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Principles of Pharmacology > Antibiotics 2 > Flashcards

Antibiotics 2 Flashcards

1
Q

what does penicillin inhibit?

A

PBP

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2
Q

what is the chemical structure of a NAM subunit?

A

peptide side chains with 1 proximal L-alanine and 2 distal D-alanines

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3
Q

what does PBP do?

A

binds peptide side chains to form a cross link with the removal of 1 D-alanine

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4
Q

how does penicillin inhibit PBP?

A

enters the active site of PBP and reacts with the serine group which is important for activity

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5
Q

how does penicillin permanently block the active site of PBP?

A

the beta lactam ring of the penicillin is opened and it remains covalently linked to PBP

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6
Q

what bacteria does penicillin treat?

A

strep and staph, Neisseria, anaerobes, spirochetes

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7
Q

what are the pharmacokinetics of penicillin G?

A

acid labile, widely distributed, rapid renal excretion

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8
Q

how are some bacteria resistant to penicillin?

A

does not pass gram negative cell envelope very well and degraded by beta lactase enzymes

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9
Q

what are beta lactamase enzymes?

A

produced by bacteria and provide resistance to beta lactam antibiotics

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10
Q

how does beta lactam enzymes degrade beta lactam antibiotics?

A

break open the lactam ring via hydrolysis

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11
Q

what antibiotics are penicillinase resistant?

A

methicillin and oxacillin

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12
Q

what antibiotics have a broad spectrum?

A

amoxicillin and ampicillin

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13
Q

what antibiotics are antipseudomonas?

A

azlocillin and piperacillin

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14
Q

how is penicillin G administered?

A

requires injection

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15
Q

how is penicillin V administered?

A

can be taken orally

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16
Q

what are the natural penicillins?

A

pen V and pen G

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17
Q

what are the semisynthetic penicillins?

A

oxacillin and ampicillin

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18
Q

what are the clinical uses of penicillins?

A

pneumonia, meningitis, staph infections, syphilis, urinary tract infections

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19
Q

what are the adverse reactions to penicillins?

A

hypersensitivity, immediate anaphylaxis

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20
Q

what is augmentin?

A

combination of clavulanic acid and amoxycillin

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21
Q

what does clavulanic acid do?

A

acts as a beta lactam inhibitor

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22
Q

what is the mechanism fo augmentin?

A

acts as a competitive and reversible inhibitor of beta lactamase enzymes

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23
Q

what are the adverse reactions of cephalosporins?

A

hypersensitivity, thrombophlebitis and nephrotoxicity

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24
Q

how are cephalosporin variants produced?

A

modification of the side chain at position 7 and substituents on position 2 of the ring

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25
Q

what are the first generations of cephalosporins?

A

cephalosporin, cephalexin, cephradine

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26
Q

how are second generations of cephalosporins produced?

A

removal of methyl group

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27
Q

what are the second generation cephalosporins?

A

cefaclor and cefuroxime

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28
Q

how are third generation cephalosporins produced?

A

R1 and R2 groups changed ao that it is stable without refrigeration

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29
Q

what are the third generation cephalosporins?

A

cefotaxime and ceftriaxone

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30
Q

what are the most active cephalosporins against E.coli?

A

third generation

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31
Q

what cephalosporins have increased activity against pseudomonas aeruginosa?

A

third generation

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32
Q

what does third generation cephalosporins have decreased activity against?

A

gram-positive staphylococci

33
Q

what are the fourth generation cephalosporins?

A

cefepime and cefipriome

34
Q

how is a fourth generation cephalosporin created?

A

quaternary N-methyl pyrrolidine (NMP) at R1

35
Q

what is different about fourth generation cephalosporins?

A

improved resistance to beta lactamase and penetration of outer membrane of gram negative bacteria, extended spectrum

36
Q

what causes fourth generation cephalosporins to have minimal beta lactamase activity?

A

rapid periplasmic penetration and high PBP access

37
Q

what drug resistant bacteria is fourth gen cephalosporins effective against?

A

enterobacter and klebsiella

38
Q

what does isoniazid do?

A

inhibits cell wall synthesis due to no mycelia acid synthesis

39
Q

what is mycolic acid?

A

alpha-alkyl-beta-hydroxy long chain fatty acids

40
Q

how can resistance to isoniazid occur?

A

mycobacterial enzyme called peroxidase so depletion of peroxidase causes resistance

41
Q

how are neuropathic side effects of isoniazid ameliorated?

A

by co-administration of B6

42
Q

how does isoniazid lead to blocked fatty acid synthesis?

