Q

What protein synthesis inhibitor antibiotics target the 50S ribosome subunit?

A

Macrolides e.g. erythromycin/clarithromycin
Clindamycin
Chloramphenocol

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3
Q

What protein synthesis inhibitors target the 30S ribosomal subunit?

A

Aminoglycosides e.g. Gentimicin.

Tetracyclines e.g. doxycycline.

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4
Q

What bacteria are marcolides (clarythomycin) effective against?

A

Streptococcus, enterococcus, staphylococcus, haemophilus, nisseria.

Also effective against atypcials such as Legionella, mycoplasma, chlamydia.

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5
Q

How is clarthromycin administered?

A

Orally.

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6
Q

What are the adverse effects of clarithromycin?

A
  • Vomiting and diarrhoea
  • QT prolongation
  • Hearing loss with long term use.
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7
Q

What drug interactions are there with clarithromycin?

A
  • Clarithromycin is a cytochrome p450 inhibitor with many drug interactions.
  • Can’t use with simvastatin, atorvastatin or warfarin.
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8
Q

How is clindamycin similar to macrolides?

A
  • same mechanism of action
  • good oral absorption
  • priciple action against gram positives.
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9
Q

How is clindamycin different to macrolides?

A
  • No action against gram-negatives or atypicals.

- Excellent activity against anaerobes.

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10
Q

What antibiotic is used to stop exotoxin production e.g. in necrotising fascitits or toxic shock syndrome?

A

clindamycin

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11
Q

What gut infection are you are risk of when taking clindamycin?

A

C. diff infection.

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12
Q

What are the 4 C’s to avoid use of to prevent C diff?

A

Clindamycin
Co-amoxiclav
Cephalosporins
Ciprofloxacin

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13
Q

What are the toxic effects of Chloramphenicol?

A
  • Bone marrow suppression
  • Aplastic anaemia
  • Optic neuritis
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14
Q

What is chloramphenicol used for?

A
  • Topical therapy to eyes.

- Bacterial meningitis with beta-lactam allergy.

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15
Q

Name an aminoglycoside?

A

Gentamicin

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16
Q

How does gentamicin work?

A

2 mechanisms of action

  1. Reversibly binds to the 30S ribosome. This has a bacteriostatic action and results in prolonged post-antibiotic effect.
  2. Poorly understood action on the cell membrane. This is bacteriocidal. Prominent at high concentrations and results in rapid killing early in dosing interval.
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17
Q

Explain the toxicities of gentomicin?

A
  • Nephrotoxicity
  • Ototoxicity (hearing loss, loss of balance)
  • Neuromuscular blockage, but this is usually only significant in myasthenia gravis
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18
Q

Describe the dosing of gentomicin?

A

Once a day dosing.
Give initial high dose to take advantageof rapid killing.
Leave a long dosing interval of 24-48h to minimise adverse effects.
Only give for 3 days to prevent toxicities developing.

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19
Q

What bacterias is gentomicin used for?

A

staphylocoocus, streptococcus, e coli, coliforms, pseudamonas., haemophilus, nesseria.

20
Q

Give an example of a tetracyclin?

A

Doxycycline.

21
Q

What bacteria is doxycyclin good at treating?

A

Staphylococcus, streptococcus, entrococcus, neisseria, haemophilus.
Atypical such as mycoplasma, chlamydia and coxiella.

22
Q

Why should we avoid tetracyclins in children and pregnant women?

A

Bone abnormailies

Tooth discolouration.

23
Q

What type of antibiotics are Ciprofloxacin and Levofloxacin?

A

Quinolones

24
Q

What route are quinolones administred by?

A

Oral

25
Q

What is ciprofloxacin good for?

A

Good for gram negatives. Commonly used in abdominal infections or UTI.

26
Q

What is levofloxacin good for treating?

A

Respiratory infections. It is good against gram negatives and staph/streptococcus.

27
Q

List toxicities associated with quinolones?

