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KG - Pharmacology > Macrolide Antibiotics > Flashcards

Macrolide Antibiotics Flashcards

1
Q

What part of bacteria do macrolides target?

A

protein synthesis - 50s

G+ most susceptible

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2
Q

prototype macrolide?

A

Erythromycin - oral, IV

targets 50s

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3
Q

top 3 macrolides?

A

Erythromycin - oral, IV
Clarithromycin - oral
Azithromycin - oral, IV

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4
Q

which drug is most similar to erythromycin?

A

clarithromycin

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5
Q

do macrolides bind reversibly or irreversibly to 50s ribosomal subunits?

A

reversibly

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6
Q

are macrolides bacteriostatic are bactericidal?

A
  • bacteriostatic

- concentration/organism dependent - cidal activity

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7
Q

macrolide absorption/excretion/elimination?

A

oral absorption
biliary excretion
fecal elimination

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8
Q

macrolide antibacterial spectrum?

A
  • similar to penicillin G
  • majority of G- organisms are resistant to erythromycin (can’t penetrate the membrane)
  • some S. aureus becoming resistant
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9
Q

what is an alternative therapy for H. pylori?

A
  • clarithromycin + omeprazole (+ ampicillin)
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10
Q

Resistance of macrolides? (erythromycin, clarithromycin, azithromycin)

A
  • efflux pumps

- methylation of drug binding site (ribosome)

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11
Q

toxicity of macrolides? (erythromycin, clarithromycin, azithromycin)

A
  • headache, GI, nausea, vomiting, diarrhea, anal burning
  • mild allergic rxns, urticaria, rashes may occur
  • IV erythro - ototoxicity
  • hepatic changes (jaundice, cholestatic hepatitis, hyperbilirubinemia, abnormal liver function tests)
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12
Q

which macrolide has worst GI side effects? (erythromycin, clarithromycin, azithromycin)

A

erythromycin

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13
Q

which macrolide has least GI side effects? (erythromycin, clarithromycin, azithromycin)

A

clarithromycin

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14
Q

with what drugs do macrolides have drug interactions? what are they?

A

w/ drugs that require CYP3A4
- can inhibit hepatic metabolism of other drugs that require CYP3A4, increasing serum concentrations and potentially causing toxicity

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15
Q

which drug is a potent inhibitor of CYP3A4?

and similar? and least?

A
  • most potent = erythromycin
  • similar = clarithromycin
  • azithromycin = more favorable
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16
Q

what problems were reported w/ macrolide drug interactions?

A
  • serious QT prolongation

- cardiac arrhythmias when erythromycin was coadministered w/ cisapride or pimozide, sparfloxacin or grepafloxacin

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17
Q

macrolide GI side effects (worse to least)

A

erythromycin –> azithromycin –> clarithromycin

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18
Q

macrolide drug interaction (worse to least)

A

erythromycin/clarithromycin –> azithromycin

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19
Q

Which bacteria are better treated with clarithromycin compared to erythromycin? (increased activity?)

A
  • G+ cocci = S. aureus, S. pyogenes, S. pneum
  • G- bacilli = moraxella catarrhalis
  • G-bacilli (other) = LEGIONELLA PNEUMOPHILA, H. flu
  • chlamydia = chlamydia trachomatis
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20
Q

Which bacteria are better treated with azithromycin compared to erythromycin? (increased activity?)

A
  • G- bacilli = moraxella catarrhalis
  • G-bacilli (other) = H. flu
  • chlamydia = CHLAMYDIA TRACHOMATIS
  • mycoplasma = mycoplasma pneumonia
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21
Q

Which bacteria has decreased activity with azithromycin compared to erythromycin? (decreased activity)

A
  • G+ cocci = S. aureus, S. pyogenes, S. pneum
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22
Q

“Azithromycin is an alternative to _____ in treating uncomplicated urethral, endocervical, rectal, or epididymal infections due to Chlamydia.”

A

“Azithromycin is an alternative to TETRACYCLINE in treating uncomplicated urethral, endocervical, rectal, or epididymal infections due to Chlamydia.”

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23
Q

“_________ is the drug of choice for urogenital infections due to Chlamydia occurring during pregnancy.”

A

“ERYTHROMYCIN is the drug of choice for urogenital infections due to Chlamydia occurring during pregnancy.”

24
Q

What is used to treat mycoplasmal pneumonia?

A

Erythromycin or tetracycline

25
Q

What is used to treat syphilis in patients who are allergic to penicillin G?

A

erythromycin

26
Q

What is used to treat the carrier state of corynebacterium diphtheria?

A

erythromycin or penicillin

27
Q

what is used to treat legionairres’ disease?

A

azithromycin

28
Q

what part of bacteria do ketolides target?

A
  • block bacterial protein synthesis
  • bind to TWO sites on 50s ribosomal RNA
  • more affinity w/ macrolides
  • inhibits translation, inhibits prolongation
29
Q

characteristics of Telithromycin (Ketek)?

A
  • BROAD SPECTRUM, first in new family ketolides
  • bacteriostatic
  • resembles macrolides, but more antibacterial activity than macrolides
  • telithromycin binds to a site on bacterial 23S ribosomal RNA of 50S SUBUNIT
30
Q

spectrum of activity of telithromycin?

A
  • good against respiratory pathogens including erythromycin and penicillin resistant pneumococci
  • great activity against intracellular and atypical bacteria
31
Q

dosing of telithromycin?

