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MBChB3 > Antibiotics Used In Clinical Practice > Flashcards

Antibiotics Used In Clinical Practice Flashcards

1
Q

Describe the use of amoxicillin

A
  • used principally for streptococci for RTIs (good because streptococci is main cause of RTIs)
  • potentially against non-resistant coliforms and some anaerobes (but only if confirmed to be sensitive - likely to be resistant)
  • not for gram-negatives or S. aureus
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2
Q

What are beta-lactams and what are they used to treat?

A
  • naturally occurring antibiotics
  • best for serious and mild infection (very safe, effective and low cost)
  • usually always chosen if available
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3
Q

Describe the mechanism of action of beta lactams

A
  • all contain beta-lactam ring which resembles the structure of the PDG bacterial cell wall (target)
  • inhibits cross-linking of cell wall PDG
  • bacteriocidal - causes lysis
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4
Q

What are the adverse effects of beta lactam antibiotics?

A
  • usually well tolerated even in high doses
  • most common= GI toxicity (nausea and vomiting, diarrhoea, cholestasis (rare))
  • hypersensitivity (Type 1 - hives, anaphylaxis, Type 4 - mild to severe dermatological reaction)
  • infection (can occur with any antibiotics) - Eg. Oral candidiasis, C. Diff infection, resistance of bacteria
  • rare reactions eg. Seizure, haemolysis, leukopenia
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5
Q

What is the meaning of cross-reactivity in the context of penicillin allergy?

A
  • patients who are allergic to one type of penicillin will usually be allergic to other penicillins
  • but cross-reactivity with other antibiotic classes is less frequent (ie. Some patients will be able to take other beta-lactams)
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6
Q

What is flucloxacillin and what is it used to treat? Any side effects?

A
  • synthetic penicillin modified to overcome S. aureus beta-lactamase (side-chain modification)
  • gold standard treatment for soft tissue infection and S. aureus (ONLY MSSA)
  • can be used for strep infections but not as well tolerated as amoxicillin (more GI upset and renal/liver dysfunction)
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7
Q

What is co-amoxiclav and what is it used to treat? Side effects?

A
  • combination drug of amoxicillin and beta-lactamase inhibitor clavulanic acid
  • broadest spectrum of beta-lactam antibiotics (S. aureus, strep, some coliforms and anaerobes)
  • can be used for most infection but only used for empirical therapy if mild
  • cholestasis common side effect
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8
Q

What is ceftriaxone and what is it used to treat?

A
  • cephalosporin antibiotic
  • resistant to beta-lactamases (due to different affinity for PBPs)
  • broader spectrum for gram-negatives than co-amoxiclav (+ S. aureus, strep, coliforms)
  • used mainly for CNS infections eg. Bacterial meningitis
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9
Q

What is piperacillin/tazobactam and what is it used to treat?

A
  • tazobactam = beta-lactamase inhibitor
  • broad spectrum for gram-negatives (resistance common) - (+ S. aureus, strep, coliforms and anaerobes)
  • first line for neutropenic sepsis in immunocompromised patients
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10
Q

What is meropenem and what is its implications?

A
  • carbapenem antibiotic in beta-lactam class
  • ultrabroad-spectrum antibiotic - can be used against most common infection (except MRSA and some resistant gram-negatives)
  • resistance growing problem (ecological impact)
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11
Q

List the broad spectrum antibiotics in order of growing spectrum

A
  • amoxicillin
  • co-amoxiclav
  • ceftriaxone
  • piperacillin/tazobactam
  • meropenem
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12
Q

What is vancomycin and what is it used to treat?

A
  • glycopeptide antibiotic (very large and bulky structure makes it difficult to penetrate site of infection + slower breakdown of infection, flucloxacillin usually preferred)
  • ultrabroad spectrum gram-positive antibiotic and CAN be used for MRSA! (+ MSSA S. aureus, strep)
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13
Q

Describe the possible toxicity problems associated with vancomycin

A
  • nephrotoxicity (more likely with prolonged, higher doses)
  • red-man syndrome (swelling and redness, anaphylactoid reaction - rare if infusion rate is kept slow)
  • ototoxicity (rare)
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14
Q

What is gentamicin used to treat and features of its spectrum?

A
  • mainly for gram-negative pathogens incl the difficult to treat ones (common in management of UTI/abdominal infections)
    • S. aureus, coliforms
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15
Q

Describe the mechanism of action of gentamicin

A
  • reversible binding to 30s ribosome (prevents protein production in ribosome and has post-antibiotic effect where growth is continued to be inhibited even after therapy has finished)
  • rapid killing early in dosing interval
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16
Q

What are the toxicity effects of aminoglycosides such as gentamicin?

