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DAST 7 Exam 2 > Synthetic Antimicrobial Agents - 15Qs > Flashcards

Synthetic Antimicrobial Agents - 15Qs Flashcards

1
Q

List synthetic Antimicrobial agents

A

Sulfonamides
Sulfones
Quinolones

They are non-natural in origin

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2
Q

MOA of Sulfonamides

A

Bacteriostatic antimetabolite

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3
Q

What are Sulfonamides analogs of?

A

P-aminobenzenesulfonamide

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4
Q

What enzyme catalyses Dihydropteroate diphosphate to Dihydropteroic acid

A

Dihydropteroate synthase (inhibits the above conversion)

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5
Q

Are Sulfonamides used orally?

A

First safe and effective oral anti-infective agent

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6
Q

Name other MOA of Sulfonamides in other bacteria

A

Sulfonamides also block the biosynthesis of dihydrofolic acid by acting as a FALSE METABOLITE

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7
Q

Role of Dihydropteroate synthase here

A

The false metabolizes are converted by Dihydropteroate synthase to a more advanced intermediate which can’t continue down normal pathway

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8
Q

Which bacteria are intrinsically resistant to Sulfonamides

A

Bacteria capable of taking up pre-formed Folic acid (Vit B9)

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9
Q

Why are humans immune to the anti-metabolite effect of Sulfonamides

A

Humans do not have the necessary enzymes needed to biosynthesize Folic acid

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10
Q

What does the Sulfonamide moiety mimic?

A

Carboxyl group of PABA

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11
Q

What is the PKa of Carboxyl group of PABA

A

6.5

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12
Q

What’s the relationship btw the acidity of the NH group on the sulfonamide and it’s inhibition?

A

The more acidic the NH on Sulfonamides is, the better the inhibition and and the more water soluble the drug is at physiological PH.

For example, Sulfanilamide Pka = 10.4

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13
Q

What’s the role of resonance in stability of the Sulfonamides?

A

The ability of the NH group to undergo resonance leads to stability of the molecule.

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14
Q

List other factors that enhance stability in Sulfonamides.

A

Acidity is enhanced by substitution of a heterocyclic ring for ONE of the HYDROGENS of the sulfonamide moiety.

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15
Q

List primary uses of Sulfonamides (becuz of their broad spectrum)

A

A. Uncomplicated UTI cuzed by E. coli

B. Pneumocystis carinii infections in immune compromised pts e.g. AIDS and organ transplant pt

C. As 2nd or 3rd choice for most other susceptible bacteria

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16
Q

Are Sulfonamides orally active?

How are they excreted?

A

Yes.

They are excreted in active form in urine

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17
Q

How are Sulfonamides metabolized?

A

Partially deactivated in the LIVER by

A. N-4 acetylation (MAIN)

B. by glucoronidation

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18
Q

Are Sulfonamides protein bound?

A

Yes.

Intermediate (30- 70 %)

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19
Q

MOA of plasmid resistance (which is very common in Sulfonamides)

A

Altered Dihydropteroate synthase

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20
Q

What’s the main AE of Sulfonamides?

A

Allergy (rash, photosensitivity and drug fever. SJS can happen, but is rare)

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21
Q

What AE was common?

What advise would be given to pts to combat this?

A

Crystalurea, which led to Nephritis

Patients advised to drink lots of water

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22
Q

Are Sulfonamides cross allergen with penicillin

A

No

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23
Q

What enhances acidity?

A

Heterocyclic rings

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24
Q

Name specific-use sulfa drug.

What’s it used for?

A

Sulfasalazine

Prodrug for ulcerative colitis and crohns dx (anti-inflammatory)

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25
Q

What are the metabolizes of sulfasalazine?

Which is the active one?

A

Metabolized by gut flora to
Sulfapyridine and MAS

MAS- is the active one, but is a GUT irritant, so can’t be admin directly

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26
Q

What is the function of MAS

A

MAS is the active ingredient that treats both ulcerative colitis and crohn’s dx due to its anti-inflammatory activity

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27
Q

What’s the diff btw Sulfone and Sulfonamide?

A

Sulfone central sulfur atom is attached to 2 carbons

Sulfonamides central sulfur atom is attached to 1 carbon and 1 Nitrogen

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28
Q

What’s Sulfone used for?

A

Special utility in treating Hansen’s dx (leprosy) caused by Mycobacterium leprae.

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29
Q

How’s tx regime for leprosy

A

Prolonged tx, but doesn’t replace lost tissue

Sulfone is used in combo with Rifampicin

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30
Q

Role of Trimethoprim

A

Target similar pathway as sulfur drug, but they target diff enzymes, but final outcome is still prevention of folate therefore preventing DNA/RNA synthesis

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31
Q

What does trimethoprim inhibit

A

Dihydrofolate reductase

Inh Dihydrofolic acid from converting to Tetrahydofolic acid

32
Q

How does Trimethoprim differentiate btw human cells and bacteria?

A

Selective toxicity

DFHR in humans is 20,000-40,000 times less sensitive than bacterial enzyme

33
Q

How’s trimethoprim used?

It’s MOA?

A

PO

Bacteriostatic

34
Q

When is the Parenteral form used?

A

In AIDS pt

35
Q

Is trimethoprim synergistic with Sulfonamides

A

Yes.

