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Chapter 87

Chapter 87. Sulfonamides and Trimethoprim. Sulfonamides and Trimethoprim. Broad-spectrum antibiotics Both have closely related mechanisms Suppress bacterial growth by inhibiting tetrahydrofolic acid. Sulfonamides. First drugs available for systemic treatment of bacterial infections

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Chapter 87

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  1. Chapter 87 Sulfonamides and Trimethoprim

  2. Sulfonamides and Trimethoprim • Broad-spectrum antibiotics • Both have closely related mechanisms • Suppress bacterial growth by inhibiting tetrahydrofolic acid

  3. Sulfonamides • First drugs available for systemic treatment of bacterial infections • More effective and less toxic drugs now available • Inhibit the synthesis of folic acid (folate) • Mammalian cells do not manufacture their own folate (not affected like bacteria are affected) • Primary use now – for urinary tract infections • Other uses: nocardiosis, Chlamydia trachomatis, conjunction therapy for toxoplasmosis/malaria, ulcerative colitis

  4. Sulfonamides • Adverse effects • Hypersensitivity reactions – Stevens-Johnson syndrome • Hematologic effects • Kernicterus • Renal damage from crystalluria • Drug interactions • Metabolism-related interactions • Allergy-inducing drugs

  5. Fig.87-1. Structural relationships among sulfonamides, PABA, and folic acid.

  6. Fig.87-2. Sites of action of sulfonamides and trimethoprim. Sulfonamides and trimethoprim inhibit sequential steps in the synthesis of tetrahydrofolic acid (FAH4). In the absence of FAH4, bacteria are unable to synthesize DNA, RNA, and proteins.

  7. Trimethoprim (Proloprim and Trimpex) • Inhibits dihydrofolate reductase • Uses • Acute and uncomplicated urinary tract infections • Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Enterobacter, coagulase-negative Staphylococcus • Adverse effects • Hematologic effects • Use in pregnancy and lactation

  8. Trimethoprim-Sulfamethoxazole • The trimethoprim-sulfamethoxazole (TMP-SMZ) combo inhibits sequential steps in bacterial folic acid synthesis, making it much more powerful than TMP or SMZ alone. • Therapeutic uses • Urinary tract infection, otitis media, bronchitis, Shigellosis, pneumonia by Pneumocystis jiroveci, Pneumocystis pneumoniae, and GI infections

  9. Trimethoprim-Sulfamethoxazole • Adverse effects • Gastrointestinal • Nausea and vomiting • Rash • Hypersensitivity reactions (Stevens-Johnson syndrome) • Blood dyscrasias • Kernicterus • Renal damage – crystalluria

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