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Drugs > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

Name 2 penecillins

A

Benzylpenecillin (IV/IM) phenoxylmethopenecillin

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2
Q

What are the mechansims by which penicillins work?

A
  • Blocks transpeptidase enzyme responsible for cross linking peptidoglycans in bacterial cell wall
  • Weakens walls and reduces ability to maintain osmotic gradient
  • Swelling, lysis, and cell death
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3
Q

What component of the penicillin is responsible for their microbial action

A
  • Beta-lactam ring- side chains attached which determines in microbrial spectrum and properties
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4
Q

What are the resistance mechanisms against penicillins?

A

Beta lactamase - break down B-lactam rings
Reduces permeability to penecillins and increased extrusion
Change target enzyme

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5
Q

What are the indications for penicillins?

A

Streptococcal infections - tonsillitis, middle ear infection, pneumonia (+ macrolide), endocarditis, soft tissue/skin infection (+fluclox if severe),

Clostridium infection e.g. tetanus

Meningococcal infection e.g. meningitis, septicaemia

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6
Q

What are the CIs for penicillins?

A
  • usually well tolerated and safe
  • Dose reduction in renal impairment
  • Current C Diff infection
  • Penecillin allergy
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7
Q

What are the SEs for penicillin?

A

Allergic reaction (1-10% population)

  • Skin rash - subacute (delayed) IgG mediated reaction - occurs 7-10 days post 1st exposure and after 1-2days repeated exposure
  • Anaphylactic reaction - immediate life threatening IgE reaction - mins-hours after exposure - hypotension, brochospasm/oedema, angioedema
  • High doses/renal impairment - CNS toxicity - convulsions/coma
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8
Q

What are the interactions of penicillin?

A

Reduces renal excretion of methotrexate - increased toxicity

Warfarin - enhances anticoagulation

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9
Q

Name one penicillinase/beta-lactamase resistant penicillin?

A

Flucloxacillin

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10
Q

What is the mechanism by which fluxcloxacillin resists Beta lactamase

A

Contains acyl side chain which protects flucloxacillin from beta lactamase - effective against beta lactamase producing staphylococcal infections

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11
Q

What are the indications for flucloxaccillin

A
  1. Skin and soft tissue infections e.g. cellulitis (+ benzylpenecillin if severe)
  2. Osteomyelitis/septic arthritis
  3. Other e.g. endocarditis
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12
Q

What 2 antibiotics make up Tazocin?

A

Tazobactam + piperacillin

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13
Q

What is Tazocin indicated for?

A
  • Anti-pseudomonal
  • Hopsital acquired pneumonia
  • Urinary tract infection (complicated)
  • Septicaemia
  • Peritonitis
  • Soft tissue and skin infection (Staph aureus)
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14
Q

What are the SEs of tazocin?

A
  • GI upset
  • ABx associated colitis (C Diff)
  • Hypersensitivity
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15
Q

What are the broad spectrum penecillins?

A
  • Amoxicillin

- Co-amoxiclav

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16
Q

What is co-amoxiclav made up of?

A

amoxicillin + clavulanic acid (increases spectrum to include beta lactamase producing bacteria e.g. staphylcoccus aureus, gram- anaerobes )

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17
Q

What are the indications for the broad spectrum penecillins (co-amoxiclav/amoxicillin)

A
  1. Empirical Tx for community acquired pneumonia (e.g. strep pneu) or gram- (e.g. H influ) bacteria
  2. Empirical Tx for urinary tract infections e.g. E Coli
  3. Tx for hospital acquired infection or intra-abdominal sepsis, caused by gram-, anaerobic pathogens, or ABx resistant
  4. Combo Tx for H Pylori peptic ulcer
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18
Q

Name 2 cephalosporins and carbapenems

A

Cephradine, Cefalexin

Meropenem, Ertapenem

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19
Q

What is the mechanism by which cephalosporins/carbapenems exert their action?

A

BROAD SPECTRUM

  • Inhibit transpeptidase responsible for the cross-linking of peptidoglycan in bacterial cell wall
  • Weakens cell wall and reduces cell ability to maintain osmotic gradient
  • Cell swelling > lysis > cell death
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20
Q

What structural properties make cephalosporins and carbapenems more resistant to beta lactamases than vs penecillin?

