Sulfonamides

Question 1

Sulfonamides MOA

Answer 1

• bacteriostatic

- Compete with PABA in the synthesis of folic acid for DNA (purine) synthesis

Question 2

Sulfa Sensitive Organisms

Answer 2

Actinomyces
Chlamydia 
Ecoli 
Group A step
H. Influenze 
MRSA
Norcardia
Staph Aureus
Toxoplasma gondii 

– protozoa, and pneumoncystitis jirovecii

Question 3

Sulfa resistance organisms

Answer 3

Rickettsia, fungi, molds, mycobacterium tuberculosis, spirchetes

Question 4

Tx with sulfa drugs

Answer 4

UTI (first attack and prophlyxsis)
Norcardiosis
toxoplasmosis and trachoma
Pneumocystits carnii

Question 5

Development of resistance to sulfa drugs

Answer 5

1. decreased sensitivity of the target enzyme
2. increased formation of PABA
3. use of exogenous folate

Question 6

Tx with sulfa drugs

Answer 6

DOC for norcadosis

• UTI
• Toxoplasmosis
• Trachoma
• Pneuomocystits carinii infections in children and AIDs pts

Question 7

Sulfa drug metabolism

Answer 7

acetylated in the liver (loss of antibacterial action- become insoluble and can cause crystalluria and renal damage if they precipitate out- more common in renal failure pts and dose should be reduced)
excreted in the kidney

Question 8

Sulfa drug toxicities

Answer 8

1. Protein bound- can displace other protein bound drugs (phenylbutazone, anticoagulants, phenytoin, methotrexate) and cause related toxicities
2. Kerniceterus in the nursing infant- displace protein bound bilirubin - CI in infants less than 2 months of age
3. Blood dyscrasia, pancytopenia, agranulocytosis etc
4. Microscopic hematuria
5. Kidney and liver damage - mostly because of crystalloids
6. Peripheral Nerve damage in G6PD deficient pts
7. Steven Johnson syndrome
8. Photosensitivty
9. Allergic reactions- drug hypersensitivity
   * *** The higher the blood levels the higher the incidence of toxicity

Question 9

Co-Trimoxazole

Answer 9

Sulfa Drug, IV
Combination produce of trimethoprim and sulfamethoxazole (TMX-SMX) (1:5 RATIO)

DOC:

• uncomplicated UTI
• Morexella Catarrhalis infection

Second line (or more) tx:

• listeria (septeciema, and menigitis)
• widely used for otitis media
• can be used for H. influenzae in URI

Spectrum:

• Active against MSSA and MRSA S. aureua
• respiratory tract infections - pneuococcus, h. influenzae, moraxella, legionella and klebsiella
• • not mycoplasma
• P. jirovecci Pneumonia
• some non TB mycobacterial infections
• Shigella
• Systemic salmonella
• UTI
• Prostatitis

Question 10

Sulfadiazine

Answer 10

Sulfa drug, Oral, intermediate duration
Tx: toxoplasmosis (used in combination with pyrimethamine)
- limited to serious infections because of inc. propensity to cause crystalluria

Question 11

Trimethoprim

Answer 11

Sulfa Drug
MOA: prevents the reduction of dihyrofolate into tertrahydrofolate (via dihydrofolate reductase)
Tx:
- UTI (and for prophylaxis)
- travelers diarrhea
- pheumoncystis carinii (combined with dapsone or sulfmethoxazole)
Spectrum: Activity against gram + and gram -

** can be used safely in patients who have impaired renal function or in those who cannot tolerate sulfa drugs

CI:
- do not use in pregnancy- folate inhibitor

Question 12

Silver Sulfadiazine

Answer 12

Sulfa drug, topical - resistricted to conjunctival sac, vag etc.
MOA: damages the cell membrane or wall—does not inhibit folic acid synthesis

Tx:
- tx and prevent skin infections caused by burns

spectrum

• bacteria and yeast
• -=> does not inhibit Carbonic anhydrase - so can be used when CA inhibitors are CI
• –> does not stain dressing and tissues

compare to manefide (only effective against bacteria) and silver nitrate (stains tissues and dressing)

Question 13

Sulfasalazine

Answer 13

Sulfa drug- oral
Prodrug- cleaved into active componeents in teh GI
combination of mesalamine and sulfapyridine
TX: UC (because of the mesalamine)