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Drug Action IV > Lincosamides and Amphenicols (MC) - Block 2 > Flashcards

Lincosamides and Amphenicols (MC) - Block 2 Flashcards

1
Q

What are the lincosamides?

A

Lincomycin and clindamycin

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2
Q

What is the MOA of clindamycin?

A

Inhibits protein synthesis by inhibiting ribosomal translocation on the 50S -> interfering wih aminoacyl translocation

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3
Q

Describe the activity of lincosamides?

A

G+ cooci (CA-MRSA)

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4
Q

Clindamycin hascross resistance with what drug, due to its similar activity?

A

Macrolides

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5
Q

Erythromycin resistance methylase is encoded by?

A

Plasmid-borne gene erm

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6
Q

Describe the SAR of lincosamides?

A
  1. Tertiary amine
  2. Ester formation of 2-OH
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7
Q

Differntiate the esters formed on a lincosamide scaffold?

A

Phosphate -> water soluble
Palmitate -> lipophilic formulation to mask taste for pediatrics

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8
Q

ADRs of Lincosamides?

A
  1. Severe diarrhea with pseudomembranous colitis
  2. Overgrowth of C. diff.
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9
Q

Describe the metabolism of lincosamide?

A
  1. Tertiary amine undergoes N-Demethylation
  2. Sulfur oxidized (S-oxidation)
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10
Q

Describe the penetrability of clindamycin?

A
  1. Gets into the bone
  2. Cross resistance with macrolides
  3. Doesn’t get into the brain or CSF
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11
Q

What is the target level of clindamycin?

A

2-3 mcg/mL

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12
Q

What is the mechanism of chloramphenicol?

A
  1. Inhibits protein synthesis through reversible binding to the 50S of bac ribosome
  2. Inhibits the peptidyl transferase step of protein synthesis
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13
Q

Describe the scope of acitivity of chloramphenicol?

A

G+, G- aerobes and anaerobes

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14
Q

ADR of chloramphenicol?

A
  1. Toxicity: Fatal aplastic anemia (pancytopenia)
  2. GI distubances
  3. Gray baby syndrome (inadequate glucoronidation metabolism)
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15
Q

Resistance of chloramphenicol stems from what?

A

R-factor mediated acetylation of the 1-OH and to a less extent the 3-OH

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16
Q

Types of amphenicols?

A

Chloramphenicol

17
Q

How are chloramphenicols metabolized?

A

Glucoronidation to become for soluble for elimination

18
Q

What is the most common use of chloramphenicol?

A
  1. Rocky mountain spotted fever (Rickettsia)
  2. Menigococcal meningitis with severe b-lactam allergy or Penicillin resistant pneumococcus bacterial meningitis
19
Q

What are the characteristics nitroaromatic?

A
  1. Prodrugs activated by bacteria
  2. Bacteriocidal
20
Q

ADR of nitrroaromatics?

A

Genotoxicity: DNA damage and nicking of ribose

21
Q

Source of nitroaromatic resistance?

A

Inactivation of prodrug activating enzymes

22
Q

What is the active form of nitrofurans?

A

-N-OH

However, N=O and N-O. form radicals that are active as well

23
Q

What is the backbone of a nitrofuran structure?

A

Schiff base

24
Q

Urine color of nitrofurantoin?

A

Dark brown

25
Q

ADRs of nitrofurantoin?

A

N/V
* Avoided by slowing absorption rate and Macrodantin (wax-coated, large particles)

Disulfuram reaction with alcohol

26
Q

Describe the MOA of metronidazole?

A
  1. O free radicals cause oxidative stress and depletes thiol
  2. Reactive intermediate form adducts with protein and DNA -> nicking (DNA fragments)
27
Q

Describe the formulation of methanamine?

A

Drug is active under acidic pH (urine) produces ammonia and formaldehyde
* Ammonia increases pH
* Drug must be given with hippurate and mandelate salts to maintain acidity and from pH getting too high

28
Q

What is the target of fosfomycin?

A

Inhibits the early stages of PG biosynthesis against E. coli and E. faecalis

29
Q

What is the MOA of linezolid?

A

Inhibits protein synthesis by blocking complex between (initiation process): 70S, tRNA, mRNA
* binds to 23S rUnit and prevents the formation of 70S

30
Q

Spectrum of linezolid activity?

A

MRSA, VRE
* May interfere with MAO (serotonin syndrome risk)

31
Q

What causes linezolid resistance?

A

Mutation of 23S rRNA

32
Q

Type of oxazolidinone?

A
  1. Linezolid
  2. Tedizolid
33
Q

How is linezolid metabolize?

A

Synthetic due to morphalene -> hydroxylizes creating an anomeric carbon -> oxidizes to aldehyde breaking the ring open

34
Q

How does tedizolid differ from linezolid?

A

More potent against MRSA and longer half-life due to tetrazole
* Reduce MAO interactions

Drug Action IV (28 decks)

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