Sulfonamides Flashcards
Name the sulfonamides
Sulfisoxazole Sulfadiazine Sulfamethoxazole Sulfazalazine Sulfadoxine
How do sulfonamides work?
Inhibit folate production and incorporation into purines and prevents DNA synthesis
What are the indications for sulfonamides?
UTI’s
Otitis media
Upper respiratory infections
Soft tissue infections
Are sulfonamides bacteriostatic or bacteriocidal?
Bacteriostatic
Cidal in combination with trimethoprim
Sulfonamides inhibit ….
Trimethoprim inhibits…
Sulfonamides inhibit dihydropteroate synthase
Trimethoprim inhibits folate reductase
Sulfonamides are a structural analog of…
PABA
Which sulfonamide is used in malaria?
Sulfadoxine combined with pyrimethamine
Which sulfonamide has the longest half life?
Sulfadoxine (7-9 days)
Which sulfonamides have short half lives?
Sulfasalazine, Sulfisoxazole
6-10 hours
Which sulfonamide remains in the lumen?
Sulfasalazine
Which sulfonamides have intermediate half-lives?
Sulfadiazine (10-17 hours)
Sulfamethoxazole (+ Trimethoprim) (11 hours)
Which sulfonamides are oral OR IV?
Sulfadiazine
Sulfamethoxazole+Trimethoprim
Which sulfonamide is topical use?
Sulfacetamide
What counseling point should be made with sulfonamides?
Stay hydrated!!
Drug could crystallize in the urine
How are sulfonamides excreted?
In the urine - 10 to 20 times concentrated compared to the plasma
Why is sulfasalazine different?
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
What toxicities are associated with sulfonamides?
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
What are the 4 types of allergic reactions? What do sulfonamides cause?
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)
Why do sulfonamides cause Hematopoietic disturbances?
Decreased glucose-6-phosphate can cause hemolytic anemia
Decreased potassium and magnesium can cause electrolyte abnormalities
What drug interactions do we worry about with sulfonamides?
Plasma binding (competition) Compete for acetylation enzymes
What causes resistance in sulfonamides?
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)
What is trimethoprim?
Trimethoprim inhibits dihydrofolate reductase
Often combined with sulfonamide Sulfamethoxazole in Bactrim/Septra in 5:1 ratio (20:1 ratio in blood)
What is trimethoprim used for?
Combo product of trimethoprim/sulfamethoxazole is used in:
UTI’s
Otitis media
Bronchitis
Used to treat pneumocystis jiroveci in AIDs patients
What benefit does septra have over penicillins?
Oral suspension doesn’t need refrigeration
What toxicities are associated with trimethoprim?
Hematopoietic problems if folate deficient
GI disturbances
Hepatitis
Exfoliative dermatitis
