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Flashcards in Miscellaneous Antibiotics Deck (59)
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1
Q

What is the MOA of tetracyclines?

A

They reversibly bind the 30S ribosome and prevent elongation of the polypeptide by blocking the addition of amino acids.

2
Q

How does resistance to tetracyclines occur?

A
  • Efflux pumps
  • Enzyme inactivation
  • Ribosomal protection
3
Q

What are the pharmokinetics of tetracyclines?

A

Bacteriostatic

***Bactericidal when present at high concentrations against very susceptible organisms

4
Q

What are drugs in the tetracycline class?

A

Tetracycline
Doxycycline
Tigecycline

5
Q

What is the Gram + spectrum of action of tetracyclines?

A
  • Staphylococcus aureus (primarilyMSSA)
  • Streptococcuspneumoniae–PSSP (doxycycline – 83% susceptible)
  • Bacillus spp, Listeria spp,Nocardia spp
6
Q

What is the Gram - spectrum of action of tetracyclines?

A
  • N.gonorrhea and meningitidis
  • Haemophilus influenzae (90% susceptible)
  • Haemophilus ducreyi(chancroid)
  • Campylobacter jejuni
  • Helicobacter pylori
  • Vibrio cholerae, Vibrio vulnificus
  • Burkholderiapseudo mallei
7
Q

What are the holes in coverage of tigecycline?

A

Proteus

Pseudomonas

8
Q

What is the spectrum of activity of tigecycline?

A

Has a wide spectrum of action with notable ones bing MRSA, VRE, S. maltophilia

Gram-Negative Aerobes
• Acinetobacter baumannii
• Aeromonas hydrophila
• Citrobacter spp.
• Escherichia coli
• Klebsiella spp.
• Serratia marcescens
• Stenotrophomonas maltophilia
• NOT Proteus spp or Pseudomonas aeruginosa

Gram-Positive Aerobes
• Staphylococcus aureus • MSSA, MRSA
• Enterococcus spp • VRE, VSE

Anaerobes
• Clostridium perfringens
• Bacteroides spp

9
Q

What should tigecycline NOT be used for?

A

NOT for bacteremias or UTIs

10
Q

How are the tetracyclines best absorbed?

A

On an empty stomach

11
Q

What is the administration method of tetracycline and demeclocycline?

A

Oral

12
Q

What is the administration method of doxycycline?

A

IV and oral

13
Q

What is the administration method of tigecycline?

A

IV only

14
Q

Why aren’t tetracyclines a good choice for UTIs?

A

They don’t concentrate well in the bladder

15
Q

What is the CSF penetration of the tetracyclines?

A

Minimal

16
Q

What is the penetration of the prostate by tetracyclines?

A

Good

17
Q

Is dosage adjustment in renal failure necessary for tetracycline/demeclocycline?

A

Yes

18
Q

Is dosage adjustment in renal failure necessary for tigecycline/doxycycline?

A

No. But adjustment for liver failure must be made for tigecycline

19
Q

Are tetracyclines and tigecycline removed in hemodialysis?

A

No. Only minimally.

20
Q

What are the main uses of the tetracyclines?

A
Respiratory Infection
STDs
RMSF
Q fever
Lyme Disease
Polymicrobial infections (tigecycline)
21
Q

What are the SE of tetracyclines?

A

Nausea
Vomiting
Hypersensitivity
Photosensitivity

22
Q

Why should tetracyclines not be used in pregnant women?

A

Discoloration of permanent teeth and decreased bone growth in children

23
Q

What is the mechanism of sulfonamides?

A

Inhibits dihydropteroate synthetase – which inhibits incorporation of p-aminobenzoic acid (PABA) into tetrahydropteroic acid

24
Q

What are the pharmokinetics of the sulfonamides?

A

Bacteriostatic

25
Q

What is the most frequently used sulfonamide?

A

Sulfamethoxazole (SMX)

26
Q

What is the MOA of trimethoprim?

A

Inhibits dihydrofolate reductase which interferes with conversion of dihydrofolate to tetrahydrofolate

27
Q

What are the PKs of trimethoprim (TMP)?