A
  • oral

- one dose daily is as effective as clarithromycin, trovafloxacin, amoxicillin for some infections

32
Q

how is telithromycin metabolized? half life?

A
  • metabolized by hepatic cytochrome P450 isoenzymes (mostly CYP3A4
  • half life = 9-10 hrs
33
Q

side effects telithromycin?

A
  • DIARRHEA, nausea/vomiting, dizziness
34
Q

contraindication of telithromycin?

A
  • contraindicated in pts with myasthenia gravis
35
Q

what happened during clinical trials/post-marketing with telithromycin?

A
  • reports of serious hepatotoxicity
  • clinical trials in children stopped
  • use for treatment of UTIs
  • remains on market for pneumonia (not DOC, use as macrolide)
36
Q

characteristics of clindamycin?

A
  • reversibly binds to 50S ribosomal subunits
  • inhibits protein synthesis
  • active against wide range of G+ cocci, several anaerobic G- & G+ organisms (G- & enterococci are resistant)
37
Q

is clindamycin bactericidal or bacteriostatic?

A

can be either bacteriostatic or bactericidal depending on:

  • its concentration at site of action &
  • on specific susceptibility of organism
38
Q

dosing of clindamycin?

A
  • oral, parenteral, topical
39
Q

how is clindamycin metabolized?

A
  • metabolized by liver, minimally excreted by kidneys
40
Q

use of clindamycin?

A
  • many species of streptococci (except enterococci), staphylococci are extremely susceptible (MRSA)
  • toxic shock syndrome (use with vancomycin)
  • osteomyelitis - obtains high concentration in bones
  • toxoplasma encephalitis - CSF concentrations are poor, not indicated for treatment of meningitis, however, useful in treating toxoplasma encephalitis
41
Q

toxicity of clindamycin?

A
  • skin rashes, GI disturbances, abdominal pain, nausea, vomiting, diarrhea
  • WELL-KNOWN CAUSE OF PSEUDOMEMBRANOUS COLITIS, overgrowth of Clostridium dificile
  • crosses placenta, distributed into breast milk
42
Q

characteristics of Dalfopristin & Quinupristin?

A
  • individually bacteriostatic, together synergistic & bactericidal
  • STREPTOGRAMINS
  • INHIBITS PROTEIN SYNTHESIS by blocking ribosome function
  • dalfopristin binds to 50S ribosomal particle and inhibits early phase of protein synthesis
  • quinupristin binds to 50S subunit and inhibits late phase of protein synthesis
43
Q

how is dose of Dalfopristin & Quinupristin administered?

A

IV infusion - combo synergistic and bactericidal

44
Q

what is of Dalfopristin & Quinupristin used for?

A
  • vancomycin-resistant Enterococcus faecium bacteremia
  • complicated skin/skin structure infections due to S. aureus (MRSA/MSSA)
  • pencillin resistant S. pneum, MDR streptococci
45
Q

pharmokinetics of Dalfopristin & Quinupristin?

A

synercid administered by IV infusion

46
Q

adverse reactions of Dalfopristin & Quinupristin?

A
  • hepatotoxicity, nausea/vomiting, pain, pruritis, rash

- inhibit P450 drug metabolizing system (CYP3A4), many metabolic interactions (warfarin, diazepam)

47
Q

contraindications of Dalfopristin & Quinupristin?

A
  • breast feeding
  • children
  • hepatic disease
  • pregnancy
  • streptogramin hypersensitivity
48
Q

characteristics of oxazolidinones (LINEZOLID)?

A
  • new class of synthetic antibiotics known as fluorinated OXAZOLIDINONES
  • activity against AEROBIC G+ ORGANISMS
49
Q

mechanism of action of linezolid?

A
  • inhibits protein synthesis
  • binds to site on bacterial 23S ribosomal RNA of 50S subunit
  • prevents formation of functional 70S initiation complex
  • bacteriostatic, except for streptococci it is bactericidal
  • REVERSIBLE, NON-SELECTIVE INHIBITOR OF MONOAMINE OXIDASE (MAO)
50
Q

when to use linezolid?

A
  • G+ infections (bacterial pneum, skin/skin infections, vancomyin resistant enterococcal infections, methicillin resistant staphylococci (MRSA))
  • should be reserved as alternative agent for treatment of infections caused by MDR strains
  • overuse will hasten selection of resistant strains and lead to loss of this agent
51
Q

pharmokinetics of linezolid?

A
  • IV infusion or oral, oral bioavailablity = 100%
  • metabolized via oxidation but oxidative metabolism of linezolid is non-enzymatic and does not involve hepatic microsomal oxidative system
52
Q

adverse reactions linezolid?

A
  • diarrhea 8.3%, headache 6.5%, nausea/vomiting
  • insomnia, constipation, rash, dizziness, fever
  • usual side effects and interaction as MAO inhibitors
  • superinfection can occur
53
Q

contraindication of linezolid?

A
  • hypersensitivity

- pheochromocytoma

54
Q

drug interactions of linezolid?

A
  • beta blockers (IMPORTANT!)
  • general anesthesia
  • local anesthesia (epinephrine)
  • sympathomimetics
  • MAO inhibitors
  • (anything that would increase neurotransmitters)

Also:
- heterocyclic antidepressants (amoxapin, maprotiline, mirtazapine, trazadone, tricyclic antidepressants, SSRIs)

55
Q

main drug of ketolides?

A

telithromycin (ketek)

56
Q

main drug of oxazolidinones?

A

linezolid (zyvox)

KG - Pharmacology (8 decks)

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