Sulfa

Question 1

Source

Answer 1

Synthetic.

Question 2

Chemistry

Answer 2

structurally like Para Amino Benzoic Acid (PABA).
prevents the formation of folic acid

Question 3

Folic acid form?

Answer 3

Protein and DNA synthesis

Question 4

Absorption

Answer 4

*Complete oral absorption is classified into:
1- Short Acting (Rapidly excreted): are given every 6 hours
2-Intermediate Acting: are given every 12 hours
3- Long Acting: are given every 24 hours
*Poor oral absorption
*Topical sulfonamides: cream and powder

Question 5

Distribution

Answer 5

They pass BBB and placental barrier

Question 6

Fate

Answer 6

They are partly excreted unchanged in urine (are used in treatment of UTIs, impairment, and are more soluble and more active in alkaline urine), and partly metabolized in the liver by acetylation. The acetylated metabolite is inactive and insoluble in acidic urine leading to crystalluria

Question 7

Action on bacteria

Answer 7

bacteriostatic.

Question 8

Mechanism of Action

Answer 8

Sulphonamides compete with bacterial PABA (due to structural similarity) for bacterial dihydropteroate synthetase (DHPS) leading to inhibition of folic acid synthesis.

Question 9

Antibacterial activity

Answer 9

1.Overproduction of PABA,
2.Decreased sensitivity of DHPS to sulfa BUT NOT to PABA
3.Utilization of preformed folic acid.

Question 10

Adverse effects

Answer 10

1. Hypersensitivity reactions: rash, photosensitivity, urticaria (Stevens-Johnson
   syndrome)
2. idiosyncratic hemolytic anemia in patients with favism due to G-6-PD deficiency.
3. Cross allergy between sulfonamides and thiazides
4. Crystalluria due to precipitation of acetylated metabolites in acidic urine
5. Highly bound to plasma protein, which results an elisplaying other e drugs which causes Serious toxic effects of such drug
6. Displaces biliubin and causes Jaundice

Question 11

Contraindication

Answer 11

1,Allergy to sulfonamides and thiazide
2. Favism.
3. Newborn, pregnancy and lactation

Question 12

Trimethoprim (TMP) (m.o.a)

Answer 12

inhibits synthesis of folinic acid (Active folic acid).

Question 13

Co-Trimoxazole(M.O.A)

Answer 13

Sequential block of DHPS and DHFR that inhibits synthesis of folinic acid

Question 14

Formation Co-Trimoxazole

Answer 14

Sulphamethoxazole and TMP

Question 15

Co-Trimoxazole Spectrum and indications:

Answer 15

Similar to sulfa and TMP but more potent and broad
Treatment of mixed infection
Reduces toxicity Caused by each drug alone

Question 16

Achieves synergism:

Answer 16

each drug alone is bacteriostatic but co-trimoxazole is bactericidal