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Pharmacology > Antibugs > Flashcards

Antibugs Flashcards

1
Q

Which antibiotics affect cell wall synthesis?

A

B lactams (penicillins, cephalosporins, carbapenems)
Glycopeptides (vanc, teic)

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2
Q

How do b lactams work

A

Rely on the integrity of the b lactam ring for bacteriocidal activity
Bind to and inhibit the enzyme that catalyzes the cross linking btw polymer chains in the cell wall, causing weakening followed by cell lysis

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3
Q

How do glycopeptides work

A

Bind the the peptidoglycan chains preventing formation of peptide x linking

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4
Q

WHich antibiotics inhibit protein synthesis

A

MAcrolides
TEtracyclines
aminoglycosides
Licosamides
Chloramphenicol

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5
Q

What is the difference btw bacterial and mammalian ribosomes

A

bacterial- 50s + 30s subunits
Mammalian have a 60s and 40s

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6
Q

How do macrolides (erythromycin) work

A

Bind to the 50s subunit inhibiting peptide chain translocation

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7
Q

How do tetracyclines work

A

Bind to the 30 s subunit and inhibit binding of aminoacyl-tRNA

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8
Q

How do aminoglycosides work?

A

Also bind to the 30s subunit and cause misreading of mRNA

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9
Q

Lincosamides MOA ?

A

eg clindomycin
Disrupt the function of the 50s subunit

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10
Q

How does chloramphenicol work?

A

Inhibits peptidyl transferase activity of the 50s subunit, stopping transpeptidation

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11
Q

Which abx inhibit nucleic acid synthesis?

A

Trimethoprim
Quinolones
metronidazole
Rifampacin

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12
Q

HOw does trimethoprim work?

A

Inhibits dihydrofolate reductase needed in purine/pyrimadine synthesis (bacteriostatic)

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13
Q

How do quinolones work?

A

Inhibit DNA gyrase, the enzyme that compresses DNA into coils

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14
Q

How does metronidazole work?

A

INhibits and damages dna synthesis (unclear exact MOA)

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15
Q

How does rifampacin work?

A

Prevents rna transcripton by inhibiting DNA dependent RNA polymerase

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16
Q

WHen is it important to use a bacteriocidal agent?

A

In the immunosuppressed

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17
Q

Bacteriostatic drugs?

A

MAcrolides
licosamides
chloramphenicol
tetracyclines
trimethoprim

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18
Q

Characteristics of penicillins?

A

Low toxicity, short half life, renal excretion unchanged
HYpersensitivity in 10%, anaphylaxis in 1
Side effects incl encephalopathy and didarrhoea
Tissue penetration good, but meninges need to be inflammed to cross the BBB

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19
Q

CHaracteristics of cephalosporins

A

Less susceptible to b lactamases
broader spec
Excreted unchanged in urine (bar cefotaxime which is 50% metabolsied in the liver)

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20
Q

What is different about ceftriaxone c.w. other cephalosporins

A

Highly protein bound (95%) with a long half life (6-12 hr) only given OD

21
Q

How are cephalosporins divided?

A

Three generations, increasingly more gram negative cover whilst positive cover is maintained

22
Q

Second generation cephalosporins examples and use

A

Cefuroxime
More stable b lactam ring used for prophylaxis in bowel surgery, lack anaerobic cover

23
Q

Third generation cephalosporins examples

A

cefotaxime, ceftriaxone, cepftazidime

24
Q

Carbapenem cover

A

broad- positive, negative, aerobic and anaerobicUS

25
Q

Uses of carbapenems

A

Neutropenic and multiresistant gram neg sepsis.

26
Q

What do carbapenems not work on

A

MRSA, E faecalis and some pseudomonas

27
Q

WHy is imipenem combined with cilastatin

A

Prevent renal metabolism and increase plasma conc.

28
Q

S/E of carbapenems

A

generally well tolerated but can cause convulsions. Excreted unchanged

29
Q

GLycopeptide cover

A

gram positive spectrum and used in MRSA + endocarditis.
GRam negative cover limited as large polar molecules cannot penetrate the outer lipd wall

30
Q

DIfference between teic and vanc?

A

TEic is more potent, longer duration of action, better tissue penetration and better tolerated. More resistance about

31
Q

CHaracteristics of glycopeptides

A

Toxicity common- nephro/oto/neutropenia. monitoring required.
ELimination unchanged in urine
Minimal absorption from gut
Can cause red man syndrome- IV vanc can lead to histamine release

32
Q

MAcrolide spectrum

A

SImilar to penicillin, mainly gram positive organisms
SPecific activity against mycoplasma and legionella

33
Q

What is good about azithromycin

A

increased gram negative cover with a v long half life (40-60 hrs)

34
Q

CHaracteristics of macrolides

A

Well tolerated
metabolised and excreted by the liver
potent inhibitors of the CYP450 enzymes

35
Q

Side effects of macrolides?

A

GI (erythromycin is a prokinetic), prolonged QT< thrombophlebitis

36
Q

Cover of aminoglycosides?

A

Mainly gram negative, including pseudomonas. First line for serious gram negative infections

37
Q

Pharmacokinetics of AMinoglycosides?

A

LArge, polar molecules needing active transport into the cell.
Renally excreted
IV required due to low lipid solubility

38
Q

Why do aminoglycocides work well with penicillins?

A

Penicillins break down the cell wall, giving aminoglycosides better cellular access

39
Q

S/E aminoglycosides

A

Toxic to kidneys and cn8 with narrow therapeutic range
Impair transmission at NMJ by decreasing prejunctional release and reducing post junctional sensitivity to Ach

40
Q

Quinolones uses?

A

Broad spec so often gastroenteritis or multiple resistant infetions
Tends towards covering gram neg, but some pos

41
Q

Difference between cipro and levofloxacin?

A

Levo has increased pneumococcal cover, useful for LRTI

42
Q

Characteristics of quinolones?

A

Good oral absorption
wide distribution with good cns penetration
excreted unchanges
low toxicity
INhibits cyp450

43
Q

S/E quinolones

A

nausea, vomiting, convulsions, prolonged qtc

44
Q

WHat is metronidazole good for?

A

Anaerobic bacteria- these predominate in abscesses so useful here

45
Q

Characteristics of metronidazole

A

Well tolerated
Distributes in csf, prostate and pleural fluid
Excreted unchanged in urine

46
Q

Rare side effects of metronidazole

A

rash
pancreatitis
peripheral neuropathy
Flushing and hypotension with alcohol

47
Q

Why are quinolones bad in epilepsy?

A

GABA antagonism

48
Q
A

Pharmacology (12 decks)

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