A

Bacteriostatic

28
Q

Why is Trimethoprim-Sulfamethoxazole used?

A

TMP-SMX has synergistic activity which makes it bactericidal and gives it a broader spectrum of activity.

29
Q

What is the MOA of TMP-SMX?

A

Inhibition to two different steps that lead to purine synthesis

30
Q

What are the MOR to TMP-SMX?

A

􏰀PABA overproduction

􏰀Structural change of dihydropteroate synthetase

􏰀Plasmid mediated production of drug resistant DHPS or decreased bacterial cell wall permeability to sulfonamides

31
Q

What is TMP-SMX the choice treatment for?

A

S. maltophilia

32
Q

How is TMP-SMX administered?

A

Oral and IV

33
Q

Is dose adjustment of TMP-SMX required in renal failure patients?

A

Yes

34
Q

What are the clinical uses of TMP-SMX?

A
  • Acute, chronic, or recurrent infections of the urinary tract
  • Acute or chronic bacterial prostatitis
  • Skin infections due to CA-MRSA
  • Bacterial Sinusitis
  • Nocardia **
35
Q

What are the main SE of TMP-SMX?

A

GI tract problems (nausea, etc)
Leukopenia, thrombocytopenia
Hypersensitivity (many have a sulfa allergy)

36
Q

What is the interaction of TMP-SMX and methotrexate?

A

Decreases the clearance of methotrexate which leads to toxicity

37
Q

What is the MOA of chloramphenicol?

A

Binds to the 50S ribosome to prevent peptide bond formation

38
Q

What are the PKs of chloramphenicol?

A

Bacteriostatic

39
Q

What bacteria does chloramphenicol have bactericidal activity towards?

A

􏰀Haemophilus influenza 􏰀
Streptococcus pneumoniae
􏰀Neisseria meningitidis

40
Q

How does chloramphenicol resistance occur?

A
  • Reduced uptake
  • Ribosome mutation
  • Acetyltransferase inactivation
41
Q

Is dose adjustment for chloramphenicol required in renal failure?

A

No

42
Q

Is dose adjustment for chloramphenicol required in liver failure?

A

Yes

43
Q

Is chloramphenicol active against Pseudomonas?

A

No

44
Q

Is chloramphenicol active against S. aureus or Enterococcus?

A

No

45
Q

What are the main SE of chloramphenicol?

A
  • Gray baby syndrome

- Bone marrow suppression

46
Q

What are some of the specific urinary tract agents?

A

Nitrofurantoin

Methenamine

47
Q

Nitrofurantoin MOA

A

Binds to ribosomal proteins and inhibits translation as well as bacterial respiration and pyruvate metabolism

48
Q

Methenamine MOA

A

Converted in acid pH to ammonia and formaldehyde which is a non-specific denaturant of proteins and nucleic acids

49
Q

How is nitrofurantoin resisted?

A

Production of nitrofuran reductase

50
Q

How is methenamine resisted?

A

No MOR as no formaldehyde resistance has been found

51
Q

What enhances nitrofurantoin absorption?

A

Food

52
Q

Nitrofurantoin Clinical Use

A

􏰀Acute, uncomplicated UTIs

53
Q

Methenamine Clinical Use

A

Suppression or prophylaxis against recurrent UTIs

54
Q

Nitrofurantoin Contraindications

A

􏰀Do not use for:
􏰁 Pyelonephritis
􏰁 Complicated UTI

55
Q

Methenamine Contraindications

A

􏰀Do not use for:
􏰁 Established infections
􏰁 Prophylaxis against catheter-associated UTI
Elderly and those with impaired renal function

56
Q

ElNitrofurantoin Spectrum of Activity

A
E. coli
Citrobacter, sp.
Group B Streptococcus
Staphylococcus saprophyticus
􏰀Enterococcus
(including some strains of VRE)
57
Q

Methenamine Spectrum of Activity

A

NO antimicrobial activity

58
Q

Methenamine SE

A

Generally well tolerated

Can have GI symptoms and a rash though

59
Q

Nitrofurantoin SE

A
  • GI intolerance
  • Rashes
  • Acute pulmonary symptoms – reversible hypersensitivity phenomenon

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