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Yr3 Pharmacology > Antibiotics > Flashcards

Antibiotics Flashcards

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
Q

When are tetracyclines indicated??

A

Acne vulgaris
LRTIs (infective exacerbations of COPD, pneumonia)
Chlamidial infections including PID

26
Q

What big groups of people are tetracyclines contraindicated in?

A

Pregnant, breastfeeding, children less that 12
(bind to teeth and bones during development)
Renal impairment, can raise plasma urea

27
Q

What kind of ion do tetracyclines bind to, and what does this mean in practice?

A

Divalent cations

Don’t give within 2 hours of calcium, iron, antacids, as they won’t be absorbed!

28
Q

Name some common and not so common side effects of tetracyclines

A

Nausea, vomiting, diarrhoea

Hypersensitivity in 1% (No cross-reactivity to penecillins of beta lactams)

29
Q

What kind of antibiotic is gentamicin?

A

Aminoglycoside

30
Q

How does gentamicin work?

A

Binds irreversebly to 30s subunit of ribbosomes

Bacteriacidal!

31
Q

What kind of bacteria does gentamicin not have an effect on?

A

Streptococci and anaerobes

Because it enters via the oxygen transport system, which these two dont have.

32
Q

When is gentamycin indicated?

A

Gram negative aerobic bacterial infections, staphylococci, mycobacteria
Sepsis
pyelonephritis and complex UTI
Biliary / intrabdominal sepsis
Endocarditis
Combine with penecillin / metronidazole when infection unknown

33
Q

What kind of toxicity can gentamicin cause? (same as vancomycin) When are these toxiticies more likely to occur?

A

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
Q

Name an example of a glycopeptide antibiotic

A

Vancomycin

35
Q

What kinds of bacteria does vancomycin target?

A

Gram positive and anaerobes only

36
Q

How dies vancomycin work?

A

Inhibits cross linking of peptidoglycan cell walls

37
Q

Give 3 situations where vancomycin would be used

A

Severe gram positive infection eg endocarditis
Where penecillin is contraindicated (allergy/resistance)
Antibiotic associated collitis eg C.diff (usually 2nd line to metronidazole)

38
Q

When is vancomycin more likely to cause nephro or ototoxicity?

A

When prescribed with loop diuretics, aminoglycosides (gentamycin) or ciclosporin

39
Q

Name some side effects of vancomycin

A 
Thrombophlebitis at injection site
Nephrotoxicity and ototoxicity
"Red man syndrome"-due to mast cell degranulation
True allergy (IgE)
Neutoropenia, thrombocytopenia
40
Q

Name 2 macrolides

A

Erythromycin, Clarithromycin

41
Q

How does erthromycin & clarythromycin work?

A

Binds to 50s subunit inhibiting protein synthesis

Bacteriostatic!

42
Q

When would clarythromycin be used?

A

Respiratory, skin or soft tissue infections where penecillin contraindicated
severe pneumonia with penecillins
H.pylori in peptic ulcers with PPI and amoxycillin / metronidazole

43
Q

What are some common contraindications to etythromycin use?

A 
Macrolide sensitivity (but are useful in penecillin allergy)
Severe hepatic or renal impairment
44
Q

What do macrolides do to liver enzymes?

A

Clarithromycin and erythromycin are cytochrime p450 inhibitors!!! So increase warfarin and statins concentrations

45
Q

Apart for cytochrome p450 drugs, what other drugs should erythromycin and clarythromycin be used in caution with?

A

Drugs that prolong QT interval eg amioderone, antipsychotics, quinine, quinolone, SSRIs

46
Q

Name some common erythromycin side effects

A

Nausea, vom, diarrhoea, abdo pain (irritants)
allergy
ABx associated collitis eg C.diff
Liver abnormalities eg Cholecystic jaundice
Prolong QT interval
Ototoxicity

47
Q

Name a quinolone

A

Ciprofloxacin

48
Q

How does ciprofloxacin work?

A

Inhibits DNA synthesis, especially gram negative

49
Q

Name a drawback of quinolones

A

Bacteria quickly become resistant

50
Q

When is ciprofloxacin indicated?

A 
UTI
severe GI infection eg shigella
Pseudomonas aeraginosa
LRTI
Usually 2nd or 3rd line due to resistance
51
Q

When should ciprofloxacin be used in caution?

A

Those at risk of seizures
Those still growing
Those at risk of QT elongation (electrolyte distrubance, cardiac arrhythmias)

52
Q

Name some ciprofloxacin interactions

A

Drugs with divalent cations (calcium, antacids, iron)- reduce efficacy as not absorbed
NSIADs- increase risk of seizures
Other drugs that prolong QT interval

53
Q

What does Ciprofloxacin do to Cytochrome p450 enzyme?

A

Inhibits it! Increases risk of drugs metabolised by it, especially theophylline

54
Q

NAme some side effects of ciprofloxacin

A 
Usually fine
GI upset
Hypersensitivity reactions
Neuro defects
Inflammation and rupture of tendons
55
Q

What kind of bacteria does metronidazole go after?

A

Anaerobics! (aerobes dont reduce to free radical)

56
Q

Which antibiotic is it essential not to drink alcohol while taking, and what happens?

A

Metronidazole, Disulphram like reaction (really sick)

Inhibits the enzyme which clears acetaldehide from body

57
Q

How does metronidazole work?

A

Enters via passive diffusion
Reduction of it causes free radical formation
free radical binds to DNA, causing cell death.

58
Q

When is mnetronidazole indicated?

A 
Anaerobe infection eg C.diff
Oral infections 
Aspiration pneumonia
surgical and gynae infections
Protozoal infections
59
Q

What metabolises metronidazole?

A

cytochrome p450! Reducing metabolism of phenytoin and warfarin.

60
Q

Why would the efficacy of cmetronidazole be reduced in someone taking riframpicin or phenytoin?

A

They are cytochrome p450 inducers, so get rid of metronidazole quicker.

61
Q

Name some short term and long term side effects of metronidazole use

A

Short: GI upset, hypersensitivity
Long: peripheral and optic neuropathy, seizures, encephalopathy

Yr3 Pharmacology (6 decks)

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