A
  • nephrotoxicity
  • ototoxicity (hearing loss, imbalance and oscillopsia)
  • neuromuscular blockade (significant in patients with MSK problems eg. Myasthenia gravis)
17
Q

Describe the dosage strategy used for aminoglycoside antibiotics such as gentamicin

A
  • once-daily dosing
  • high dose given initially (rapid killing)
  • long dosing interval (24-48hrs) to minimise toxicity
  • trough level is monitored to ensure no accumulation
  • short duration (3 days)
18
Q

What are the main mechanisms of action of antibiotics?

A

Targets:
- protein biosynthesis of ribosome (eg. Macrolides, aminoglycosides, tetracyclines)
- DNA and RNA replication (eg. Rifampicin, quinolones eg. ciprofloxacin)
- folate metabolism = impaired nucleotide synthesis = impaired DNA replication (eg. Trimethoprim)

19
Q

What are macrolides used for and its main advantage?

A
  • good against gram-positives and respiratory gram-negatives, good for atypicals as well (eg. Legionella, mycoplasma and chlamydia)
    • S. aureus, strep
  • excellent oral absorption even in severe infection
20
Q

What are the adverse effects and drug interactions to be aware of in macrolides?

A
  • side effects = diarrhoea, vomitng, QT prolongation, hearing loss (in long-term)
  • drug interactions = simvastatin (can cause dangerous build up), atorvastatin, warfarin
  • ^ stop temporarily
21
Q

What is clindamycin used for?

A
  • principal action is against gram-positives
    • S. aureus, strep, anaerobes
  • no action against aerobic gram-negatives or atypicals
  • good as additional management for gram-positive toxin mediated disease (eg. Toxic shock syndrome) = stops exotoxin production
  • good at disrupting colonic flora (severe diarrhoea treatment)
22
Q

What is the main caution for clindamycin use?

A

C. Difficile infection

23
Q

Describe how C. Diff can be acquired through antibiotic use

A
  • antibiotic use alters the flora resulting in a loss of diversity and the production of an good environment for other bacteria to grow
  • C. Diff colonises the colon and forms spores which are hard to eradicate
  • has developed resistance to common antibiotic classes
24
Q

What are the 4 main antibiotics which are risky for C. Diff infection?

A
  • clindamycin
  • co-amoxiclav
  • cephalosporins
  • ciprofloxacin
25
Q

What are tetracyclines used for and its cautions?

A
  • S. aureus, strep, atypicals
  • used mainly for RTIs and non-severe skin and soft tissue infections
  • relatively non-toxic
  • DO NOT USE in children/pregnant women (bone abnormalities + tooth discolouration)
26
Q

Describe the toxicity effects of quinolones

A
  • GI toxicity
  • QT prolongation
  • tendonitis (rupture)
27
Q

What is ciprofloxacin used for?

A
  • principally used for gram-negative pathogens
  • useful in UTI/intra-abdominal infections
    • coliforms and atypicals eg. Psedomonas
28
Q

What is levofloxacin used for?

A
  • principally LRTI/pneumonia
  • increased activity against gram-positive than gram-negative
  • S. aureus (incl MRSA), strep, coliforms, atypicals
29
Q

What is rifampicin used for?

A
  • TB
  • in addition to another antibiotic in serous gram-positive infection
  • ALWAYS combination therapy
30
Q

Describe the interaction problems associated with rifampicin

A
  • important to check if patient is on drugs which undergo hepatic metabolism
  • rifampicin is potent CYP450 enzyme inducer
31
Q

What is trimethoprim used for?

A
  • good for gram-positive and gram-negative bacteria
  • resistance is major problem
  • principally used in uncomplicated UTI
32
Q

Describe the toxicity effects of trimethoprim

A
  • elevation of serum creatinine (due to action on proximal tubules)
  • elevation of serum K+ (problem if renal impairment)
  • rash + GI disturbance
  • if used with sulphamethoxazole (co-trimoxazole) = bone marrow suppression, Stevens Johnson syndrome (rash)
33
Q

What is the mechanism of action of metronidazole and its use?

A
  • works by passive diffusion and production of free radicals
  • useful against anaerobic bacteria
  • usually used in combination for intra-abdominal infections esp abscesses
34
Q

What are the adverse effects of metronidazole?

A
  • unpleasant reaction with alcohol (sickness)
  • peripheral neuropathy with long term use

MBChB3 (100 decks)

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