A
  • GI toxicity
  • QT prolongation
  • Tendonitis.
  • C diff infection
28
Q

What is Rifampicin used for?

A

Tuberculosis (in combo therapy)

With another antibiotic in serious gram positive infection (e.g. staph aureus.

29
Q

What interactions does Rifampicin have?

A

It is a potent CYP450 enzyme inducer.

Most drugs that undergo hepatic metabolism affected.

30
Q

Why is TB such a difficult infection to treat?

A

Slow growing bacteria with a high bacterial burden.
Need a long course of antibiotics.
TB can exist in a dormant state.
Can be found in granulomas in the lungs.

31
Q

Describe a short course therapy for TB and what these drugs do?

A

Isoniazid: Bactericidal to mycobacteria.
Rifampicin: Bactericidal against slowly growing organisms in necrotic foci.
Pyrazinamide: Bactericidal, even against slow growing mycobacteria intracellularly.
Ethambutol: Bacteriostatic against slow growing mycobacteria.

32
Q

What are the risks of standard TB therapy?

A

Isoniazid: Hepatotoxicity, peripheral neuropathy.
Rifampicin: liver, bone marrow and renal toxicity.
Pyrazinamide: Hepatitis.
Ethambutol: Optic neuritis.

33
Q

How do inhibitors of folate synthesis work?

A

Inhibition of folate metabolism pathway leads to impaired nucleotide synthesis and therefore impaired DNA replication.

34
Q

Name 2 folate metabolism inhibitors?

A

Trimethoprim

35
Q

How is trimethoprim administered?

A

Orally.

36
Q

What is trimethoprim principally used for?

A

Uncomplicated UTI.

37
Q

What toxicities can occur with trimethoprim use?

A

Elevation of serum creatinine (doesn’t reflect fall in GFR).
Elevation of serum K+ (problematic in patients with renal impairment).
Rash.
GI disturbance.

38
Q

What is co-trimoxazole? What is it used for?

A

Combo antibiotic os trimethoprim and sulphamethoxazole.

Pneumocystis Jirovcii

39
Q

What toxicities occur with co-trimoxazole?

A

Bone marrow suppression

Stevens johnson syndrome.

40
Q

How does metronidazole have its effect?

A

Enters by passive diffusion and produces free radicals which cause damage.

41
Q

When is metronidazole often used?

A

Intra-abdominal infections especially abcesses.

42
Q

What does metronidazole have a reaction with? why?

A

alcohol - causing flushing as you get toxic metabolite build up.

43
Q

Why do we limit metronidazole usage to 2 weeks?

A

Can develop peripheral neuropathy.

44
Q

Describe treatment of an uncomplicated UTI? describe advantages and disadvantages of these treatments?

A

If a lower urinary tract infection with no sepsis or spread to bladder:
Trimethoprim or nitrofuratoin.
Trimethoprim: cant use in 1st trimester of pregnancy as its a folate inhibitor and also has lots of resistance so should only use in really unwell patients. Has good penetration to prostate so good for UTI’s in men.
Nitrofuratoin: good broad spectrum drug. Concentrated in urine so no effects on other tissue. Cause it does this is has no systemic effect, should avoid in renal failure, and can get pulmonary fibrosis with long term use.

45
Q

Why should trimethoprim not be used in pergnancy?

A

As its a folate metabolism inhibitor.

46
Q

What antibiotics are safe in pregnancy?

A

Most Beta-lactams, macrolides and anti-tuberculants.

47
Q

What antibiotics are not considered safe in pregnancy and why?

A

Tetracyclins: Bone and tooth abnormalities.
Trimethoprim: Neural tube defecs in first trimester.
Nitrofurantoin: Haemolytic anaemia in 3rd trimester.
Aminoglycosides: Ototoxicity in 2nd-3rd trimester.
Quinolones: Bone/join abnormalities.

Week 6 - Phase 3 (3 decks)

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