Sulfa drug is any of a group of chemically related antibacterial compounds. Sulfa drugs, also called sulfonamides << suhl FON uh mydz >> , were the first drugs to be proved safe and effective against many common bacterial infections. Sulfa drugs played a major role in antibacterial treatment from the late 1930’s until the mid-1940’s, when penicillin became widely available. The development of sulfa drugs resulted in a sharp decline in the number of deaths caused by many infectious diseases. These drugs helped save many lives during World War II (1939-1945). Today, physicians prescribe sulfa drugs chiefly to treat urinary tract infections.
How sulfa drugs work.
Normally, sulfa drugs do not actually kill bacteria. Instead, they prevent the bacteria from multiplying. The bacteria are then killed by the body’s normal defense mechanisms.
Bacteria that are sensitive to sulfa drugs require a chemical called para-aminobenzoic acid (PABA) to multiply. Sulfa drugs have a chemical structure similar to PABA and are readily absorbed by bacteria that require this compound. The sulfonamides then block the chemical reactions that involve PABA, so that the bacteria can no longer divide and multiply.
Uses in treating diseases.
Sulfonamides are not effective against all bacteria. Therefore, physicians need to identify the type of bacteria causing an infection before they know whether to use a sulfa drug. Sulfa drugs are most commonly taken by mouth, but they may be given by injection or applied directly to the skin.
In the past, sulfa drugs were used in the treatment of such diseases as pneumonia, dysentery, septicemia (blood poisoning), cellulitis, plague, and conjunctivitis. The use of sulfa drugs has decreased because more powerful drugs—such as penicillin and other antibiotics—have been developed to treat many bacterial diseases. In addition, many bacteria have become resistant to sulfa drugs.
In the late 1960’s, researchers developed a combination drug consisting of sulfamethoxazole (a sulfonamide) and a compound called trimethoprim. This drug is effective in treating certain bacterial infections not sensitive to sulfonamides alone. Recurrent urinary tract infections, middle-ear infections, and shigellosis are among the diseases that may be treated with this drug.
Development of sulfa drugs.
In 1908, Paul Gelmo, a German chemist who was looking for better dyes for woolen goods, discovered chemicals that eventually led to sulfa drugs. But it was not until the early 1930’s that sulfonamides were used in medicine.
In 1935, a German pathologist named Gerhard Domagk reported that the dye Prontosil killed streptococcal bacteria in mice. Further research revealed that Prontosil was broken down to sulfanilamide in the body. Scientists determined that sulfanilamide was the chemical responsible for blocking the bacteria’s growth. Researchers tested thousands of related chemicals before they found the few that were most useful.
A major problem with sulfanilamide and other early sulfa drugs was that they sometimes crystallized (solidified) in the urine of the patient, causing kidney damage. Scientists later developed sulfa drugs that are much more water soluble and, therefore, much less likely to crystallize in the urine.
