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Medical Pharmacology Exam 4 > Protein Synthesis Inhibitors > Flashcards

Protein Synthesis Inhibitors Flashcards

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USMLE® Step 1 flashcards
1
Q

When a drug blocks a reaction that is vital to both

the microbe and host but has greater impact on the microbe, this is referred to as _

A

Selective toxicity

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2
Q

When the small ribosomal subunit and the first tRNA

arriving at the start codon of the mRNA, this described _

A

Initiation

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3
Q

What is the common ribosome subunit shared by both bacterial and mammalian species that accounts for a lot of toxicity when treating with antibiotics?

A

70S ribosome (mitochondrial)

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4
Q

What are the 3 tetracyclines provided as examples? What is their mechanisms of action? What ribosome subunit do they target?

A

Tetracycline
Doxycycline
Minocycline
- Bind the 30s ribosome, prevent binding of tRNA to A site

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5
Q

The selective toxicity associated with the tetracyclines results from its effects on _

A

70S mitochondrial ribosomes

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6
Q

Tetracyclines have [broad/narrow] spectrum, are more active against gram [positive/negative] and are bacteriostatic/bacteriocidal

A

Very broad
Positive
Bacteriostatic

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7
Q

What are the 3 mechanisms by which resistance develops with the tetracyclines?

A

Decreased intracell. levels (e.g. increased efflux)
Enzymatic inactivation of drug
Protein expression that protects target ribosomes

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8
Q

What is the route of administration of the tetracyclines?

A

Oral admin

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9
Q

What are 2 conditions that decrease the absorption of tetracyclines?

A

Divalent / trivalent cations (e.g. dairy)

Increased stomach pH

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10
Q

Tetracyclines have a wide distribution area. In addition to liver, spleen and bone marrow, what 3 notable areas do they accumulate in?

A

Bone
Dentin
Enamel of unerupted teeth

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11
Q

Tetracyclines do/don’t penetrate the CNS

Tetracyclines do/don’t penetrate the placenta

A

Do

Do

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12
Q

Most tetracyclines are cleared by the _ (organ). What is the 2 exceptions? How are they cleared?

A

Kidneys
Docycline - feces
Minocycline - liver - feces

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13
Q

What are 2 major uses for the teracyclines?

A

Lyme disease

Acne

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14
Q

What are 5 side effects associated with the tetracyclines?

A 
GI irritation (pseudomembranous colitis)
Photosensitivity
Hepatotoxicity
Renal Toxicity 
Vestibular disturbance
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15
Q

Why shouldn’t tetracyclines be given to pregnant women or children under 8?

A

Discolors teeth in children

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16
Q

What bacteriocidal antibiotics should not be used in combination with the tetracyclines? Why?

A

Penicillins

Tetracycline alters the bacteriocidal effects of the penicillins

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17
Q

What are 3 known drug interactions of the tetracyclines?

A

Digoxin
Oral anticoagulants (warfarin)
Oral hypoglycemics

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18
Q

How is tigecycline related to tetracycline? What is its mechanism of action?

A

An analogue of tetracycline

Also binds the 30S ribosome, but with higher affinity

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19
Q

What are 2 uses of tigecycline?

A

Tetracycline resistant bugs

Hershey isolate of MRSA

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20
Q

What is the major aminoglycoside provided as an example? What is its mechanism of action

A

Gentamycin

Irreversibly binds the 30S ribosome subunit

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21
Q

The aminoglycosides are [ bacteriostatic / bacteriocidal ] ?

A

Bacteriocidal

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22
Q

What is the antibacterial spectrum of the aminoglycosides? i.e. Gram what is targeted?

A

Mainly gram - aerobes

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23
Q

When combined with aminoglycosides, what to antibiotics act synergistically against S. aureus and S. epidermis?

A

Penicillin

Vancomycin

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24
Q

What are 3 mechanisms by which resistance occurs against aminoglycosides?

A

Mutant ribosome
Decreased uptake / increased efflux
Enzymatic inactivation of drug

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25
Q

What is the major way by which the aminoglycosides are administered?

A

IM or IV

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26
Q

The aminoglycosides are not well distributed to the cells, eyes or CNS. What is one area it accumulates, one of which is associated with major toxicity? How is it cleared?

