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Pharm Exam 2 > Antibiotics 2 - Vancomycin and Macrolides > Flashcards

Antibiotics 2 - Vancomycin and Macrolides Flashcards

1
Q

Vancomycin is what type of compound

A

Glycopeptide

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2
Q

Vancomycin is an inhibitor of…

A

Gram+ cell wall biosynthesis

*BInding of the peptidyl side chain D-ala-D-ala in the peptidoglycan precursor

**Inhibits the transpeptidation required for PG crosslinking

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3
Q

Vancomycin effects and spectrum

A

Bactericidal, effective against Gram + bacteria

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4
Q

What is the threshold for a “susceptible strain” in Vancomycin treatment?

Staph strains that are methicillin resistant are usually inhibited with…

A

MIC of 4 μ/mL

…with MIC of 1-5 μ/mL

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5
Q

VRE is connected to the use of ____

A

Avoparcin

(a glycopeptide AB)

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6
Q

Mechanism of resistance (VRE)

A

Mutation in precursor to PG cell wall

D-ala-D-ala –> D-ala-D-lactate

(1000x less affinity for the lactate one)

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7
Q

Vancomycin potential sides (3)

A

Hypersensitivity response

Nephrotoxicity (.1-1%)

Ototoxicity (rare)

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8
Q

Macrolide AB’s are ________

and _______

A

Macrocyclic lactones

Polyketides (sequential addn of proprionate groups to a growing chain)

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9
Q

Macrolide site of protonation

A

The N on the desosamine sugar

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10
Q

Production of Erythromycin

A

Propriony-CoA

(saccharopolyspora erythrea)

Erythronolide

(Converge with deoxyheose)

Erythromycin

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11
Q

pHa of the amine in erythromycin

A

8.8

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12
Q

The amine in erythromycin can form salts that are more soluble, including ___ and ____

A

Glucoheptonic acid

Lactobiononic acid

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13
Q

During peptide bond formation (transpeptidation), the polypeptide attached to the tRNA in the ____ is transferred to _____

A

polypeptide in the P site is transferred to the amino group of the aminoacyl-tRNA in the A site

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14
Q

Macrolides inhibit protein synthesis by binding _______

A

irreversibly to the P site – inhibiting the translocation from A to P

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15
Q

Macrolide binding involves the bacterial _____ and not _____

A

the bacterial 23S RNA and not the protein

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16
Q

Macrolide may be _____ or _____ depending on _______

A

bacteriostatic

bactericidal

concentration

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17
Q

Macrolides accumulate within ______

A

leukocytes

*transported to site of infection

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18
Q

Four mechanisms of macrolide resistance:

A
  1. Induction of lactone ester hydrolase (degrades by hydrolysis)
  2. Drug induced production of RNA methylase (methylated A2058 prevents eryth from binding to 50S)
  3. Adenine-> Guanine at A2058 (same as above)
  4. Efflux pump (active transport)
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19
Q

Resistance management for macrolides is especially important in regards to…

A

respiratory infections

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20
Q

Intrinsic macrolide resistance organisms

A

Pseudomonas

Enterobacter

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21
Q

Acidic inactivation of the parent molecule (macrolide) is a formation of _________________

A

intramolecular acid-catalyzed ketal formation

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22
Q

Oral erythromycin is administered as ____ or ______

A

enteric coated tablets or more stable salts or esters

23
Q

(Macrolide) Acid stability can be achieved with the ______

A

6-OCH3 derivative

=blocks ketal formation at low pH

–> enhances oral absorption

**this is CLARITHROMYCIN

24
Q

Amine analog that is acid stable

A

Azithromycin

25
Q

Azithromycin structural difference

A

N-methylated methylene-amino moiety replaces the C9 ketone

26
Q

Main route of erythromycin metabolism

A

demethylation in the liver

—> main elimination route is in the bile

27
Q

Erythromycin half life

A

1.5 hours

28
Q

DDI for Erythromycin and clarithromycin

Lower DDI drug?

A

They bind and inhibit 3A4

Dirithromycin has reduced capacity to inhibit p450’s

29
Q

Drugs that interact with macrolides

A
  • Carbamazepine
  • Cyclosporin
  • Disopyramide
  • Midazolam
  • Quinidine
  • Rifampacin
  • Rifabutin
  • Theophylline
  • Triazolam
  • Zidovudine
30
Q

___ and ____ reduce the activity of erythromycin

A

rifampacin

rifabutin

31
Q

Other drugs that can have DDIs with macrolides

A

ergotamine

digoxin

methylprednisone

32
Q

14-membered macrolides stimulate ______

A

GI motor activity

33
Q

Serious allergic/immune responses from macrolides include ___ and ____

A

Steven-Johnson syndrome

Toxic epidermal necrolysis

34
Q

Long term macrolide use can induce…

A

reversible cholestateic hepatitis

35
Q

Erythromycin can increase the probability of ____ in kids whose mothers took the med during pregnancy or breastfeeding

A

pyloric stenosis

36
Q

Erythromycin is inactivated by gastric acids, so all formulations are…

A

given as enteric coated capsules

37
Q

Erythromycin is rapidly absorbed and accumulates in high concentrations within…

A

phagocytes

38
Q

During active ____, large amounts of Erythromycin are released

A

phagocytosis

39
Q

the propionyl ester, lauryl sulfate prodrug of erythromycin

A

Erythromycin estolate

40
Q

2 functions of the propionyl ester group in erythromycin estolate

A
  • makes the drug more lipophilic than erythromycin itself
  • increases oral absorption and blood levels of erythromycin after oral administration
41
Q

Pathophys of the erythromycin induced Cholestatic jaundice

A
  1. The bile becomes granular in the bile duct
  2. Granules impedes bile flow
  3. Bile salts back up into the circulation
42
Q

What must you do if a patient develops cholestatic jaundice while being given erythromycin

A

drug must be replaced by a nonmacrolide antibiotic

43
Q

Erythromycin estolate is contraindicated in

A

patients with preexisting liver disease or dysfunction

44
Q

Erythromycin Estolate is used to treat… (4)

A
  • Beta hemolyric strep
  • Primary siphilis
    • amebic dysentery
  • Viridans endocarditis prophylaxis
45
Q

Erythromycin Ethyl Succinate

  • It is a ______
  • It is more ______ than erythromycin
  • It is used as a ________
A
  • It’s an ethyl succinate ester prodrug
  • It is more lipophilic and orally available
  • it is used as flavored oral suspension for kids
46
Q

Clarithromycin is the ________ of erythromycin

What does this do?

A

the C-6 methyl ether of erythromycin

It blocks ketal formation and makes it more stabile in acid

47
Q

Clarithromycin results in ________ due to reduction of ketals

A

reduced gastric upset

(gastric upset is usually caused by ketal degradation products)

48
Q

Clarith forms a _____ compound

Which is especially good against _____

A

14-(R)-Hydroxy metabolite

H. influenzae

49
Q

Structure of azith: its a ____ ring (why?)

A

15 membered lactone ring

because an N-CH3 group has been inserted between C9 and C10, and the carbonyl Oxygen has been removed

50
Q

Azith half life compared to eryth

A

Longer - terminal half life 68 hours

51
Q

Magnesium / aluminum and Azithromycin?

A

Forms coordination complexes - prevents absorption

52
Q

Major route of elimiation of azithromycin

A
53
Q

Azithromycin has a greater activity against ____ than erythromycin or clarithromycin

A

Gram negatives

54
Q

Most common side effects of azith

A

Diarrhea, nausea, abd. pain

Pharm Exam 2 (12 decks)

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