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Pharmacology -- Test #2 > Aminoglycoside Antibiotics > Flashcards

Aminoglycoside Antibiotics Flashcards

1
Q

Core structure of aminoglycoside antibiotics

A

1,3-diaminocyclitol

sually linked to one or more aminoglycoside rings

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2
Q

Three core structures of…

A

Streptidine
2-Doxystreptamine
Spectinamine

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3
Q

Seven clinically important aminoglycosides…

A 
Tobramycin
Kanamycin A
Amikacin A
Gentamycin C2
Neomycin B
Streptomycin
Spectinomycin
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4
Q

How do aminoglycosides work?

A

Inhibit protein biosynthesis by binding the 30S ribo. subunit

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5
Q

Where on the ribosome to aminoglycosides bind?

A

16S rRNA forming the A site.

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6
Q

Specifically, what cellular activities go awry with Aminoglycoside binding

A

Formation of initiation complex
Blockes further translation
Elicits premature termination
Impaired proofreading fxn – nonsense protein formation

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7
Q

Effect of Aminoglycoside caused nonsence proteins

A

Impaired bacterial cell wall function

Damaged membranes let in more aminoglycosides until a full stop is reached

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8
Q

Ultimate long term kill move of aminoglycosides

A

Leakage of ions and disruption of the cytoplasmic membrane

Cell death

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9
Q

Initial entry of positively charged aminoglycosides through the outer membrane

A

Displacement of Mg, Ca ions that form salt bridges with phosphates of the phospholipids in the membrane
This increases permeability

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10
Q

Type of process passage of aminoglycosides through the cytoplasmic membrane is…

A

Active Transport

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11
Q

Three bacterial resistance mechanisms to aminoglycosides

A
  1. Metabolism by acetylation, adenylation, and p-ation
  2. Altered Ribosomes
  3. Altered Aminoglycoside uptake
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12
Q

When bacterial resistance is altered by changes in ribosomes, what happens? Example?

A

16s rRNA binding site altered through point mutations

TB

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13
Q

Main form of reversible and irreversible toxicity associated with aminoglycosides?

A

Irrev – Ototoxicity

Rev – Nephrotoxicity

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14
Q

Consequences of Ototoxicity from aminoglycosides

A

Tinnitus, High Freq hearing loss

Vertigo, Balance Loss, Ataxia

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15
Q

Risk factors for ototoxicity with aminoglycosides?

A

Concurrent use with other ototoxics
Compromised renal fxn
Compromised renal fxn
Genetic vulnerability

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16
Q

Nephrotoxicity with aminoglycosides is precipitated by

A 
Use of loop diuretics
Nephrotoxic antimicrobials (vancomycin, amhotericin)
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17
Q

What to do with appearance of nephrotoxicity or ototoxicity?

A

Stop the drug/Adjust the dose

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18
Q

Very large doses of aminoglycosides can cause what less common side effect?

A 
Curare-like effects
Respiratoy Paralysis (reversed by neostigmine, calcium gluconate)
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19
Q

Why are aminoglycosides often spared as a treatment option?

A

More effective and less toxic alternatives are usually available.

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20
Q

How are aminoglycosides typically provided therapeutically?

A

G-

Given w/ penicillin

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21
Q

Special rules for aminoglycoside penicillin administration

A

Chemical reaction between the two classes of drugs prevent mixture into one solution
Put them in their respective arms

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22
Q

Aminoglycosides/Penicillins combinations treat…

A

Bacterial Endocarditis

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23
Q

Streptomycin is most often used to treat…

A

TB

24
Q

The most important of the aminoglycosides?

A

Gentamicin

25
Q

Gentamicin is used to treat…

A

UTI
Burns
Pneumonias
Joint and Bone Infections caused by G-

26
Q

Aminoglycoside-resistant strains are a big deal.

Who is nobody resistant to…

A

Amikacin

yay Amikacin…

27
Q

What is Streptogramins?

