9. Antimetabolites Flashcards
Sulfonamides are related to what other molecule?
p-Aminobenzoic acid (PABA)
Are sulfonamides bactericidal or bacteriostatic?
Bacteriostatic
Sulfonamides mechanism of action
Compete for enzyme dihydropteroate synthetase, preventing synthesis of bacterial folic acid
Deprives cell of essential cofactor purine, pyrimidine and AA synthesis
What enzyme do sulfonamides inhibit?
compete with PABA to inhibit dihydropteroate synthetase
What enzyme does trimethoprim/methotrexate inhibit?
Dihydrofolate reductase
What is the function of dihydrofolic reductase?
Reduces dihydrofolate to tetrahydorfolic acid which is necessary to produce thymidine and purines for nucleic acid synthesis and amino acids for protein synthesis
What 4 pathogen are most susceptible to sulfonamides?
Enterobacteriaceae (rod shaped bacteria)
Chlamydia (STI)
Nocardia (rod shaped bacteria often affecting lungs or causing systemic infections)
Toxoplasmosis (protozoan)
How are sulfonamides administered?
Well absorbed orally
Sulfazalazine absorbed orally or rectally
What conditions are sulfasalazine unique in treating?
Crohn’s dz
Ulcerative colitis
What are two therapeutic uses of sulfonamide?
UTI (used with trimethroprim) - E. coli
Nocardiosis (pneumonia and brain abscess in imunocompromised pts)
What are 4 adverse reactions of sulfonamides?
- Crystalluria
- Bladder stones
- Adequate water intake and akalinization of urine needed to reduce crystallization
- Hypersensitivity
- Rash
- Angioedema
- Stevens-Johnson
- Hemopoietic
- Hemolytic anemia
- Granulocytopenia
- Thrombocytopenia
- Kernicterus
- increased bilirubin, damage to brain of infants
What is Kernicterus?
Damage to the brain centers of infants caused by increased levels of unconjugated indirect bilirubin which is free to pass into the CNS
Never use sulfonamides in infants/babies
What are the drug interactions of sulfonamides?
- Displace drugs from binding sites on serum albumin and potentiate effects of displaced drugs
- Form complexes with formaldehyde
- do not give sulfonamide to pts with methenamine bc methanamine is an antibiotic that is hydrolized into formaldehyde
