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BSMS308 > 7. Antibiotics > Flashcards

7. Antibiotics Flashcards

1
Q

How much of antibiotic use is inappropriate?

A

50% of antbiotic therapy - baring in mind 25% of inpatients are on antibiotics and 2/3 will be put on antibiotics at some stage

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2
Q

Antibiotic misuse and relationship consequences

A

MRSA, VRE
C. diff
Resistant Enterobacteriaceae esp E. coli and K. pneumonieae
- Extended spectrum Beta-lactamase (ESBL) producers
Carbapenemase producing enterobacteriaceae (CPE)
Klebsiella producing carbapenemases (KPC)

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3
Q

Does antibiotic use affect patients on an individual basis

A

places individual patients at risk of resistant infection - including UTIs and RTIs

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4
Q

key agents which bacteria can be resistant to?

A

co-amoxiclav, ciprofloxacin, piperacillin-tazobactam, gentamicin

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5
Q

Which bacteria are antibiotic resistances most common in?

A

Gram negatives like E. coli

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6
Q

Principles of safe and rational prescribing of antibiotics - the initial prescribing decision

A

Microbial aetiology - where the infection is, where they caught it (hosp vs community) - focus and exposure

Antimicrobial resistance - epidemiology and exposure

Patient factors - predisposition and severity

Antibiotic knowledge

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7
Q

Rational use of antibiotics demands consideration of:

A

The aetiological agent (AMR potential)

The patient

The drug (mechanism of action-> spectrum of activity
mechanisms of resistance
key pharmacology

Monitoring

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8
Q

What is antimicrobial stewardship?

A

Using antibiotics wisely and responsibly taking into account the long-term effects of antimicrobial selection, dosage, and duration of treatment on resistance developing

Key feature of health policy in the NHS
enforced by the 2008 health and social care act

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9
Q

Aims of antimicrobial stewardship

A

enhance health outcomes
reduce antibiotic resistance
decrease unnecessary costs

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10
Q

What is TARGET?

A

An Antibiotics toolkit that helps to influence prescribers’ and patient’s personal attitudes, social norms and perceived barriers to optimal antibiotic prescribing

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11
Q

Are inpatients or outpatients more at risk from infection?

A

Inpatients, need to be especially on the lookout for prompt recognition and treatment of sepsis

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12
Q

Sepsis signs

A 
Systolic BP <90mmHg
Lactate >2mmol/l
Heart rate > 130 per minute
Resp rate>25 per mintue
O2 sats <91%
Responds only to voice or pain/unresponsive
purpuric rash
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13
Q

Sepsis treatment

A

Give IV antibiotics in the first hour according to trust policy (TAKE ALLERGY HX FIRST)

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14
Q

Start smart part of start smart then focus

A

Do not start antibiotics in absence of clinical evidence of bacterial infection
Take drug allergy hx, give w/i 1 hour of infection, local antimicrobial guidelines, document clinical indication, dose and route on drug chart and in notes, include duration and review/stop date, obtain cultures before therapy

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15
Q

Focus part of start smart then focus

A

Clinical review & decision after 48-72 hours
Clinical review, check micro and make clear plan, document the decision

  1. Stop
  2. Switch IV to oral
  3. Change antibiotic
  4. Continue
  5. OPAT (outpatient parenteral antibiotic therapy)

Document all decisions

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16
Q

Drivers to stop antibiotics

A

Toxicity

Risk of AMR

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17
Q

Drivers to continue antibiotics

A

Personal responsibility
Reluctance to interfere
patient outcome

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18
Q

Most common outcome of focussing antibiotics?

A

95% of review and revise decisions are to continue Abx treatment

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19
Q

Things to keep in mind when you review?

A

Remember antibiotics are harmful?
Did they ever have an infection?
Are they better now?
Do the risks of continuing outweigh the benefits?

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20
Q

Key points about rational antibiotics antibiotic prescribing decisions

A

Two moments

  1. Initial prescription:
    - microbial aetiology
    - patient factors
    - antimicrobial resistance issues
    - knowledge
    - guidelines - choice of agent, duration of therapy
  2. Review and revise
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21
Q

Amoxicillin

A

An aminopenicillin

particularly strong against Gram negative bacteria

used to treat S. pyogenes infections (sore throat, skin infections), pneumococcal infections(RTIs), coliform/UTI

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22
Q

Mechanism of action of amoxicillin

A

Inhibition of bacterial cell wall synthesis

23
Q

Standard dose of amoxicillin, side effects and drug interactions

A

250-1000mg 8 hourly

allergy, damage to commensal microflora

Interactions: can increase levels of other protein bound drugs

24
Q

Amoxicillin

A 
good oral bioavailability
Protein binding 20%
Metabolism not significant
Half-life 1 hour
Excretion 1 hour
25
Q

