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mrts > C15+16 > Flashcards

C15+16 Flashcards

1
Q

Macrolides

3

A
  • Clarithromycin
  • Azithromycin
  • Roxithromycin
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2
Q

Ketolides

A

Telithromycin

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3
Q

Macrolides MOA

A
  • bacterioSTATIC inhibitors of protein synth. (bind to ribosomes 50s)
  • block transpeptidation
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4
Q

what about macrolides?

A
  • large cyclic lactone ring structures with attached sugars
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5
Q

Clarithromycin Pharmacokinetics

A
  • Elimination: hepatic metabolism and urinary excretion of intact drug
  • 1/2 life: 6h
  • Bioavailability: good oral bioavailability
  • distribution: most body tissues
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6
Q

Azithromycin pharmacokinetics

A
  • absorption is impeded by food (not good oral availability)
  • distribution: the levels achieved in tissues and in phagocytes are higher than those in the plasma
  • Elimination: in urine as unchanged drug
  • 1/2 life: 2-4d
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7
Q

Antimicrobial activity of azithromycin and clarithromycin

A
  • Campylobacter
  • Chlamydia
  • Mycoplasma
  • Mycobacterium avium complex (MAC)
  • Toxoplasma
  • Legionella
  • G+ cocci,
  • some G- organisms
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8
Q

G+ resistance mechanisms

A
  • efflux pump

- production of a methylase –> adds a methyl to the ribosomal binding site

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9
Q

what is special about Azithromycin?

A
  • effective in gonorrhea (alternative to ceftriaxone)

- effective in syphilis (alternative to penicillin G)

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10
Q

Macrolides clinical uses?

A
  • M. pneumoniae
  • Corynebacterium
  • Campylobacter jejuni
  • Chlamydia trachomatis
  • Chlamydophila pneumoniae
  • Legionella pneumophila
  • Ureaplasma urealyticum
  • Bordetella pertussis
  • G+ cocci (except PRSP)
  • beta-lactamase producing staphylo (except MRSA)
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11
Q

special clinical uses of Azithromycin?

[ H&M ;) ]

A

more active against:

  • H influenzae
  • Neisseria
  • Moraxella catarrhalis

also:
urogenital infections caused by
C trachomatis (because of long 1/2 life, single dose is given)

also:
community-acquired pneumonia
(4-d course)

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12
Q

special clinical uses of Clarithromycin

A
  • Prophylaxis treatment of MAC

- component of drug regimens for ulcers caused by H pylori.

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13
Q

Macrolides Toxicity in general

A
  • G.I. irritation (motolin rec. Stim)
  • skin rashes
  • eosinophilia
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14
Q

Clarithromycin toxicity?

A
  • clarithromycin: inhibits several cyt.P450 which can increase the plasma levels of other drugs (ex. anticoagulants, carbamazepine, digoxin, theophylline)
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15
Q

Azithromycin Toxicity?

A
  • azithromycin: The lactone ring structure is slightly different from other macrolides –> drug interactions are uncommon (azithro does not inhibit hepatic cyt.P450)
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16
Q

about Telithromycin?

A

ketolide structurally related to macrolides

17
Q

Telithromycin MOA and spectrum

A

similar to Macrolides but narrower spectrum

18
Q

why we use Telithromycin?

A
  • some macrolide-resistant strains are susceptible to Telithro
  • because it binds more tightly to ribosomes and is a poor substrate for
    bacterial efflux pumps
19
Q

Telithromycin clinical uses?

A
  • used in community-acquired pneumonia (including MDRs)
20
Q

Telithromycin pharmacokinetix

A

eliminated in the bile and the urine

21
Q

Telithromycin Toxicity?

A
  • hepatic dysfunction
  • QTc interval prolongation
  • inhibitor of the CYP3A4 (drug-metabolizing system)
22
Q

Clindamycin MOA

A
  • inhibits bacterial protein synth.
  • binds 50S ribosome
  • block transpeptidation
23
Q

Resistance to Clindamycin ?

A
  • binding site methylation on 50S
  • enzymatic inactivation
  • Clinda has poor penetration through the outer membrane of G- Aerobes!
24
Q

Clindamycin Pharmacokinetix

A
  • distribution: Good tissue penetration after oral absorption
  • metabolism: hepatic
  • Elimination: biliary and renal excretion for both intact drug and metabolites
25
Q

Clindamycin uses?

A
  • severe infections by certain anaerobes (ex. Bacteroides)
  • backup drug against G+ cocci
    (ex. MRSA)
  • prophylaxis of endocarditis in valvular disease patients who are allergic to penicillin
  • against Pneumocystis jirovecii
  • for AIDS-related toxoplasmosis it is used in combination with pyrimethamine
26
Q

Clindamycin Toxicity?

A
  • G.I. irritation
  • skin rashes
  • NEUTROpenia
  • hepatic dysfunction
27
Q

Streptogramins?

A

Quinupristin-dalfopristin

28
Q

Quinupristin-dalfopristin MOA?

A
  • Bactericidal
  • bind to the 50S ribosomal subunit –> constricting the exit channel on the ribosome –> nascent polypeptides are extruded.
  • tRNA synthetase activity is inhibited –> decrease in free tRNA within the cell
29
Q

Quinupristin-dalfopristin activity?

A
  • duration of antibacterial activity is longer than the half-lives of the 2 compounds (postantibiotic effects)
30
Q

Quinupristin-dalfopristin Spectrum?

A
  • penicillin-resistant pneumococci
  • methicillin-resistant (MRSA)
  • vancomycin-resistant staphylo (VRSA)
  • resistant E faecium
31
Q

Quinupristin-dalfopristin administration?

A

I.V.

32
Q

Quinupristin-dalfopristin Toxicity?

A
  • pain
  • arthralgia-myalgia syndrome
    inhibitors of CYP3A4 –> increase plasma levels of drugs
    (astemizole, cyclosporine, diazepam, non-nucleoside reverse transcriptase inhibitors, warfarin)
33
Q

Oxazolidinones?

A

Linezolid

34
Q

Linezolid MOA?

A
  • bacteriostatic

- binds to 50S ribosome –> Block formation of the tRNA-ribosome-mRNA ternary complex –> inhibit initiation

35
Q

Linezolid Spectrum?

A
  • against drug-resistant G+ cocci, including strains resistant to penicillins (eg, MRSA, PRSP) and vancomycin (eg, VRE)
  • against L. monocytogenes and corynebacteria
36
Q

can linezolid be resisted?

A

RARE

37
Q

Linezolid formulation?

A

both Oral and Parenteral

38
Q

Linezolid Pharmacokinetix?

A
  • metabolism: hepatic

- elimination half-life: 4–6 h

39
Q

Linezolid Toxicity?

A
  • in immunocompromised: thrombocytopenia and neutropenia
  • in patients taking selective serotonin reuptake inhibitors (SSRIs):
    serotonin syndrome

mrts (19 decks)

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