This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti Microbial, Subject name: Pharmacology
[{'content': 'Longest acting sulphonamide is - \nSelect and explain. \nA. Sulphadiazine, B. Sulfacytidine, C. Sulfamethoxazole, D. Sulfadoxine', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans, is 'd' i.e., Sulfadoxine Sulfonamideso Sulfonamides are bacteriostatic and act by inhibiting folic acid synthesis by inhibiting enzyme folate synthatase.o Bacteria synthesize their own folic acid of wTtich para aminobenzoic acid (PABA) is a constituent - Sulfonamides, being structural analogues of PABA, inhibit bacterial folate synthase competitively.o Sulfonamides are not effective in presence of pus and tissue extract because - (1) Pus contains purines and thymidine which decrease bacterial requirement for folic acid and (2) Pus is rich in PABA.Classification1. Short acting - Sulfadiazine, Sulfisoxaxole, Sulfamethizole, Sulfacystine.Intermediate acting - Sulfamethoxazole.Long acting - Sulfadoxine, Sulfamethopyrazine.Topical Sulfonamides - Sulfacetamide sodium, Mafenide, silver sulfadiazine.Sulfonamide for RA and ulcerative colitis - Sulfasalazine.o Sulfadoxine is Longest acting whereas sulfacytidine is shortest acting sulphonamide.", 'role': 'assistant'}]