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Yr3 Pharmacology > Antibiotics > Flashcards

Antibiotics Flashcards

(61 cards)

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1
Q

Name a penecillin

A

Amoxycillin

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2
Q

How do penecillins work?

A

Inhibit enzymes which cross link peptidoglycan cell walls

Water gets in, cell lysis, death

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3
Q

How does penecillin resistance come about?

A

Beta-lactam in penecillin produces its desirable effects

Bacteria produce beta-lactamases

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4
Q

Give some indications of penecillin:

A

Streptococcal infection eg tonsilitis, pneumonia, endocarditis, skin infection
Clostridial infection eg tetanus
Meningococcal infection eg meningitis

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5
Q

When is penecillin contraindicated?

A

Allergy!
Usually safe otherwise.
Renal impairment: dose reduction

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6
Q

Name some common and not so common reactions to penecillin

A

skin rash 7-10 days after
IgE mediated anaphylaxis!
CNS toxicity in higher doses

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7
Q

What kind of antibiotic is cephradine and how does it work?1

A

Cephalosporin

Also has beta lactam ring that breaks up peptidoglycan cell wall

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8
Q

When would cephradine be used?

A

2nd line for UTI and respiratory tract infections

IV for severe/complex/resistant infections. Its a broad spectrum so its a good place to start.

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9
Q

When should cephradine be used in caution:

A

Penecillin allergy: similar drug

Those at risk of C.diff

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10
Q

Descibe an indirect interaction of caphradine

A

Kills normal gut fora which synthesises vikamin k, thus enhancing the anticoagulant effect of warfarin

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11
Q

Describe cephradines undesirable effects

A

GI upset common

Kills off normal gut flora, allowing c.diff to colonise

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12
Q

How does trimethoprim work?

A

Inhibits bacterial folate synthesis (bacteria can’t use external folate)

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13
Q

What is the spectrum and levels of resistance to trimethoprim?

A

Broad spectrum

Lots of resistance

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14
Q

When is trimethoprim commonly used?

A

uncomplicated UTI, 3 days

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15
Q

When is trimethoprim contraindicated?

A

1st trimester pregnancy
Folate deficiency
Caution in renal deficiency
Neonates, ill, HIV more suseptible to adverse effects

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16
Q

When would trimethoprim predispose to hyperkalaemia?

A

Potassium elevating drugs eg Aldosterone antagonists, diuretics, ACE inhibitors, ARB’s

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17
Q

Name of other side effects of trimethoprim than hyperkalaemia

A

GI upset and skin reactions in 3-7%
Can impair haematopoiesis causing blood disorders eg megaloblastic anaemia
Can enhance anticoagulant effect of warfarin by killing normal gut bacteria which may synthesis vitamin K

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18
Q

Why does the way trimethoprim is eliminated affect what it is used for?

A

Eliminated unchanged in urine -> UTIs!

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19
Q

How does nitrofurantioin work?

A

Metabolised by bacterial cells into nitrofuran reductase, which damages the bacterial DNA and kills the cell

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20
Q

What is nitrofuantoin commonly indicated for?

A

uncomplicated UTI

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21
Q

When is nitrofurantoin contraindicated?

A

Pregnant women towards end of term and babies in first 3 months of life
renal impairment

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22
Q

What are some side effects of nitrofurnatoin?

A

GI upset
hypersensitivity rare
turns urine dark
Haemolytic anaemia in neonates

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23
Q

What kind of spectrum do tetracyclines have?

A

Broad!

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24
Q

How do tetracyclines work?

A

Inhibit bacterial synthesis, bind to 30s subunit in bacteria. Protein chains cant form

