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Year II Pharmacology Term 5 > Protein Synthesis Inhibitors > Flashcards

Protein Synthesis Inhibitors Flashcards

1
Q

4 aminoglycosides

A

streptomycin, gentamicin, tobramicin & amikacin

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2
Q

3 tetracycines

A

doxycycline, tetracycline, minocycline

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3
Q

1 lincosamide

A

Clindamycin

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4
Q

1 oxazolidenone

A

Linezolid

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5
Q

Protein synthesis inhibitors are static or cidal

A

Static except aminoglycosides (cidal)

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6
Q

Protein synthesis inhibitors spectrum vs B-lactam

A

Broader than B-lactam

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7
Q

Protein synthesis inhibitors general mechanism

A

ribosomes in eukaryotic cells sufficiently different from bacterial to provide selectivity

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8
Q

Protein synthesis inhibotors tartgiting eleongation

A

Tetracyclines

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9
Q

Target peptide bond formation

A

Clindamycin

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10
Q

Target translocation or termination/recycline

A

Aminoglycosides

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11
Q

Target translocation

A

Macrolides

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12
Q

Action at 30S and 50S subunit of the Ribosome

A

Aminoglycosides

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13
Q

Action at 30S subunit of the Ribosome

A

Tetracyclines

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14
Q

Action at 50S subunit of the Ribosome

A

(i) Macrolides (ii) Clindamycin (iii) Linezolid

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15
Q

Aminoglycosides - streptomycin

Mechanism
SE
Use
Resistance
Kinetics
A

Mechanism
Binds to two receptor sites: one on 16S RNA, and one on 23S RNA; ribosomal proteins involved also
- Wrong amino acids incorporated, i.e. misreading of mRNA (miscoding/30S site)
- Block initiation (streptomycin)
- Block translocation (30S site, other)
- Inhibits recycling (50S binding site)

SE
Deafness
Nephrotoxicity
Bone marrow suppression
Muscle weakness
Use
TB
Anerobic GNR: Gentamicin & tobramycin
GP: SYnergistic with beta lactams
Anaerobes are resistant

Resistance

  • Inactivating enzymes
  • Membrane impermeability
  • Binding site mutation
  • Methylation of rRNA

Kinetics

  • Parenteral administration
  • renal excretion (alter)
  • post antibiotic effect
  • Extended interval dosing release (except in renal dysfunction)
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16
Q

Why are aminoglycosides cidal)

A

Transport into bacterial cells:
Passive diffusion through the porin channels of the outer membrane

Energy-dependent, rate-limiting transport through the plasma membrane (inhibited under anaerobic conditions)

Mech-m of cytotoxicity:
Drug-induced mutated proteins inserted into the plasma membranes enhance uptake of the drug

17
Q

3 drugs with concentration dependent killing

A

aminoglicosides
fluoroquinolones
metronidazole

18
Q

Tetracyclines

Mechanism
Resistance

A

Mechanism
Binds to 30S subunit & blocks amino-acyl-tRNA binding resulting in the elongation block

Resistance

  • Rarely used in USA becuase of resistance
  • Efflux pumps
  • Reduced ribosomal 30 binding site
  • Enzyme inactivation
19
Q

Spectrum for tetracylines

A

Bacteriostatic
Mycoplasma; Chlamydia; Legionella; Rickettsia (Rocky Mtn Fever); Borellia (Lyme disease); Strep pneumonia
Outpatient > hospital
Anti-parasites: malaria prevention

20
Q

Only tetracyline that is hepaticaly cleared instead of renal

A

Doxycycline

Well absorbed from the gut - reduced absorption with food and chelators e.g. Al(OH)3

Good tissue penetration fairly large Vd

21
Q

Tetracyline SE

A

Gastrointestinal intolerance (N/V/D)
Hepatotoxic
Skin photosensitivity
Never use in pregnancy, neonates, children- deposits in enamel of teeth and bone
Doxycycline is the onlytetracycline that can beused in renal failure

22
Q

Drug to avoid giving pregnant women, neonates or childen

A

Tetracycines

23
Q

Macrolids

Mechanism
Resistance mechanism

A

Mechanism
Binds to 50s to block polypeptide release

Resistance
Selectivity and Resistance - role of 23S rRNA- nucleotide 2058

Efflux or reduced permability

Production of esterase
S. pneumoniae or S. aureus

24
Q

Azithromycin (macrolides)

Use & spectrum

A

Bacteriostatic

Bactericidal under certain conditions (organism, site, …)

GPC, Mycoplasma, Legionella, Chlamydia, H. influenzae, Mycobacteria

Can be used in penicillin-allergic individual

Respiratory tract infections

25
Q

Macrolides phamcokinets

A

Well absorbed from GI tract

Widely distributed, concentrated in cells

Hepatic metabolism mainly

26
Q

Macrolides with shortest & longest half lives

A

T1/2: clarithromycin - 3-7 h azithromycin - 68 h (once daily dosing)

27
Q

Macrolides SE/Toxicity

A

Allergy-skin rashes
hepatitis 2-5%
Gastrointestinal upsets (N/V/D)
Ototoxic-especially in elderly

28
Q

Clindamycin

Class
Mechanism

Resitance

Clindamycin pharmacokinetics

Specturm

A

Class
A lincosamide

Mechanism
Binds to the 50S subunit on a 23S rRNA binding site and interferes with the peptide bond formation
Binding site partially overlaps with macrolides

Resistance
Mutual interference if co-prescribed with the macrolides
Resistance mechanisms same as with macrolides

Pharmacockinets
Well absorbed from the gastrointestinal tract
Good tissue penetration (large Vd) concentrated intracellularly
T1/2 2-2.5h
Hepatic metabolism

Spectrum
Bacteriostatic
Narrow spectrum
GPC (Staph. and Strep.); oral and bowel anaerobes (50% Bacillus fragilis)
Often used for deep seated infections (e.g intrabdominal infections) in combination with other agents
Used for skin and soft tissue infection + dental

29
Q

SE of clindamycin

A

Bacteriostatic
Narrow spectrum
GPC (Staph. and Strep.); oral and bowel anaerobes (50% Bacillus fragilis)
Often used for deep seated infections (e.g intrabdominal infections) in combination with other agents
Used for skin and soft tissue infection + dental

30
Q

Linezolid

Class
Mechanism
Resistance
Spectrum
Kinetics
SE
A

Class
Oxazolidinones

Mechanism
Binds to 23S rRNA of 50S at the A site
Blocks formation of the initiation complex

Resistance
Mutation of 23S rRNA binding site
No cross-resistance with other drug classes

Pharmacodynamics and spectrum
Wide range of GP organisms susceptible
Bacteriostatic against staph and enterococci
Bacteriocidal for most strep
Used to treat VRE, VRSA and MRSA
? Potential new agent for Myco. TB

Pharmacokinetics
I/V & oral - 100% oral bioavailability
Renal (30%) and hepatic clearance (65%)

Side Effects/Toxicity 
Hematologic : leukopenia/thrombocytopenia & aplastic anemia
Gastrointestinal intolerance:  N/V/D 
Biochemical hepatitis
Drug interactions: weak MAO-I

Year II Pharmacology Term 5 (9 decks)

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