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Antibiotics > Sulfonamides & Trimethoprim > Flashcards

Sulfonamides & Trimethoprim Flashcards

1
Q

T/F
All sulfonamides are similar in structure to para-aminobenzoic acid (PABA).

T/F
PABA is a precursor required by bacteria for folic acid synthesis.

T/F
Sulfonamides may have an increased affinity for the enzyme than the natural substrate, PABA.

A

TRUE

TRUE

TRUE

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2
Q

What is the mechanism of action for Sulfonamides?

A
  • Bacteria require tetrahydrofolic acid (derivative of folic acid), as a cofactor in the synthesis of thymidine, purines, and, ultimately DNA.
  • Bacterial cell walls are impermeable to folic acid. Bacteria must synthesize it from PABA.
  • Because of the sulfonamides structural similarity to PABA, they compete with PABA for the enzyme dihydropteroate synthetase; thus, depriving the cell of tetrahydrofolic acid.
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3
Q

Why aren’t host cells affected by Sulfonamides?

A

Require preformed folic acid; they cannot synthesize folic acid. Therefore they don’t use PABA.

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4
Q

Sulfonamides are Bacteriocidal or Bacteriostatic?

A

BACTERIOSTATIC

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5
Q

How are sulfonamides primarily excreted?

What application does that have on their use?

A

glomerular filtration

Good for UTIs

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6
Q

What adverse reactions are associated with sulfonamides?

A

Nephrotoxicity

Kernicterus (if given in 3rd trimester)

Anaphylaxis (sulfa allergy)

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7
Q

Why don’t you want to give Sulfonamides to a pregnant (3rd trimester) patient with UTI?

A

Kernicterus (brain damage) occurs in neonate who has increased unconjugated bilirubin in blood

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8
Q

What bugs are covered by Sulfonamides?

A

Staph.
Strep.
Bacillus anthracis

Haemophilus spp. 
Providencia 
Salmonella 
Shigella
PEK
CE
Atypicals:
Nocardia asteroides
Chlamydia trachomatis 
Toxoplasma gondii 
Plasmodium falciparum
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9
Q

What G+ bugs are covered by Sulfonamides?

A

Staph.
Strep.
Bacillus anthracis

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10
Q

What G– bugs are covered by Sulfonamides?

A

Haemophilus spp.
Providencia
Salmonella
Shigella

PEK

CE

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11
Q

What Atypical bugs are covered by Sulfonamides?

A

Nocardia asteroides
Chlamydia trachomatis
Toxoplasma gondii
Plasmodium falciparum

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12
Q

What ABX might you use for the following indications:

  • Uncomplicated UTI
  • Pneumocystis carinii (treatment and prophylaxis)
  • Nocardosis
  • Toxoplasmosis
  • Malaria (chloroquine-resistant)
  • Rheumatic fever prophylaxis (pcn allergic)
A

Sulfonamides

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13
Q

What 3 mechanisms do microorganisms use for sulfonamide resistance?

A
  • Overproduction of PABA
  • Decreased permeability of the bacteria to the drug.
  • Structural change in dihydropteroate synthetase resulting in decreased affinity for the sulfonamide
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14
Q

Is Trimethoprim Bacteriocidal or Bacteriostatic?

A

BACTERIOSTATIC

bactericidal with high concentrations

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15
Q

What is the Trimethoprim mechanism of action?

A
  • Inhibits dihydrofolate reductase thus preventing the formation of tetra hydrofolic acid.
  • 50,000x more active against bacterial dihydrofolate reductase than human enzyme
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16
Q

T/F

Trimethoprim targets the same enzyme (dihydrofolate reductase) as methotrexate, the cancer drug.

A

TRUE

17
Q

How are sulfonamides primarily excreted?

What application does that have on their use?

A

glomerular filtration

Good for UTIs

18
Q 
Why must you be careful providing Trimethoprim to:
• Alcoholics
• Pregnant women
• Debilitated ptns
• Malabsorptive syndromes
A

Folate Deficiency

19
Q

What bugs are covered by Trimethoprim?

A

Staph.
Strep.
Bacillus anthracis

EK

SPCE

Pneumocystis carinii**

20
Q

What G+ bugs are covered by Trimethoprim?

A

Staph.
Strep.
Bacillus anthracis

21
Q

What G– bugs are covered by Trimethoprim?

A

EK

SPCE

22
Q

What Atypical bugs are covered by Trimethoprim?

A

Pneumocystis carinii**

23
Q

What ABX might you use for the following indications:

  • Acute Uncomplicated UTI
  • Recurrent UTI prophylaxis
  • Traveler’s diarrhea (treatment and prophylaxis)
A

Trimethoprim

24
Q

What is Bactrim made up of?

A

Trimethoprim + Sulfamethoxazole

25
Q

Is Trimethoprim+Sulfamethoxazole (Bactrim) Bacteriocidal or Bacteriostatic?

A

BACTERIOCIDAL

26
Q

T/F
Mechanism Of Action of Trimethoprim+Sulfamethoxazole (Bactrim) is Combined mechanisms of both agents (synergistic); bactericidal and thought to reduce the rate of emergence of resistance.

A

TRUE

27
Q

T/F

Bugs covered by Trimethoprim+Sulfamethoxazole (Bactrim) is a combination of those from the two separately.

A

TRUE

28
Q

What is the drug of choice for Strenotrophamonas maltophilia?

A

Trimethoprim+Sulfamethoxazole (Bactrim)

29
Q

Why won’t you prescribe Trimethoprim+Sulfamethoxazole (Bactrim) to a patient on Warfarin?

Why won’t you prescribe Trimethoprim+Sulfamethoxazole (Bactrim) to a patient on Methotrexate?

A

Likely to Potentiate anticoagulant effects

Displace methotrexate from protein binding sites, resulting in an increase in free methotrexate concentrations

Antibiotics (25 decks)

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