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25
When are tetracyclines indicated??
Acne vulgaris LRTIs (infective exacerbations of COPD, pneumonia) Chlamidial infections including PID
26
What big groups of people are tetracyclines contraindicated in?
Pregnant, breastfeeding, children less that 12 (bind to teeth and bones during development) Renal impairment, can raise plasma urea
27
What kind of ion do tetracyclines bind to, and what does this mean in practice?
Divalent cations | Don't give within 2 hours of calcium, iron, antacids, as they won't be absorbed!
28
Name some common and not so common side effects of tetracyclines
Nausea, vomiting, diarrhoea | Hypersensitivity in 1% (No cross-reactivity to penecillins of beta lactams)
29
What kind of antibiotic is gentamicin?
Aminoglycoside
30
How does gentamicin work?
Binds irreversebly to 30s subunit of ribbosomes | Bacteriacidal!
31
What kind of bacteria does gentamicin not have an effect on?
Streptococci and anaerobes | Because it enters via the oxygen transport system, which these two dont have.
32
When is gentamycin indicated?
Gram negative aerobic bacterial infections, staphylococci, mycobacteria Sepsis pyelonephritis and complex UTI Biliary / intrabdominal sepsis Endocarditis Combine with penecillin / metronidazole when infection unknown
33
What kind of toxicity can gentamicin cause? (same as vancomycin) When are these toxiticies more likely to occur?
Nephrotoxicity and ototoxicity Accumilate in renal tubule and hair cells signalling apoptosis Nephro: when given with ciclosporin, cephalosporins, vancomycin Oto: loop diuretics or vancomycin
34
Name an example of a glycopeptide antibiotic
Vancomycin
35
What kinds of bacteria does vancomycin target?
Gram positive and anaerobes only
36
How dies vancomycin work?
Inhibits cross linking of peptidoglycan cell walls
37
Give 3 situations where vancomycin would be used
Severe gram positive infection eg endocarditis Where penecillin is contraindicated (allergy/resistance) Antibiotic associated collitis eg C.diff (usually 2nd line to metronidazole)
38
When is vancomycin more likely to cause nephro or ototoxicity?
When prescribed with loop diuretics, aminoglycosides (gentamycin) or ciclosporin
39
Name some side effects of vancomycin
``` Thrombophlebitis at injection site Nephrotoxicity and ototoxicity "Red man syndrome"-due to mast cell degranulation True allergy (IgE) Neutoropenia, thrombocytopenia ```
40
Name 2 macrolides
Erythromycin, Clarithromycin
41
How does erthromycin & clarythromycin work?
Binds to 50s subunit inhibiting protein synthesis | Bacteriostatic!
42
When would clarythromycin be used?
Respiratory, skin or soft tissue infections where penecillin contraindicated severe pneumonia with penecillins H.pylori in peptic ulcers with PPI and amoxycillin / metronidazole
43
What are some common contraindications to etythromycin use?
``` Macrolide sensitivity (but are useful in penecillin allergy) Severe hepatic or renal impairment ```
44
What do macrolides do to liver enzymes?
Clarithromycin and erythromycin are cytochrime p450 inhibitors!!! So increase warfarin and statins concentrations
45
Apart for cytochrome p450 drugs, what other drugs should erythromycin and clarythromycin be used in caution with?
Drugs that prolong QT interval eg amioderone, antipsychotics, quinine, quinolone, SSRIs
46
Name some common erythromycin side effects
Nausea, vom, diarrhoea, abdo pain (irritants) allergy ABx associated collitis eg C.diff Liver abnormalities eg Cholecystic jaundice Prolong QT interval Ototoxicity
47
Name a quinolone
Ciprofloxacin
48
How does ciprofloxacin work?
Inhibits DNA synthesis, especially gram negative
49
Name a drawback of quinolones
Bacteria quickly become resistant
50
When is ciprofloxacin indicated?
``` UTI severe GI infection eg shigella Pseudomonas aeraginosa LRTI Usually 2nd or 3rd line due to resistance ```
51
When should ciprofloxacin be used in caution?
Those at risk of seizures Those still growing Those at risk of QT elongation (electrolyte distrubance, cardiac arrhythmias)
52
Name some ciprofloxacin interactions
Drugs with divalent cations (calcium, antacids, iron)- reduce efficacy as not absorbed NSIADs- increase risk of seizures Other drugs that prolong QT interval
53
What does Ciprofloxacin do to Cytochrome p450 enzyme?
Inhibits it! Increases risk of drugs metabolised by it, especially theophylline
54
NAme some side effects of ciprofloxacin
``` Usually fine GI upset Hypersensitivity reactions Neuro defects Inflammation and rupture of tendons ```
55
What kind of bacteria does metronidazole go after?
Anaerobics! (aerobes dont reduce to free radical)
56
Which antibiotic is it essential not to drink alcohol while taking, and what happens?
Metronidazole, Disulphram like reaction (really sick) | Inhibits the enzyme which clears acetaldehide from body
57
How does metronidazole work?
Enters via passive diffusion Reduction of it causes free radical formation free radical binds to DNA, causing cell death.
58
When is mnetronidazole indicated?
``` Anaerobe infection eg C.diff Oral infections Aspiration pneumonia surgical and gynae infections Protozoal infections ```
59
What metabolises metronidazole?
cytochrome p450! Reducing metabolism of phenytoin and warfarin.
60
Why would the efficacy of cmetronidazole be reduced in someone taking riframpicin or phenytoin?
They are cytochrome p450 inducers, so get rid of metronidazole quicker.
61
Name some short term and long term side effects of metronidazole use
Short: GI upset, hypersensitivity Long: peripheral and optic neuropathy, seizures, encephalopathy

Yr3 Pharmacology (6 decks)

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