Beta-lactam antibiotics

A

Penicillins - penicillin G, penicillin V, Amoxicillin, coamoxiclav, flucloxacillin, piperacillin

Cephalosporins e.g. cephalexin and cefuroxime

carbapenams e.g. meropenem

26
Q

the easy oral pencillin

A

Amoxicillin

27
Q

Amox protected against beta-lactamases

A

co-amoxiclav

28
Q

The penicillin for Staph aureus

A

flucloxacillin

29
Q

Penicillin for pseudomonas

A

piperacillin

30
Q

Beta lactam allergy

A 
Penicillin allergy - a class effect
- immediate/ accelerate - type 1 (0.02% of courses)
Delayed - mixed mechanism (2-3% of courses)
31
Q

Type 1 penicillin allergy

A

Immediate - 0-72hrs after exposure
IgE mediated, mast cell mediated
Urticaria, wheeze, life threatening
0.02% of courses

32
Q

Delayed penicillin allergy

A

2-3% of courses
>72 after exposure
Will worsen with repeated exposure
does not become immediate type

33
Q

Cephalosporin allergy

A

Very complicated - lots of potential haptens involved
Not a class effect
Penicillin X-reactivity more with 1st and 2nd generations
Risk ~8% if previous penicillin allergy
Less with 3rd generation

34
Q

History of beta-lactam allergy

A

When was it?
What happened - time course and severity?
What was the drug?
Might they have had glandular fever?
Have they had a different beta lactam since?

good history of anaphylaxis - avoid all beta lactams
Weak history or of delayed reaction - consider rechallenge

35
Q

Clarithromycin

A

Macrolide w similar spectrum of action to amoxicillin
Used for pts with penicillin allergy to treat S. pyogenes infections (sore throat and skin infections)
pneumococcal infections (respiratory tract)
coliform infections (UTIs)

Also against cell-wall deficient bacteria e.g. chlamydia which causes penumonia and GU infections

36
Q

Clarithromycin pharmacokinetics

A 
Good oral bioavailability
high protein binding
hepatic metabolism
1-6 hours half
Excretion as metabolites in bile
37
Q

Clarithromycin mechanism of action

A

inhibition of protein synthesis bacterial ribosome (50s subunits)

38
Q

Adverse effects and interactions of clarithromycin

A

Nausea and diarrhoea, may alter cardiac conduction - arrhythmias

interactions - inhibits enzymes (cytochrome p450 enzymes) involved in the metabolism of other drugs

39
Q

Standard dose of clarythromycin

A

500mg 12 hourly

40
Q

Vancomycin

A

a glycopeptide active only against Gram-positive bacteria and is active against resistance strains including MRSA

41
Q

Vancomycin pharmacokinetics

A 
V low oral bioavailability 
50% protein binding 
No metabolism
4-8 hours half life
Excreted as urine
42
Q

Mechanism of action of vancomycin

A

inhibits bacterial cell wall (peptidoglycans) formation by a different target to beta lactams

43
Q

Standard dose

A

500-1500mg 12 hourly
Narrow therapeutic window (levels needed to kill the bacteria v close to level toxic to pt)

Dose by drugs level in blood

44
Q

Adverse effects and interaction

A

Nephrotoxic and ototoxic

Interacts w other ototoxic and nephrotoxic drugs

45
Q

Doxycycline

A

A tetracycline w good activity against Gram positive e.g. Streps and Staphs
against some Gram negs e.g. haemophilus

Active against cell-wall deficient bacteria e.g. chlamydia which cause pneumonia and genitourinary infections

Poor against Enterobacteriaceae, anaerobes

Used for skin, resp tract, genital tract infections

Loe C diff risk

46
Q

Mechanism of action of doxycycline

A

Inhibition of protein synthesis in the bacterial ribosome (30s subunit)

47
Q

Adverse effects and interactions of doxycycline

A

Dyspepsia, photosensitivity, avoid in pregnancy/children (teeth)
Interactions: competes for protein binding - warfarin, digoxin etc

48
Q

Doxycycline

A 
good oral bioavaialbity
Moderate protein binding
No metabolism
Half-life 6-12 hours
Excreted in urine and bile
49
Q

Standard dose of doxycycline

A

100-200mg daily

50
Q

Nitrofurantoin

A

Only nitrofuran

Wide spectrum - esp E. coli and other enterobactericeae, enterococci, staphs, some streps
Use for lower UTIs only too little tissue penetration elsewhere

51
Q

Mechanism of action of nitrofurantoin

A

complex. Damages bacterial DNA

High resistance threshold

52
Q

Adverse effects of nitrofurantoin

A

V well tolerated
Safe in early pregnancy - avoid late
Avoid in renal impairment - peripheral neuropathy, doesn’t uterine if eGFR low

no major interactions

53
Q

Standard dose of nitrofurantoin

A

50mg qds

BSMS308 (9 decks)

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