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Pharmacology > Exam 8: Sulfonamides > Flashcards

Exam 8: Sulfonamides Flashcards

1
Q

Name 2 Oral Sulfonamides

A

Sulfadiazine

Sulfamethoxazole

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2
Q

Name 1 Topical Sulfonamide

A

Silver sulfadiazine

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3
Q

Name 1 Pyrimidine

A

Trimethoprim

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4
Q

Name one popular sulfonamide combination product

A

Trimethoprim-Sulfamethoxazole

Bactrim

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5
Q

What is the mechanism of Sulfonamides?

A

Inhibition of bacterial Folate synthesis
Via competitive inhibition of Dihydropteroate Synthase
They do this by mimicking PABA

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6
Q

Are Sulfonamides -cidal or -static?

A

Bacteriostatic

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7
Q

What is an advantage of combining a sulfonamide with trimethoprim?

A

The combo is bactericidal, rather -static

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8
Q

What is the mechanism of Trimethoprim?

A

Inhibition of bacterial folate synthesis

Via inhibition of Dihydrofolate Reductase

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9
Q

What is Folate?

A

Vitamin B9
Required for DNA synthesis
Bacteria produce it, humans have to consume it.

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10
Q

What is folate deficiency most associated with?

A

Birth defects
Neural tube defects
Also megaloblastic anemia

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11
Q

What is an important consideration with any drug that his antifolate properties?

A

They all have teratogenic potential, at least in principle.

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12
Q

What types of organisms are susceptible to Sulfonamides? Resistant?

A

Organisms that produce their own folate

Those that obtain pre-formed folate

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13
Q

What are 4 resistance mechanisms to Sulfonamides?

A
  1. Mutated dihydropteroate synthase (lowered affinity)
  2. Increased efflux (Pseudomonas)
  3. Plasmids with drug-resistant enzymes (enteric gram negatives) Leads to MDR
  4. Auxotrophy for folate (E. faecalis)
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14
Q

What is the mechanism of resistance to sulfonamides for E. faecalis?

A

Auxotrophy for Folate

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15
Q

What is a common mechanism of sulfonamide resistance for Pseudomonas?

A

Increased drug efflux

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16
Q

What is a mechanism of resistance to Sulfonamides that leads to MDR?

A

Plasmids with drug-resistant enzymes

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17
Q

What happens to Sulfasalazine in the gut? What happens to each metabolite?

A

Metabolism to sulfapyridine and 5-ASA
5-ASA has topical anti-inflammatory effects
Sulfapyridine has a systemic anti-inflammatory effect

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18
Q

What Sulfonamide is used in burn therapy?

A

Silver Sulfadiazine

Topical (applied as cream)

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19
Q

What happens to the silver and the sulfa that is topically applied to burns?

A

They are both anti microbial
Sulfa gets absorbed
Silver does not get absorbed

20
Q

How long is the half-life of Sulfadoxine? Why?

A

7-9 days (Really long)

Probably because of protein binding

21
Q

What sulfonamide could be used in malaria? Why is its use limited?

A

Sulfadoxine combined with pyrimethamine

Limited by severe side effects and resistance

22
Q

How do sulfonamides circulate in the plasma?

A

Bound to albumin to varying degrees

23
Q

How do Sulfonamides distribute in the body?

A

Pretty much everywhere
Cross BBB
Cross placenta, enter breast milk
Pregnancy Category C

24
Q

Why doesn’t Trimethoprim affect human cells, since we do have DHFR?

A

100,000x more affinity for bacterial DHFR

25
Q

What is a mechanism of resistance to Trimethoprim?

A

Altered DHFR enzyme

26
Q

How does Trimethoprim’s volume of distribution compare to Sulfonamides?

A

9x higher

27
Q

How is Trimethoprim removed from the body?

A

Excreted unchanged in the urine

28
Q

What ratio is dosing for TMP:SMX?

A

1:5 (more sulfa)

Results in 1:20 ratio in plasma concentration

29
Q

What is a scary bug that is usually susceptible to TMP-SMX?

A

Community acquired MRSA

30
Q

What are some bugs that are resistant to TMP-SMX?

A 
Ineffective against
Bacteroides fragilis, most
anaerobes, P. aeruginosa,
M. tuberculosis, T. pallidum,
Campylobacter, penicillin-
resistant pneumococci, and
rickettsiae
31
Q

What is a super common use for TMP-SMX?

A

UTIs (E. coli)

32
Q

What is a weird organ that sulfonamides are able to penetrate?

A

Prostate

Useful in prostatitis

33
Q

What bug causes most uncomplicated UTI? Complicated?

A

Uncomplicated: E. coli
Complicated: Probably still E. coli, but some E. faecalis too

34
Q

Treatments for complicated vs uncomplicated UTIs?

A

Both use TMP-SMX
Days for uncomplicated
2 weeks for complicated

35
Q

Definition of complicated UTI?

A

Any UTI in a male

Or associated with a predisposing lesion

36
Q

What could you use for a UTI with resistance to TMP-SMX?

A

Fluoroquinolones

37
Q

What are 3 GI bugs that can be treated with TMP-SMX?

A

Salmonella
E. coli (traveler’s diarrhea)
Listeria monocytogenes

38
Q

What are 4 atypical/rare infections treatable with TMP-SMX?

A

Nocardia (esp with immunocompromise)
Toxoplasmosis
Pneumocystis j.
Yersenia (Plague)

39
Q

Cats are a buzzword for…

A

Toxoplasmosis

Pregnant women should be careful

40
Q

Two big reasons sulfonamides aren’t used more often?

A

Side effects can be bad

Resistance is common

41
Q

Sulfonamide adverse effects?

A

Skin rashes/hypersensitivites
Crystalluria
Hyperkalemia (TMP reduce renal K secretion)
Acute Hemolytic anemia related to G6PD deficiency
Agranulocytosis, aplastic anemia

42
Q

What is a big predisposing factor to Sulfa hypersensitivity reactions?

A

HIV

43
Q

What condition can predispose patients to non-immune hemolysis?

A

G6PD deficiency (oxidative stress)
Most common enzyme deficiency worldwide
X linked
Sulfa drugs are more likely to cause anemia in these patients

44
Q

Sulfonamide drug interactions?

A

Interfere with other drugs that bind albumin

Warfarin, phenytoin, sulfonureas

45
Q

Who should avoid Sulfonamides when possible?

A

Pregnant women
Pregnancy Category C
Especially avoid them in the first trimester ***
Less of a concern late in pregnancy

46
Q

Other than teratogenesis, what else can sulfonamides cause in the fetus?

A

Kernicterus (hyperbilirubinemia causing neurologic problems)

Related to albumin binding/bilirubin binding to albumin

Pharmacology (34 decks)

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