Pharmacology of Sulfonamides

What is the primary mechanism of action of sulfonamides?

How are sulfonamides primarily metabolized in the body?

Which of the following is TRUE regarding the excretion of sulfonamides?

Which sulfonamide is typically used in combination with trimethoprim for its synergistic effect?

What is the characteristic of sulfonamides in terms of their classification?

Sulfonamides

Synthetic bacteriostatic antibiotics
Inhibit folic acid synthesis in bacteria, which is necessary for nucleic acid (DNA and RNA) synthesis
Competitive inhibitors of the enzyme dihydropteroate synthase
Prevent the conversion of p-aminobenzoic acid (PABA) into dihydrofolic acid
Inhibit bacterial growth

Pharmacokinetics

Well absorbed orally
Can be administered topically or intravenously
Distribute well into body fluids, including cerebrospinal fluid (CSF) and the placenta
Bound variably to plasma proteins
Metabolized by the liver via acetylation
Excreted via the kidneys, partly unchanged in the urine
Can crystallize in the urine, leading to crystalluria

Classification

Short-acting:
- Example: Sulfadiazine, Sulfisoxazole
- Used for simple UTIs or in combination for more serious infections.
Intermediate-acting:
- Example: Sulfamethoxazole
- Often combined with trimethoprim (e.g., in cotrimoxazole) for synergistic effect.
Long-acting:
- Example: Sulfadoxine
- Used in combination with pyrimethamine as an antimalarial agent.
Topical agents:
- Example: Silver sulfadiazine and sulfacetamide
  - Silver sulfadiazine is used in treating burn wounds.
  - Sulfacetamide is used in treating eye infections.

This quiz examines the pharmacology of sulfonamides, synthetic bacteriostatic antibiotics that inhibit folic acid synthesis in bacteria. It covers their mechanisms, pharmacokinetics, and classification into short-acting and intermediate-acting types. Test your knowledge of these important medications used to treat bacterial infections.