A

Inner ear ***
Renal cortex
Cleared by kidneys

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27
Q

There are 3 major toxicities associated with the aminoglycosides. They are_

A

Ototoxicity
Vestibular toxicity (vertigo)
Renal toxicity

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28
Q

What is a major factor limiting the use of spreptomycin? When it is used, what is it use for?

A

High resistance

Mycobacterial infections

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29
Q

What is the major use for gentamycin? When not used IV/IM, what is another way to use this drug?

A

Severe gram negative infections

Topically, for burns, wounds, skin lesions

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30
Q

Tobramycin in similar to which aminoglycoside? It is slightly more active against what organism? What is its use in cystic fibrosis?

A

Gentamycin
Pseudomonas
P. aeruginosa respiratory tract infections in cystic fibrosis

31
Q

Amikacin is a semisynthetic, less toxic derivative of _. It us used to treat bugs resistant to _ and _, as well as used to treat what major disease?

A

Kanamycin
Tobramycin and gentamycin
Tuberculosis

32
Q

What aminoglycoside no longer used in the US is similar to gent/tobramycin and less suceptible to enzymatic degradation?

A

Netilmicin

33
Q

A topical aminoglycoside that is limited to topical use because of widespread resistance is _

A

Neomycin / kanamycin

34
Q

Spectinomycin in not an aminoglycoside, but rather it is a _. It works by _. It is [ bacteriostatic/bacteriocidal ]

A

Aminocyclitol
Binding the 30S subunit of the ribosome
Bacteriostatic

35
Q

Regarding its spectrum, spectinomycin works against _

A

Mostly gram - but also some gram + bacteria

36
Q

What are 2 major uses of spectinomycin? How is it administered?

A

MRSA and antibiotic resistant gonorrhea

IM administration

37
Q

What are the 4 examples of macrolide antibiotics provided?

A

Azithromycin
Clarithromycin
Erythromycin
Troleandomycin

38
Q

What is the mechanism by which the macrolide antibiotics work? Are they bactriocidal / static?

A

Reversibly bind the 50S ribosome subunit.

Bacteriostatic

39
Q

What are 3 drug (classes) that should not be used with macrolide antibiotics? Why?

A

Streptogramins
Clindamycin
Chloramphenicol
Site of action very close to each other, competitively inhibit each ther

40
Q

Regarding spectrum, what is the target of the macrolide antibiotics?

A

Narrow, accumulate more in the gram + bacteria

41
Q

How dp erythromycin, clarithromycin and azithromycin compare in their activity against anaerobes?

A

clarithromycin and
azithromycin are more
effective than erythromycin
against anaerobes

42
Q

What are the 3 mechanisms by which resistance develops to macrolide antibiotics?

A

Efflux pumps
Modified bacterial ribosome (methylase)
Drug hydrolysis by esterases

43
Q

True or false, cross resistance is a problem for macrolide antibiotics?

A

True

44
Q

Majority of the macrolides are stable in acid environmets. Which of the macrolide antibiotics is unstable in acid environments? How is this countered?

A

Erythromycin

Admin. orally in stearate and estolate form (tablets)

45
Q

Generally, macrolides have poor penetration of the CNS. Which macrolide is able to penetrate abcesses and placenta?

A

Erythromycin

46
Q

How are erythromycin and clarithromycin excreted?

A

erythromycin- in bile
clarithromycin- metabolized
by liver, secreted by kidney

47
Q

What are 3 main uses for macrolide antibiotics?

A
  • Alternative to penicillin for allergic patients
  • Respiratory infections by atypical microbes (legionella)
  • Common bacterial infections like acne
48
Q

What are 2 major toxicities associated with macrolide antibiotics?

A

GI disturbances

Hepatotoxicity (allergic type cholestatic hepatitis)

49
Q

How are theophilline, warfarin, carbemazepine, astemizole and protease inhibitors related to macrolide antibiotics? Which macrolide is the exception?

A

Macrolides inhibit CYP3A4, potentiating the effect of these drugs
Azithromycin is exception, structurally dissimilar

50
Q

What is the example of a ketolide provided? What macrolide is it related to? What is the mechanism?

A

Telithromycin
Semisynthetic deriv. of erythromycin
Binds the 50 S ribosome in 2 places (blocks protein synthesis)

51
Q

How is telithromycin administered? What enzyme metabolizes it? Under what conditions should adjustments be made to the dose?

A

Oral admin
CYP3A4 50%
Renal insufficiency

52
Q

What do S. aureus and S. pyogenes have to express to be resistant to telithromycin?

