Sulfonamides

Question 1

Name the sulfonamides

Answer 1

Sulfisoxazole
Sulfadiazine
Sulfamethoxazole
Sulfazalazine
Sulfadoxine

Question 2

How do sulfonamides work?

Answer 2

Inhibit folate production and incorporation into purines and prevents DNA synthesis

Question 3

What are the indications for sulfonamides?

Answer 3

UTI’s
Otitis media
Upper respiratory infections
Soft tissue infections

Question 4

Are sulfonamides bacteriostatic or bacteriocidal?

Answer 4

Bacteriostatic

Cidal in combination with trimethoprim

Question 5

Sulfonamides inhibit ….

Trimethoprim inhibits…

Answer 5

Sulfonamides inhibit dihydropteroate synthase

Trimethoprim inhibits folate reductase

Question 6

Sulfonamides are a structural analog of…

Answer 6

PABA

Question 7

Which sulfonamide is used in malaria?

Answer 7

Sulfadoxine combined with pyrimethamine

Question 8

Which sulfonamide has the longest half life?

Answer 8

Sulfadoxine (7-9 days)

Question 9

Which sulfonamides have short half lives?

Answer 9

Sulfasalazine, Sulfisoxazole

6-10 hours

Question 10

Which sulfonamide remains in the lumen?

Answer 10

Sulfasalazine

Question 11

Which sulfonamides have intermediate half-lives?

Answer 11

Sulfadiazine (10-17 hours)

Sulfamethoxazole (+ Trimethoprim) (11 hours)

Question 12

Which sulfonamides are oral OR IV?

Answer 12

Sulfadiazine

Sulfamethoxazole+Trimethoprim

Question 13

Which sulfonamide is topical use?

Answer 13

Sulfacetamide

Question 14

What counseling point should be made with sulfonamides?

Answer 14

Stay hydrated!!

Drug could crystallize in the urine

Question 15

How are sulfonamides excreted?

Answer 15

In the urine - 10 to 20 times concentrated compared to the plasma

Question 16

Why is sulfasalazine different?

Answer 16

It’s poorly absorbed and metabolized in the gut to sulfapyridine and 5-aminosalicyclic acid (anti-inflammator)

Used in Ulcerative collitis, inflammatory bowel disease, surgery, and arthritis

Question 17

What toxicities are associated with sulfonamides?

Answer 17

ALlergic reactions, ranging from mild to severe

Mild - fever, rash, photosensitivity, uticaria
Severe - conjunctivities, exfoliative dermatitis, Stevens johnson syndrome

Urinary tract - drug can crystallize in acidic urine, keep it alkylated by staying hydrated

Hematopoietic disturbances - hemolytic anemia, electrolyte abnormalities

Question 18

What are the 4 types of allergic reactions? What do sulfonamides cause?

Answer 18

Type 1 - anaphylaxis (penicillins)
Type 2 - cytotoxic (penicillins)
Type 3 - Immune complex mediated response (Sulfonamides!)
Type 4 - cell mediated response (TB skin test, poison ivy)

Question 19

Why do sulfonamides cause Hematopoietic disturbances?

Answer 19

Decreased glucose-6-phosphate can cause hemolytic anemia

Decreased potassium and magnesium can cause electrolyte abnormalities

Question 20

What drug interactions do we worry about with sulfonamides?

Answer 20

Plasma binding (competition)
Compete for acetylation enzymes

Question 21

What causes resistance in sulfonamides?

Answer 21

Plasma mediated
Altered enzyme affinity, increased affinity for PABA

Loss of permeability through membrane

Increased production of PABA (up to 70 times more PABA in some resistant bacteria)

Question 22

What is trimethoprim?

Answer 22

Trimethoprim inhibits dihydrofolate reductase

Often combined with sulfonamide Sulfamethoxazole in Bactrim/Septra in 5:1 ratio (20:1 ratio in blood)

Question 23

What is trimethoprim used for?

Answer 23

Combo product of trimethoprim/sulfamethoxazole is used in:

UTI’s
Otitis media
Bronchitis
Used to treat pneumocystis jiroveci in AIDs patients

Question 24

What benefit does septra have over penicillins?

Answer 24

Oral suspension doesn’t need refrigeration

Question 25

What toxicities are associated with trimethoprim?

Answer 25

Hematopoietic problems if folate deficient
GI disturbances
Hepatitis
Exfoliative dermatitis