A

activated by KatG which catalyses the formation of INH-NAD complex, which then binds tightly to enoyl-aceyl carrier protein reductase which becomes inactive so no fatty acid synthesis

43
Q

how does blocked fatty acid synthesis lead to a damaged cell wall?

A

no mycolic acid synthesis

44
Q

what is rifampicin used to treat?

A

mycobacterium infections including tuberculosis and leprosy

45
Q

how does rifampicin inhibit RNA synthesis?

A

inhibits the bacterial dependant RNA polymerase

46
Q

what 3 drugs cause inhibition of protein synthesis?

A

chloramphenicol, tetracycline and streptomycin

47
Q

how does chloramphenicol work?

A

binds to the 50s subunit and inhibits formation of peptide bond

48
Q

how does tetracycline work?

A

interfere with attachment of tRNA to the mRNA-ribosome complex

49
Q

how does streptomycin work?

A

changes shape of the 30s subunit, causing the mRNA to be read incorrectly

50
Q

how are drugs that inhibit protein synthesis achieve selective toxicity?

A

due to translational events differing in eukaryotes and prokaryotes

51
Q

how large are eukaryotic and prokaryotic ribosomes?

A

eukaryotic = 80s and prokaryotic = 70s

52
Q

what antibiotics act on 50s subunits?

A

chloramphenicol, lincosamides, erythromycin and fusidic acid

53
Q

what are the 2 subunits of a prokaryotic ribosome?

A

50s and 30s

54
Q

what antibiotics act on the 30s subunit?

A

ahminoglycosides and tetracyclines

55
Q

what is the target for ahminoglycosides?

A

fmet binding and initiation complex

56
Q

what is an example of an amino glycoside?

A

streptomycin

57
Q

what is the target of tetracycline?

A

binding of tRNA to the available aminoacyl site on the 50s subunit

58
Q

what is the target for chloramphenicol and lincosamide?

A

the formation of a peptide bond

59
Q

what is the target for erythromycin?

A

translocation of peptidyl tRNA so removal of tRNA molecule prevented

60
Q

why might erythromycin be prescribed?

A

when someone is allergic to penicillin

61
Q

what does sulfamindes and trimethoprim do?

A

prevents formation of pyrimidine and purine

62
Q

what drugs are inhibitors of DNA replication? how?

A

quinolone as prevent action of DNA gyrase

63
Q

what drugs are inhibitors of RNA polymerase? how?

A

rifampicin as prevents RNA synthesis

64
Q

what are the 4 types of antiviral inhibitors?

A

protease inhibitors, entry inhibitors, reverse transcriptase inhibitors and non-nucleotide reverse transcriptase inhibitors

65
Q

what type of inhibitor is acyclovir?

A

nucleoside reverse transcriptase inhibitors

66
Q

how is acyclovir prodrug action increased?

A

after metabolisation, acyclovir-GTP has 100x higher affinity for viral polymerase

67
Q

how does acyclovir prevent viral replication?

A

incorporation into viral DNA causes premature chain termination

68
Q

what is target site alteration?

A

the target site is altered by reducing the affinity for the antibiotic without impairing cellular function

69
Q

what is the two types of target site alteration?

A

cell wall synthesis and protein synthesis

70
Q

how is target site altered in cell wall synthesis?

A

shift in amino acid sequence in PBP reduces the affinity for penicillin

71
Q

how is target site altered in protein synthesis?

A

shifts in amino acid sequence of ribosomal proteins reduces the affinity for erythromycin and tetracycline

72
Q

how is the access to target site modified to gain antibiotic resistance?

A

ability of antibiotic to enter bacterial cell and gain access to target site is impaired

73
Q

what are the mechanisms of antibiotic resistance?

A

target site modification, access to target site modified, inactivation of antibiotic and efflux

74
Q

how does the cell wall lead to resistance in terms of access to target site being modified?

A

alterations of the composition of bacterial membrane can reduce permeability for antibiotic

75
Q

what is inactivation of antibiotic?

A

antibiotics is inactivated by enzymes produced by bacteria

76
Q

how is cell wall synthesis involved in inactivation of antibiotic?

A

beta lactamase inactivates penicillin by catalysing lactam ring cleavage

77
Q

how is protein synthesis involved in inactivating an antibiotic?

A

amino glycoside modifying enzymes and chloramphenicol transferases prevent disruption of protein synthesis by modifying the structure of the antibiotic

78
Q

what is efflux?

A

the antibiotic enters the bacteria but rapid expulsion lowers the cytoplasmic concentration

Principles of Pharmacology (12 decks)

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