ABSTRACT
The sulfonamide (sulphonamide) antibacterial drugs, sulfapyridine (SP) and sulfamethoxypyridazine (SMP) are structurally related to para-aminobenzoic acid (PABA). Sulfonamides do not affect human cells by this mechanism, as they require pre-formed folic acid. Enzyme inhibition is reversible, so sulfonamides have bacteriostatic rather than bactericidal activity. They are rarely used as antibiotics nowadays due to adverse effects and bacterial resistance, with resistance to one sulfonamide conferring resistance to all. Sulfonamides are slowly and incompletely absorbed from the gastrointestinal tract and do not undergo first-pass metabolism. They are protein-bound to variable degrees in the circulation, and unbound sulfonamide diffuses throughout the body, especially to sites of inflammation. The clinical response should be assessed within 2 weeks, and dosage should be adjusted as necessary. The sulfonamide chemical moiety is present in a range of other non-antimicrobial drugs, including certain diuretics, sulfonylureas and cyclo-oxygenase 2 inhibitors.