36
Q

How’s the combo of trimethoprim/sulfonamide used?

A

1:5 ratio

37
Q

Can trimethoprim be used as an individual agent?

A

Yes.

It’s increasingly used as a single therapeutic agent

38
Q

Describe the spectrum of trimethoprim?

A

Intrinsically broad spectrum

39
Q

What are trimethoprim/sulfonamide used?

A

Primarily against UTI

Significant use against Shigelliosis, otitis media, traveller’s diarrhea, and bronchitis

40
Q

How does resistance dev in trimethoprim

A

Resistance dev fast via alteration in the structure of DHFR

Because of R-factor plasmid transfer

41
Q

List the most common SEs

A

Rash, nausea and vomiting

42
Q

Name rare SEs of trimethoprim

A

Blood dysuriasias and PMC due to superinfection by C. Diff

43
Q

Name the Quinolones

A

Nalidixic acid
Oxolinic acid
Cinnoxacin
Enoxacin

44
Q

Does resistance dev to Quinolones?

A

Yes.

Very quickly

45
Q

Uses of Quinolones

A

Primarily for UTI

46
Q

Quinolones wrt
A. Absorption
B. Protein binding
C. SEs

A

A. Well absorbed

B. high protein binding

C. GI upset, rashes, photosensitivity, visual disturbances, convulsion

47
Q

Fluoroquinolones.

What’s the effect of the addition of F to the quinolone structure?

A

F at C-6 Increases gram tve activity => broader spectrum

48
Q

What’s the effect of piperazine attached to C-7 of Fluoroquinolones

A

Increases anti-psuedomonas activity

49
Q

What decreases the potency of Fluoroquinolones

A

Antacid
Hematinics
Tonics
Diary products

50
Q

What’s the effect of methoxy added to C-8 of Fluoroquinolones
In 3rd gen?

A

Increases anti-gram positive effect

51
Q

MOA of Fluoroquinolones

A

Bactericidal

52
Q

How does Fluoroquinolones carry out it bactericidal action

A

Inh bacterial DNA GYRASE and Topoislmerase IV(but nor mammalian Topoislmerase II)

53
Q

How does resistance dev to Fluoroquinolones

A

Decreased uptake

Altered DNA gyrase or topoiosomerase

54
Q

List SE Of Ciprofloxacin (covers Fluoroquinolones in gen)

A 
Pro-convulsant
Occasional Hallucination
GIT (diarrhea, vomiting, abdominal pain, anorexia)
Insomnia
Visual disturbance
55
Q

Can epileptics use Ciprofloxacin?

A

Not recommended

It’s pro-convulsant esp I. Epileptics

56
Q

Counseling pt for insomnia using Fluoroquinolones

A

Pt to avoid caffeine, as this may potentiate insomnia

57
Q

Why is Ciprofloxacin not given b4 puberty or to women of child-bearing age?

A

Erosion of (wt-bearing) joints

58
Q

What’s the concern of people with cardiovascular issues about Fluoroquinolones?

A

Prolongation of QT interval which may lead to Arrythmias

59
Q

Effect on NSAIDS on Ciprofloxacin

A

NSAIDs may exacerbate the CNS and convulsive SEs

60
Q

Effect of the C-8 methoxy on Fluoroquinolones

A

They have lowered/ no liver metabolism

Have increased activity against topoiosomerase IV(becuz gram tve hv more topoiosomerase than gyrase)

61
Q

Is Ciprofloxacin broad-spectrum?

A

Yes.

And used for many infections including UTI

62
Q

Nitroimidazoles

Name the main agent here

A

Metronidazole

63
Q

Uses of Metronidazole

A

Amoebal vaginitis (main use)

Also used for
Trichomoniasis, Giardiasis and Gardnerella vaginitis

64
Q

What m.o. does metronidazole target?

A

Protozoa (not bacteria)

65
Q

What’s the MOA metronidazole?

A

Bactericidal

66
Q

How does metronidazole carry out its action?

A

By partial reduction of the NITRO group to poorly characterized product.

67
Q

What’s the effect of the poorly characterized pdts?

A

Bind with critical cysteine-containing enzyme, which leads to the death of m.o.

68
Q

List miscellaneous UTI drugs

A

Macrodantin/Nitrofurantoins
Phosphomycin
Methenamine/Hexamethylenetetramine

69
Q

What are Macrodantin/Nitrofurantoin used for?

A

UTI prophylaxis

70
Q

MOA of Macrodantin/Nitrofurantoin

A

Inh DNA/RNA fxns

Bactericidal

71
Q

What happens as a result of rapid absorption of Macrodantin/Nitrofurantoin?

A

Nausea and vomiting

72
Q

MOA of phosphomycin

A

BcteriCIDAL

Inh cell wall synthesis at an early phase

73
Q

Primary uses of Phosphomycin

A

E. coli

Enterobacter faecalis

74
Q

What happens to Methenamine/Hexamethylenetetramine in acid?

A

It depolarizes resulting in liberated formaldehyde

75
Q

What’s the effect of the liberated formaldehyde (from Methenamine/Hexamethylenetetramine)

A

Non-specific bactericide

76
Q

Whats Methenamine/Hexamethylenetetramine used for?

A

Recurrent UTI inf

DAST 7 Exam 2 (9 decks)

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