Sulphonide Flashcards
What is the mechanism of action of sulfonamides?
Sulfonamides inhibit p-aminobenzoic acid (PABA) cellular uptake and incorporation into folic acid, preventing nucleic acid synthesis and bacterial growth and multiplication.
Why do sulfonamides not harm human cells?
Sulfonamides do not harm human cells because humans use preformed folic acid and do not synthesize folic acid.
What is the primary use of sulfasalazine, and why is it not absorbed when administered orally?
Sulfasalazine is used for the treatment of chronic inflammatory bowel disease (ulcerative colitis). It is not absorbed when administered orally because local intestinal flora split it into sulfapyridine and 5-aminosalicylate, with the latter exerting the anti-inflammatory effect.
What are the adverse effects of sulfonamides?
The adverse effects of sulfonamides include crystalluria, hypersensitivity reactions (rashes, angioedema, Stevens-Johnson syndrome), hematopoietic disturbances (hemolytic anemia, agranulocytosis, aplastic anemia), and kernicterus in newborns.
What is the role of trimethoprim in bacterial inhibition?
Trimethoprim is a potent inhibitor of bacterial dihydrofolate reductase, which prevents the conversion of dihydrofolic acid to tetrahydrofolic acid, thereby inhibiting DNA and RNA synthesis.
What is the combination of sulfamethoxazole and trimethoprim called, and why are they used together?
The combination is called co-trimoxazole. They are used together because of their synergistic activity, which converts two bacteriostatic compounds into a bactericidal effect, increases the antibacterial spectrum, and reduces the emergence of resistance.
What are the uses of co-trimoxazole?
Co-trimoxazole is used for urinary tract infections, respiratory tract infections, prostatitis, shigellosis, and invasive salmonella infections (typhoid fever).
What is the primary indication for sodium fusidate?
Sodium fusidate is primarily indicated for penicillin-resistant staphylococci, especially in osteomyelitis and staphylococcal endocarditis. It is also used locally for impetigo, folliculitis, and infective eczema.
What serious adverse effects are associated with co-trimoxazole?
Serious adverse effects of co-trimoxazole include Stevens-Johnson syndrome (a severe form of erythema multiforme) and bone marrow depression (agranulocytosis), especially in the elderly.
