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pharmacology -- test #2 > Vancomycin + Macrolides > Flashcards

Vancomycin + Macrolides Flashcards

1
Q

European version of Vancomycin

A

Teicoplanin

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2
Q

What is vancomycin anyway?

A

A nonribosomal glycopeptide antibiotic

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3
Q

How is vancomycin made

A

Fermentation of Nocardia orientalis

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4
Q

Vancomycin mode of action?

A

Inhibitor of G+ cell wall biosynthesis Binds the peptidyl D-Alanyl, D-Alanyl before cross-linking Transpeptidase can’t compete

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5
Q

Vancomycin What does it do

A

Bactericidal against G+ Bacterium with MIC below 4ug/mL

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6
Q

Vancomycin-resistant enterococcal infections came from where

A

Overuse of Avoparcin as a feed additive in European livestock

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7
Q

Mechanism of VRE resistance?

A

Mutation of the peptidoglycan cell wall from D-Ala D-Ala to D-Ala D-Lactate. Vancomycin does not have a strong affinity for this substrate.

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8
Q

Vancomycin toxicity?

A

Potential for a hypersensitivity Response Red skin rash, potential anaphylaxis

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9
Q

Potential Side effects of Vanco?

A

Nephrotoxicity (0.1-1% patients) Ototoxicity Minimized by careful dosing

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10
Q

Structure of Macrolides

A

Macrocyclic lactones (usually 14 membered lactone rings) Polyketides (made by sequential addition of proprionate groups)

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11
Q

How is erythronolide activated?

A

Converge with deoxyhexose biosynthesis Boom – Erythromycin

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12
Q

Secondary Macrolide metabolites are often produced by _____ bacterial stains

A

Streptomyces

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13
Q

The pKa of the amine in erythromycin is….. So what?

A

8.8 Can form salts that are more soluble

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14
Q

How do Macrolides stop bacteria?

A

Binding reversibly to the P site of the bacterial ribosome Inhibited translocation of peptidyl-tRNA from A to P

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15
Q

Macrolide binding mainly involves which bacterial ribosome subunit?

A

23S RNA

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16
Q

What cell do macrolides tend to accumulate in? So fucking what?

A

Macrophages Delivered to sites of infection

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17
Q

Four mechanisms of Macrolide resistance

A
  1. Lactone ester hydrolase hydrolyzes macrocycle 2. RNA methylase 3. Mutation of A->G at A2058 (erythro can’t bind it anymore) 4. Efflux Pump ejects drugs from the cell by active transport
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18
Q

What does RNA methylase do to promote Macrolide resistance

A

Methylates A2058 on the 23S ribosome RNA molecules of the 50S subunit. No binding to 50S subunit

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19
Q

Why don’t erythromycin-producing organisms have toxic effects from their byproduct?

A

They use the ribosomal methylation technique to protect themselves.

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20
Q

How do pseudomonas and enterobacter protect themself from macrolides?

A

Intrinsic resistance/Not allowing entry

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21
Q

Why is oral erythromycin administered with enteric coated tablets?

A

Parent molecule inactivated in acid

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22
Q

Problems with acid inactivated erythromycin?

A

Inactive, Produces GI cramping

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23
Q

How can you get that erythromycin to be stable in acid (by turning it into Clarithromycin)?

A

6-OCH3 derivative, which enhances oral absorption Blocks ketal formation You just made Clarithromycin!

24
Q

How can you get erythromycin to be stable in acid (by turning it into Azithromycin)?

A

An N-methylated methylamino moiety replaces the C-9 ketone Can’t make a ketal anymore

25
Q

Main route of erythromycin metabolism?

A

Demethylation in the Liver Eliminated in Bile (small portion in urine)

26
Q

Erythromycin half life

A

1.5 hours

27
Q

Erythromycin and clarithromycin both bind and inhibit which CYP

A

CYP 3A4

28
Q

Drug interactions of Azithromycin?

A

None

29
Q

Macrolides (other than Azithro) tend to cause drug reactions with which specific drugs

A

Carbamazepine Cyclosporin Disopyramide Midazolam Quinidine Rifampicin Triazolam and a bunch of others. 3A4 does a lot of shit…

30
Q

Macrolide side effects.

A
  • Relatively Safe - Stimulate GI motor activity (Vomiting, Cramps, Ab Pain) - Minor/Major Allergic Rxns - Stevens-Johnson Syndrome - Cholestatic Hepatitis (Jaundice, cramping, nausea, fever) - Pyloric stenosis in children of moms taking drug
31
Q

How is erythromycin given orally

A

Enteric Coated capsules More stable salts, esters

32
Q

Erythromycin estolate is a ____ ester. It is a _______ of erythromycin

A

Propionyl Lauryl sulfate prodrug

33
Q

Purpose of the propionyl ester on Erythromycin estolate?

A

Drug is more lipophilic than erythro. alone Increased oral absorption and blood levels after admin.

34
Q

What happens in Erythromycin estolate cholestatic jaundice

A

Bile becomes granular in duct Impeded flow Salts back into circulation No more macrolides after this

35
Q

Erythromycin estolate is contraindicated for..

A

Patients with preexisting liver disease/dysfunction

36
Q

Erythromycin estolate is used to treat…

A

Group A beta-hemolytic strep

Primary Syph

Amebic Dysyntery

Prophylactically to stop endocardiditis from viridans

37
Q

What is Erythromycin Ethyl Succinate?

A

An ethyl succinate ester prodrug of erythromycin

38
Q

Advantage to Erythromycin Ethyl Succinate?

A

Ethyl succinate ester makes the drug more lipophilic and increases absorption from oral admi

39
Q

How is Erythromycin Ethyl Succinate typically used?

A

Flavored oral suspension for pediatric patients

40
Q

Relationship of Clarithromycin and Erythromycin

A

Cl is the C6 methyl ether of Ery Blocks ketal formation, increased stability

41
Q

Fun fact about Clarithromycin metabolites…

A

The 14-R-hydroxy metabolite of Clarithromycin has greater antibiotic activity than Clarithromycin

42
Q

The 14-R-hydroxy metabolite of Clarithromycin is especially effective against…

A

H. influenzae

43
Q

Clarithromycin. Mechanism of administration

A

Oral suspension Tablets Extended-release tablets

44
Q

How does Azithromycin prevent cyclic ketal formation?

A

Removal of Carbonyl Oxygen, Addition of N-ch3 group

45
Q

Relationship between Azithromycin and Erhythromycin half lives. So what?

A

Azi – 68 hours Ery – 1.5 hours Infrequent doses help out with noncompliant patients

46
Q

The concentration of Azithromycin in the tissue can up over ____ times higher than in the plasma

A

50

47
Q

What might form complexes with Azithromycin that prevent absorption?

A

Magnesium Aluminum

48
Q

Major route of Azithromycin elimination?

A

Biliary Over about a week, 6% appears as unchanged drug in the urine

49
Q

Azithromycin is especially active against…

A

G- Better than erythromycin, clarithromycin

50
Q

Most common side effects of Azithromycin

A

Diarrhea Nausea Ab Pain Vomiting

51
Q

Identify.

A

Vancomycin

52
Q

Identify

A

Erythromycin Estolate

53
Q

Identify.

A

Erythromycin Ethyl Succinate

54
Q

Identify.

A

Clarithromycin

55
Q

Identify.

A

Azithromycin.

pharmacology -- test #2 (13 decks)

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