Sulfamethoxazole

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Chemical Structure / Formula of Sulfamethoxazole

• Formula: C10H11N3O3S

• Structure: Isoxazole-containing sulfonamide.

Mechanism of Action

• Inhibits dihydropteroate synthase, blocking folic acid synthesis.

Uses

• UTIs, respiratory tract infections (combined with trimethoprim = Cotrimoxazole).

Side Effects

• Hypersensitivity reactions, crystalluria, nephrotoxicity.

Synthesis of Sulfamethoxazole

Structure-Activity Relationship (SAR) of Sulfamethoxazole

Structural Feature	SAR Insight
5-methylisoxazole ring	Enhances absorption and distribution.
p-Aminobenzenesulfonamide core	Required for enzyme binding and activity.
Used synergistically with trimethoprim	Blocks sequential steps in folate synthesis.

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