Sulfonamides

Question 1

Sulfonamides MOA

Answer 1

Block dihydropteroate synthase

- necessary for bacterial synthesis of folate for production of thymidine for DNA

Question 2

Sulfonamides 3

Answer 2

Sulfamethoxazole (SMX)
Sulfisoxazole
Sulfadiazine

Mimic PABA and competitively inhibit dihydropteroate synthase

Question 3

Sulfonamides resistance

Answer 3

Increased PABA

alter dihydropteroate synthase

Decrease uptake

Question 4

Dapsone

Answer 4

NOT sulfonamide but competes with dihydropteroate synthase

Mycobacterium leprae (leprosy)
Pneumocystis jiroveci

TRIGGERS HEMOLYSIS IN G6PD

Question 5

Sulfonamide use 3

Answer 5

1. SMX TMP- sequential block of THF synthesis
2. Sulfadiazine- silver cream for burns
3. Sulfadiazine and pyrimethamine- sequential THF block, used in Toxoplasmosis (HIV)

Question 6

Sulfonamide Toxicity

Answer 6

PHOTOSENSITIVITY- drug interacts with UV light

TRIGGERS HEMOLYSIS IN G6PD

BINDS ALBUMIN AND displace warfarin (high INR) and bilirubin- risk of kernicterus in infants

Hypersensitivity reactions (same as PCN)
SJS/TEN
anaphylaxis 
Maculopapular rash
Serum sickness (fever, rash, arthritis)
Interstitial nephritis

Question 7

Trimethoprim/Pyramethamine MOA

Answer 7

Inhibits dihydrofolate reductase

Question 8

Trimethoprim/Pyramethamine toxicity

Answer 8

Can inhibit human DHF reductase:
Bone marrow suppression- pancytopenia- megaloblastic anemia, leukopenia, low platelets

Can alleviate with leucovorin (folinic acid)

Question 9

TMP SMX use

Answer 9

UTIs

Pneumocystis PNA in HIV- Tx and prophylaxis- very high rate of hypersensitivity reactions

Question 10

Do not use this TMP SMX in pregnancy

Answer 10

Risk of kernicterus and disrupts folate metabolism

Sulfonamides displace drugs (warfarin) and BILIRUBIN from albumin- kernicterus in infants