A

Cephalosporin - Dihydrothiazine ring on beta lactam ring

Carbapenem -Hydroxyethyl side chain on beta lactam ring

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21
Q

What are the indications for cepahlosporins/carbapenems?

A

Oral cephalosporins - 2nd line and 3rd line for UTIs and respiratory tract infection

IV carbapenems and cephalosporins - reserved for severe, hospital acquired infections, complicated UTIs, septicaemia, intraabdominal sepsis, soft and skin infections

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22
Q

What are the SEs of cephalosporins/carbapenems?

A
  • GI upset
  • Hypersensitivity
  • CNS toxicity - seizures/coma - high doses or with renal impairment
  • ABx associated colitis (C Diff)
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23
Q

What are the CIs for carbapenems/cephalosporins?

A
  • Risk of C Diff infection
  • Caution in epilepsy
  • Hypersensitivity (beta lactam ring)
  • Renal impairment - reduce dose
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24
Q

What are the potential interactions of cephalosporins/carbapenems?

A
  • Reduce efficacy and plasma concentration of sodium valporate
  • Enhanced anticoagulative effect of warfarin- Kills of floral bacteria responsible for synthesising vitamin K -
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25
Q

What is the mechanism by which trimethoprime exerts its action?

A
  • inhibits bacterial folate metabolism - slows bacterial growth (bacteriostatic)
  • Broad spectrum - gram +/- bacteria (especially enterobacteria e.g. E Coli) - however, widespread resistance
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26
Q

What are the indications for trimethoprine?

A

1st line for uncomplicated UTI infection (nitrofurantoin/amoxicillin = alternatives)

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27
Q

What are the CI for trimethoprine?

A
  • 1st trimester in pregnancy - folate antagonist - results in neural tube/cranial defect
  • Folate deficiency - may worsen haematological defects
  • Renal impairment - excreted unchanged = good for UTI, not so good for renal impairment
  • Adverse effects more in neonates, elderly and HIV sufferers
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28
Q

What are the SEs for trimethoprine?

A
  • GI upset
  • Skin rash/hypersensitivity reactions e.g. anaphylaxis, drug fever, erythema multiform
  • Haematological defects - folate antagonist (leucopenia, thrombocytopenia)
  • Hyperkalaemia and increased serum creatine
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29
Q

What are the potential interactions for trimethoprine?

A
  • K+ elevating drugs e.g. aldosterone antagonists, ACEi, AT1 blockers could precipitate hyperk+
  • Enhances anti-coagulation of warfarin by killing off Vit K synthesising bacteria
  • Drugs that antagonise folate (e.g. methotrexate) or increase folate metabolism (e.g. phenytoin) increase susceptibility to haematological disorders
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30
Q

What is the mechanism by which nitrofurantoin exerts its action?

A

Metabolised by nitrofuran reductase. Active metabolites damage bacterial cell DNA - bacteriocidal

31
Q

What bacteria is nitrofuratoin active against?

A

Gram- (E Coli) and gram+ (Staph caprophyticus) - commonly cause UTI

32
Q

What are the resistance mechanisms against nitrofurantoin?

A

Lower nitrofuran reductase

33
Q

What are the indications for nitrofurantoin?

A
  1. 1st line for uncomplicated UTI (alternative = trimethoprin, amoxicillin)
34
Q

What are the CIs for nitrofurantoin?

A
  • Pregnant women coming towards term
  • Babies <3 months old
  • Renal impairment - reduces efficacy and increases risk of SE
  • Long term prevention of UTI - increases risk of SE, especially elderly
35
Q

What are the SEs of nitrofurantoin?

A
  • GI upset
  • Hypersensitivity - delayed/immediate
  • Turn urine green/yellow/brown - temporary
  • Pulmonary (fibrosis, pneumonitis), hepatic and peripheral neuropathy
  • Haemolytic anaemia in neonates - immature RBCs damaged by nitrofuratoin produced superoxides
36
Q

Name 2 tetracyclines

A

Doxycycline, lymecycline

37
Q

What is the mechanism by which tetracyclines work?

A

Prevents bacterial protein synthesis

Bind to 30S subunit of ribosome. Prevents binding of tRNA to mRNA - prevents AA binding to polypeptide chain

38
Q

What are the indications for tetracycline?