A

MLS-B

53
Q

What are 3 main uses of telithromycin?

A

Community acquired RTIs (pneumonia)
Acute bacterial sinusitis
Chronic bronchitis

54
Q

What are 3 common side effecrs associated with telithromycin? What are 3 less common side effects associated with telithromycin?

A

diarrhea, nausea, abdominal pain

visual effects, blurred vision, difficulty focusing

55
Q

What group of patients should not use telithromycin? What are 2 drugs that are known to interact with telithromycin?

A

Myesthenia gravis patients

Cisapride and simvastatin

56
Q

What is the mechanism of action of chloramphenicol? is it bacteriostatic or bacteriocidal? What is its spetrum?

A

Reversibly binds 50S ribosome
Bacteriostatic
Wide - Most anaerobes, most gram -

57
Q

What is the major means by which resistance develops to chloramphenicol?

A

Acetyltransferases modifying the drug

58
Q

How is chloramphenicol administered? Which does it cross, CNS or placenta? Where is it metabolized? How is it excreted?

A

Oral or parenteral
Crosses both
Metabolized in liver, excreted in urine

59
Q

What is a major consideration for the use of chloramphenicol? What drug does it replace (i.e. used only when this drug cannot be used)?

A

Major toxicity

Tetracycline

60
Q

What are 4 major toxicities associated with chloramphenicol?

A

Aplastic anemia
Hematological toxicities
Hypersensitivity
Gray baby syndrome

61
Q

What is the drug associated with gray baby syndrome? What causes this syndrome?

A

Chloramphenicol
Inadequate levels of liver
glucuronyl transferase=> can’t
metabolize the drug

62
Q

Streptogramins are composed of what 2 drugs? How do each of these drugs act individually? Combined?

A

Quinupristin/dalfopristin
Quin - Binds 50S ribosome
Dal - Binds near by
Each bacteriostatic, combined bacteriocidal (synergy)

63
Q

What are 2 major uses of streptogramins?

A

MRSA

Vanco resistant gram positive infections

64
Q

What are 2 associated adverse effects of streptogramins?

A

Pain and phlebitis at IV site

Interaction with CYP enzymes (affects other drugs)

65
Q

Resistance to strpetogramins occurs to each component drug. What are the mechanisms? (2 each)

A 
Quin 
- Methylases to 50S rib (erm)
- lactonases (vgb)
Dal 
Acetyltransferases (vat/sat)
Efflux pumps (vga/vgb)
66
Q

What is the example of the oxazolidinones provided? What is the mechanism of action? How is it administered?

A

Linezolid
bind novel site in 23S ribosomal RNA of the 50S ribosomal subunit
Oral Drug

67
Q

Is linezolid bactriostatic / bacteriocidal? What is it used to treat (3)? What is an advantage it has associated with other protein synthesis inhibitors?

A

Bacteriostatic
MRSA, VREf and multidrug resistant strep. pneumoniae
No cross resistance (different mechanism)

68
Q

What is the example of the lincosamide provided? What is its mechanism?

A

Clindamycin
Binds exclusively to the 50S
subunit of bacterial ribosomes

69
Q

What is the major group of bacteria targeted by clindamycin? Is it bacteriocidal or bacteriostatic?

A

Majority of gram + bacteria

Mainly bacteriostatic, some bacteriocidal activity

70
Q

What is the major mechanism by which resistance to clindamycin develops?

A

Ribosomal methylase (ermA, ermB and ermC)

71
Q

How is clindamycin administered? It has a wide distribution area includin bone. Where is not not able to accumulate in high concentrations? How is it metabolized? How is it excreted?

A

Oral or parenteral
CNS
Liver metabolism
Urine and bile excretion

72
Q

What are 4 uses of clindamycin?

A

Abcesses
Osteomyelitis
MRSA (other group A strep. infections)
RTIs caused by anaerobes

73
Q

What are 4 adverse effects assoc. with clindamycin?

A

Pseudomembranous colitis (C. dificile)
Diarrhea
Skin rash
Stevens-Johnson syndrome

74
Q

How is muciprocin administered? What is it used for? What is its mechanism? How does resistance develop?

A 
Topically administered 
Used to treat impetigo from MRSA or Group A strep 
inhibits
isoleucyl tRNA synthetase
Resistance is rare

Medical Pharmacology Exam 4 (6 decks)

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