A

Semisynthetic derivatives of Pristinamycin I and pristinamycin II isotlated from Strep. pristinaspiralis

28
Q

What is Synercid?

A

30% quinupristin

70% dalfopristin

29
Q

Why make the synthetic forms of pristinamycins?

A 
Pristinamycins lack suitable solubility for reliably dosages
The derivatives (quinu and dalfo) have amino side chains that allow salt formation and enhance water solubility.
30
Q

Quinupristin and Dalfopristin. Isolated Effect? Synnergistic effects?

A

Bacteriostatic Together

Bactericidal as a mixture

31
Q

How are streptogramins administered?

A

Parenterally

32
Q

How does Dalfopristin work?

A

Blocks Peptidyl transferase (which would normally catalyze formation of a peptide bond between the two AAs present)

33
Q

How does Quinupristin work?

A

Binds in the ribosomal tunnel and causes blockage of the tunnel

“Ribosomal Constipation”

34
Q

Therapeutic use of Synercid

A

VR-Enterococcus faecium bacteremia or UTI (70% success)

Skin infections from MRSA

35
Q

Types of Resistance to Synercid (2)

A
  1. Quin resistance from methylation of A2058 in 23SRNA

2. Efflux and Enzymatic Activation by resistant bacteria

36
Q

What does the prof say has to stop to deal with all the resistance

A

Use of streptogrammins (Virginiamycin) in animal feeeds

37
Q

Side effects of Synercid?

A

No known toxicity

Some SEs –> inflamm/pain at injection site, nausea, diarrhea, muscle weakness, rash

38
Q

Average half life of Synercid/streptogramins?

A

1.5 hours in serum

Linear relationship between the dose and AUC

39
Q

Effects of Synercid/streptogramins on BBB, placental barrier?

A

None

These barriers aren’t penetrated

40
Q

Clearance of Synercid/streptogramins is __% biliary excretion. The remainder leaves through _____

A

75%

Urine

41
Q

Drug interactions of Synercid/streptogramins?

A

They inhibit Cytochrome CYP3A4

Less metab. of warfarin, diazepam, astemizole, terfenadine, cisapride, non-nucleosie RTIs, cyclosporine

42
Q

What do Oxazolidinones do?

A

Inhibit bacterial protein synthesis

43
Q

COmmon Oxazolidinone?

A

Linezolid (Zyvox)

44
Q

Oxazolidinone Mechanism of Action

A

Potent interaction with the 50S ribosomal subunit

Normally, 50S would assocaited with fMet-tRNA to form the 70S. Can’t form 70S with Linezolid.

45
Q

Linezolid interacts specific with…

A

23S rRNA

46
Q

Linezolid is used to treat

A

VR enterococcus faecium
Nosocomial pneumonia caused by MRSA
Skin Infections from MRSA

47
Q

How’s the bioavailabiltiy for Linezolid

A

Excellent oral bioavailability

IV administration

48
Q

Why don’t we treat everything with Linezolid

A

Save the magic bullet

49
Q

Linezolid resistance occurs where/how?

A

Enterococcus
Target site modification
G to U substitution in the peptidyl transferase center of 23S rRNA at position 2576

50
Q

Less serious Side effects of Linezolid?

A

NBD
GI Upset, Vomiting, Diarrhea
Headache, Tongue Discoloration, Candida

51
Q

More serious side effects of linezolid

A

Thrombocytopenia
Gi Bleeding
Anemia
Neuropathy (treatment over 6months)

52
Q

Bioavailability of Linezolid?

A

100% after oral administration

53
Q

Half life of Linezolid?

A

Half-life of 4-6 hours

54
Q

Drug interactions of Linezolid

A

Reversible, nonselective inhibitor of monamine oxidase

Interaction with adrenergic and serotonergic agents

55
Q

Linezolid taking patinets should avoid eating lots of food or beverages that are rich in _______. It will…..

A

Tyramine

cause a significant pressor response

Pharmacology -- Test #2 (13 decks)

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