A
  1. Acne vulgaris
  2. LRTI - COPD exacerbation, pneumonia, atypical pneumonia
  3. Chlamydial infection and inflammatory pelvic disease
  4. Others: malaria prophylaxis, lyme disease, anthrax, typhoid
39
Q

What are the CIs for tetracyclines?

A
  • Binds to developing bones and teeth. Contraindicated in pregnancy, breastfeeding and children <12 yrs
  • Renal impairment - reduces efficacy and increases risk of toxicity
40
Q

What are the SEs of tetracyclines?

A
  • GI upset
  • Hypersensitivity - delayed/immediate
    Tetracycline specific:
    • Oesophageal irritation, ulceration, dysphagia
    • Discolouration and hypoplasia of tooth enamel
    • Photosensitivity
    • Cranial hypertension (rare - headache/visual
      disturbance)
41
Q

What are the Interactions of tetracyclines?

A
  • binds to divalent cations - take 2hrs after ingesting calcium, anatacids and iron - otherwise, absorption impaired
  • Kills off Vit K synthesising bacteria - enhance anticoagulant effect of warfarin
42
Q

Name one aminoglycoside

A

Gentamicin

43
Q

What is the mechanism by which aminoglycosides/gentamicin works?

A
  • Blocks ribosome subunit 30S (reduces bacterial protein synthesis) and bacteriocidal by unknown mechanism
  • Dependent on O2 dependent transport system
  • Effective against gram - aerobes and staphylococcal but NOT anaerobes/streptococcus
44
Q

What are the indications for gentamicin?

A

Severe life threatening infection - mainly by gram- aerobic species e.g. Pseduo. aeruginosa

  1. Severe sepsis
  2. Pyelopheritis/complicated UTI (e.g. prostatis)
  3. Biliary/intra-abdominal sepsis
  4. Endocarditis
    5
45
Q

What are the SEs of gentimicin?

A
  • BInd to tubular epithelial cells in kidney and vestibular/cochlear hair cells
  • Nephrotoxic - increased serum urea and creatinine, reduced urine
  • Ototoxic - hearing loss, tinnitus, vertigo
46
Q

What are the CIs for gentamicin?

A
  • Monitor plasma levels of gentamicin to prevent damage to kidney/cochlear/vestibular system, particularly if:
  • renal impaired
  • elderly
  • neonates
  • Avoid in myasthenia gravis - reduces neurotransmission
47
Q

What are the interactions of gentamicin?

A
  • Ototoxicity - increased in combo with vancomycin and loop diuretics
  • Nephrotoxicity - increased in combo with nephrotoxic drugs
48
Q

How is gentamicin administered?

A

IV - dose dependent on patient weight and renal function

49
Q

Name 2 macrolides

A

ErythromYcin, clarithromYcin

50
Q

what is the mechanism by which clarithromycin/erythromycin (macrolides) exert their action?

A

Inhibit bacterial protein synthesis - block 50S of ribosome, preventing translocation

Broad spectrum against gram-/+ bacteria - especially H Infu

51
Q

What are the indications for erythromycin/clarithromycin? (macrolides)

A

Alternative to penicillin allergy

  • Respiratory Infection
  • soft tissue/skin infection (alternative to patient with penicillin allergy)
  • Severe pneumonia by atypical organism (+ penicillin)
  • Eradication Tx for H pylori (+ PPI & metronidazole/amoxicillin)
52
Q

What are the CIs for macrolides (erythromycin/clarithromycin?

A
  • Hepatic or renal impairment
  • Hypersensitivity
  • Existing arrhythmias - prolongs QT interval
53
Q

What are the SEs of macrolides (clarithromycin/erythromycin?)

A
  • GI upset
  • Hypersensitivity
  • Ototoxicity (in high doses)
  • Hepatic abnormalities (cholestatic jaundice)
  • Prolong QT interval
  • ABx associated colitis (C Diff)
54
Q

What are the potential drug interactions of macrolides (erythromycin/clarithromycin)

A
  • PY450 inhibitors - increases drug concentration/toxicity of drugs broken down by PY450)
  • Prolong QT interval - caution in other drugs that prolong QT interval (e.g. SSRIs, amiodarone, antipsychotics)
55
Q

Name 3 quinolones

A

Ciprofloxacin, mexofloxacin, levofloxacin

56
Q

What is the mechanism by which quinolones work?

