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Year 3 Drug Formulary > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

How do penicillins and cephalosporins work?

A

Inhibits bacterial cell wall synthesis by preventing cross linking between peptidoglycan chains

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2
Q

What is amoxicillin used for?

A

Has activity against gram +ve (strep, staph) and gram -ve (H.influenzae, E.coli) bacteria. Commonly susceptible infections include UTIs, otitis media, sinusitis, uncomplicated CAP, salmonellosis, oral infections. Also used in combination in H.pylori eradication

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3
Q

Which strains of bacteria would rule out amoxicillin (and other Beta lactam) use?

A

Bacteria that produce beta lactamase enzymes.

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4
Q

What are the cephalosporin generation drugs?

A

1st gen - cefradine
2nd gen - cefuroxime
3rd gen - cefotaxime
Less activity against gram +ve bacteria the higher the generation. 2nd gen less susceptible to beta lactamase inactivation. 3rd gen greater activity against certain gram -ve bacteria

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5
Q

What is a common side effect to be wary of when using the cephalosporins?

A

Antibiotic-associated colitis

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6
Q

Interaction of cephalosporins with aminoglycosides?

A

Increased risk of nephrotoxicity

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7
Q

How do antifolate antibiotics Trimethoprim and Sulfonamides work?

A

Inhibit folate synthesis. Trimethoprim inhibits dihydrofolate reductase, sulfonamides inhibit diaminopteroate synthetase. Combined as co-trimoxazole

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8
Q

What is trimethoprim commonly used to treat?

A

UTIs. Can also be used in resp-tract infections, acne resistant to other Abx, prostatits, shigellosis, invasive salmonella

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9
Q

What is the interaction of trimethoprim and sulfonamide use with methotrexate?

A

Increased risk of severe bone marrow depression

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10
Q

Why is trimethoprim and sulfonamides use becoming a problem?

A

Resistance is common

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11
Q

How does nitrofurantoin work?

A

Broad spec ABx that inhibits DNA, RNA, protein and cell wall synthesis

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12
Q

What is nitrofurantoin used for?

A

UTIs. Effective against E. Coli, Enterobacter cystitis, Enterococcus, Klebsiella, and Staphylococcus aureus

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13
Q

Contraindications to nitrofurantoin use?

A

Acute porphyrias, G6PD deficiency, infants < 3 months old

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14
Q

Which strain of bacteria is completely resistant to nitrofurantoin?

A

All pseudomonas strains

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15
Q

What type of antibiotic is doxyxycline?

A

Tetracyclines

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16
Q

How does doxycycline work?

A

Protein synthesis inhibitor, inhibits RNA translation

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17
Q

What is doxycycline used for?

A

Susceptible infections caused by chlamydia, rickettsia, mycoplasma

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18
Q

Why should doxycycline use be cautioned with myasthenia gravis and SLE?

A

Can increase muscle weakness in myasthenia gravis and exacerbate SLE

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19
Q

Why should doxycycline and other tetracyclines not be given to children under 12 or pregnant women?

A

Doxycycline deposits on teeth and bone, causing staining and dental hypoplasia

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20
Q

Examples of aminoglycosides?

A

Gentamicin, streptomycin

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21
Q

How does gentamycin work?

A

Protein synthesis inhibitor, binds to 30S subunit

22
Q

Indications for aminoglycoside use?

A

Serious aerobic gram -ve infections and staph. Gentamycin against P. aeroginosa, streptomycin against M. tuberculosis

23
Q

Why is aminoglycoside use contraindicated in those with myasthenia gravis?

A

NMJ transmission can be impaired

24
Q

Side effects to be wary of with aminoglycosides?

A

Ototoxicity and nephrotoxicity

25
Q

Why is drug monitoring essential when on aminoglycosides?

A

Narrow therapeutic index, also not normally used for more than 10 days due to toxicity risk

26
Q

What is often used in combination with aminoglycosides in streptococcal endocarditis/other serious infections in blind therapy?

A

Beta lactams such as penicillin

27
Q

What syndrome can be caused in neonates if aminoglycosides have been used?

A

Grey baby syndrome

28
Q

What type of antibiotic is erythromycin?

A

Macrolide

29
Q

How does erythromycin work?

A

Protein synthesis inhibitor, inhibits protein elongation

30
Q

Why is clarithromycin given BD whilst erythromycin is given QDS?

A

Clarithromycin has greater activity and better tissue availability

31
Q

What is erythromycin used for?

A

Similar spectrum to penicillins so used as alternative in pen allergic patients. Gram +ve (and some gram -ve) infections

32
Q

Why is erythromycin enteric coated?

A

It is adversely affected by gastric acid

33
Q

Why are only short courses of macrolides given?

A

Resistance is quite rapid, >14 days use increases risk of hepatic damage

34
Q

Example of quinolone?

A

Ciprofloxacin

35
Q

How does ciprofloxacin work?

A

Inhibits DNA gyrase and topoisomerase IV which are involved in DNA remodelling. (Humans don’t have DNA gyrase)

36
Q

What is ciprofloxacin used for?

A

Broad spec. Particularly active against gram -ve bacteria (campylobacter, neisseria, pseudomonas)

37
Q

What type of weather should be avoided when on quinolones?

A

Excessive sunlight

38
Q

How does metranidazole work?

A

Broken down to toxic compounds within anaerobic microbes.

39
Q

What is metranidazole used for?

A

Anaerobic protozoal infections, H.pylori infection, rosacea, pseudomembranous colitis

40
Q

Why can’t alcohol be consumed when using metranidazole?

A

Disulfiram-like reaction can occur (flushing/abdo pain/hypotension)

41
Q

What type of antibiotic is vancomycin?

A

Glycopeptides

42
Q

How does vancomycin work?

A

Inhibits cell wall synthesis

43
Q

What is vancomycin used for?

A

Gram +ve infections both aerobic and anaerobic including MRSA. Treatment of endocarditis and C.diff

44
Q

Why should vancomycin not be given PO for systemic infections?

A

Poorly absorbed

45
Q

Side effects of vancomycin?

A

Ototoxic and nephrotoxic, blood disorders, N, chills, fever, flushing of upper body ‘red man’ syndrome

46
Q

Which antibiotics are safe to use in pregnancy?

A

Penicillins and cephalosporins

47
Q

Which antibiotics are NOT safe to use in pregnancy?

A

Chloramphenicol, tetracyclines, fluouroquinolones, co-trimoxazole

48
Q

Tazocin is a combination of which drugs?

A

Piperacillin and tazobactam

49
Q

Vancomycin only has activity against which type of organism?

A

Gram +ve bacteria

50
Q

Aztreonam only has activity against which type of organism?

A

Gram -ve bacteria

Year 3 Drug Formulary (10 decks)

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