The first antimicrobial drugs that were used to treat bacterial infections in humans were known as sulfa drugs—synthetic medications created from a crystalline compound called sulfanilamide. Sulfa drugs saved countless lives in the 20th century and paved the way for modern antibiotics.

In the early 1930s, German scientists realized that a red dye called prontosil prevented the growth of Streptococcus bacteria in mice. In fact, the dye seemed to protect against all types of infections, including blood diseases, childbed fever (infection of the uterus), and the skin condition erysipelas (also known as St. Anthony’s fire). The researchers discovered that the active ingredient in this reaction was sulfanilamide. Over the next decade, medicines derived from the sulfanilamide molecule, commonly known as sulfa drugs, became the only widely available antibiotics. They were standard in first-aid kits during World War II and are credited with saving the lives of tens of thousands of patients, including Franklin Delano Roosevelt’s son, Franklin Delano Roosevelt Jr. (1914–1988), and Winston Churchill (1874–1965).

Unlike antibiotics, sulfa drugs do not kill bacteria—they merely limit their growth. This is called bacteriostatic activity, and it allows the body’s immune system to fight them more readily (see Immunity, page 2). The drugs disrupt the synthesis of folic acid, a B vitamin present in all living cells. This can stop the growth of invading bacteria (which need to make their own folic acid to survive) without harming healthy host cells (because humans and other mammals obtain folic acid through their diets instead of making it internally)—a principle known as selective toxicity.

Sulfur, by itself, is not toxic to the body. However, about 3 percent of people are highly allergic to relatives of sulfur, such as sulfites and sulfa drugs. For these people, sulfa drugs can cause skin rashes, high fever, headache, fatigue, and gastric problems. With the introduction of less-toxic derivatives and the mass production of penicillin in the 1940s, the widespread use of sulfa drugs declined. Today, they are used to treat pneumonia in AIDS patients, acne, urinary and vaginal infections, skin burns, and malaria and are receiving renewed interest in light of newer, drug- resistant strains of bacteria.

ADDITIONAL FACTS

  1. The German company IG Farben (which then owned what’s now Bayer) hoped to exclusively market sulfanilamide, but the compound had actually been used in the dye industry since 1906. Its patent had expired, making the drug available to anyone.
  2. Hundreds of manufacturers tried to strike it rich in the 1930s by producing tens of thousands of tons of sulfa drugs, sometimes with little care for safety or quality. As a result, at least 100 people were poisoned with diethylene glycol in the Elixir Sulfanilamide disaster of 1937, leading to the passage of the Federal Food, Drug, and Cosmetic Act in 1938.
  3. The first recorded use of a sulfa drug in the United States was for a 10-year-old girl with meningitis in July 1935. After an apparent cure, the patient suffered a relapse a few months later and died.