Sulfa

Sulfa Drugs

Sulfa drugs, also known as sulfonamides, are a group of synthetic antimicrobial agents that contain the sulfonamide group. They were the first antibiotics to be used systemically and paved the way for the antibiotic revolution in medicine.

History

The discovery of sulfa drugs dates back to the early 20th century. The first sulfa drug, Prontosil, was discovered by Gerhard Domagk in 1932. This discovery earned him the Nobel Prize in Physiology or Medicine in 1939. Prontosil was found to be effective against streptococcal infections in mice and later in humans.

Mechanism of Action

Sulfa drugs work by inhibiting the bacterial enzyme dihydropteroate synthase, which is involved in the synthesis of folate. Folate is essential for bacterial growth and replication, and its inhibition leads to the bacteriostatic effect of sulfa drugs. This mechanism is specific to bacteria, as humans obtain folate from their diet and do not synthesize it.

Clinical Uses

Sulfa drugs are used to treat a variety of bacterial infections, including:

• Urinary tract infections
• Respiratory tract infections
• Gastrointestinal infections
• Skin infections

They are also used in combination with other drugs to treat certain conditions, such as:

• Sulfamethoxazole/trimethoprim (Bactrim) for Pneumocystis jirovecii pneumonia
• Sulfadiazine with pyrimethamine for toxoplasmosis

Side Effects

Common side effects of sulfa drugs include:

• Allergic reactions, such as rash and fever
• Nausea and vomiting
• Photosensitivity

Serious side effects can include:

• Stevens-Johnson syndrome
• Toxic epidermal necrolysis
• Agranulocytosis

Resistance

Bacterial resistance to sulfa drugs has been a growing concern. Resistance mechanisms include:

• Mutation in the target enzyme, dihydropteroate synthase
• Increased production of para-aminobenzoic acid (PABA), which competes with sulfa drugs
• Efflux pumps that remove the drug from bacterial cells

Also see

• Antibiotics
• Penicillin
• Cephalosporins
• Antimicrobial resistance