A

Inhibit DNA synthesis

Active against gram- bacteria (newer ones e.g. levoflox, mexoflox - increased activity to gram+)

57
Q

What is the main problem with quinolones?

A

Bacteria gain rapid resistance against quinolones (therefore, reserved 2nd to 3rd line for most indications)

Associated with C Diff

58
Q

What are the indications for quinolones?

A

2nd - 3rd line for most interactions - resistance/C Diff association

  1. UTI - particularly men (2 weeks, 4 weeks if prostatis)
  2. Severe GI infection e.g. cympobacter, shigella
  3. Atypical pneumonia
  4. Ciprofloxacin - only oral ABx with activity against pseudo auerginosa
59
Q

What are the CI of quinolones?

A
  • People who are still growing (increased risk of arthropathy)
  • People at risk of seizures (lowers seizure threshold)
  • People with risk factors to increases QT interval (e.g. CV disease, arrythmias)
60
Q

What are the SEs of quinolones?

A
  • GI upset/hypersensitivity
  • Reduces seizure threshold
  • Prolongs QT interval
  • Inflammation and muscle tendon rupture
  • Associated with C Diff colitis
61
Q

What are the interactions of quinolones?

A
  • CYP450 inhibitor - increases concentration and toxicity of drugs broken down by CYP450
  • Prolong QT interval - avoid combination with other QT interval prolonging drugs e.g. SSRIs, antipsyhotics, tricyclic antidepressants
  • Do not take in combo with drugs/food containing divalent cations - binds to them and reduces absorption into gut
62
Q

Name one anaerobic antimicrobrial

A

Metronidazole

63
Q

What is the mechanism by which metronidazole works?

A

Only for anaerobic bacteria or protozoa infections (aerobic bacteria cannot reduce metronidazole)
- Enters bacterium/protozoa by passive diffusion > reduced > nitroso free radical > causes DNA degeneration and cell death

64
Q

What are the indications for metronidazole?

A
  1. ABx associated colitis (C Diff)
  2. Oral infections or aspiration pneumonia caused by gram- infections of mouth
  3. Surgical or gynaecological infections caused by gram- anaerobes of colon
    4 Protozoal infections
65
Q

What are the CI for metronidazole?

A
  • Metabolised by CYP450 - inhibitors/inducers/reduce with hepatic impairment
  • DO NOT DRINK WITH ALCOHOL - inhibits alcetyaldehyde dehydrogenase - breaks down alcohol metabolite acetyladehyde (causes hangover)
66
Q

What are the SEs of metronidazole?

A
  • Hypersensitivity
  • GI upset
  • CNS toxicity with high dose/prolonged causes - peripheral/optic neuropathy, seizures etc
67
Q

What are the interactions of metronidazole

A
  • CYP450 inhibitor

- Metabolised by CYP450 too

68
Q

Name one glycopeptide

A

Vancomycin

69
Q

What is the mechanism by which vancomycin/glycopeptide exerts its action?

A

Inhibits synthesis and crosslinking of peptidoglycans, preventing growth and synthesis of bacterial cell walls

Effective specifically against gram + bacteria and anaerobes (not gram- which have a different lipoopolypeptide wall structure)

70
Q

What are the indications for vancomycin/glycopeptide?

A
  1. Gram+ aerobic infections where infection is SEVERE or where penecillin cannot be used e.g. MRSA
  2. 2nd line for C Diff (where metronidazole is CI/not tolerated)
71
Q

What are the CIs for +vancomycin/glycopeptide?

A

Low theurapetuic index

Dose reduction in elderly/renal impairment (increased risk of side effects)

72
Q

What are the SEs of vancomycin/glycopeptides?

A
  • Thrombophlebitis at infusion site
  • Hypersensitivity reaction - if infusion too quick, red man syndrome - generalised erythema with hypotension and bronchospasm (not allergic reaction but caused by degranulation of eosinophils)
  • Ototoxicity
  • Nephrotoxicity
  • Blood disorders (e.g. neutropenia, thrombocytopenia)
73
Q

What are the potential interactions of glycopeptides/vancomycin?

A
  • Higher risk of ototoxicty/nephrotoxicity if given in combo with aminoglycosides, loop diuretics or ciclosporin
74
Q

How is vancomycin administered?

A

Oral - C Diff

IV - systemic infections

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